Led flashlight k7 repair era circuit diagram. A few simple LED power circuits. How to repair a LED Chinese flashlight yourself. Do-it-yourself LED lamp repair instructions with visual photos and videos
For safety and the ability to continue active activities in the dark, a person needs artificial lighting. Primitive people parted the darkness, setting fire to tree branches, then came up with a torch and a kerosene stove. And only after the invention by the French inventor Georges Leklanshe in 1866 of a prototype of a modern battery, and in 1879 by Thomson Edison of an incandescent lamp, David Meisell had the opportunity to patent the first electric lamp in 1896.
Since then, nothing has changed in the electrical circuit of new flashlights, until in 1923 the Russian scientist Oleg Vladimirovich Losev found a connection between luminescence in silicon carbide and p-n junction, and in 1990 scientists failed to create an LED with a higher light output, which allows replacing a light bulb incandescent. The use of LEDs instead of incandescent lamps, due to the low power consumption of LEDs, made it possible to multiply the operating time of flashlights with the same capacity of batteries and accumulators, increase the reliability of flashlights and practically remove all restrictions on the area of their use.
The LED rechargeable flashlight that you see in the photo came to me for repair with a complaint that the Chinese flashlight Lentel GL01 bought the other day for $ 3 does not shine, although the battery charge indicator is on.
External examination of the lantern made a positive impression. High-quality molding of the body, comfortable handle and switch. The rods of the plug for connecting to the household network for charging the battery are made retractable, which eliminates the need to store the power cord.
Attention! When disassembling and repairing the lantern, if it is connected to the mains, care should be taken. Touching unprotected parts of the body to uninsulated wires and parts can result in electric shock.
How to disassemble Lentel GL01 LED rechargeable flashlight
Although the flashlight was subject to warranty repair, but remembering my walks during the warranty repair of a failed electric kettle (the kettle was expensive and the heating element burned out in it, so it was not possible to repair it with my own hands), I decided to do the repairs myself.
Disassembling the headlight was easy. It is enough to turn the ring that fixes the protective glass a small angle counterclockwise and pull it off, then unscrew a few screws. It turned out that the ring is fixed on the body with a bayonet connection.
After removing one of the halves of the flashlight housing, access to all its nodes appeared. On the left in the photo you can see a printed circuit board with LEDs, to which a reflector (light reflector) is attached with three self-tapping screws. In the center is a black battery with unknown parameters, there is only a marking for the polarity of the terminals. To the right of the battery is the printed circuit board of the charger and indication. On the right is a power plug with retractable rods.
Upon closer examination of the LEDs, it turned out that there were black spots or dots on the emitting surfaces of the crystals of all LEDs. It became clear even without checking the LEDs with a multimeter that the flashlight does not shine due to their burnout.
There were also blackened areas on the crystals of two LEDs installed as backlight on the battery charging indication board. In LED lamps and tapes, one LED usually fails, and acting as a fuse, it protects the rest from burning out. And in the lantern, all nine LEDs failed at the same time. The voltage on the battery could not increase to a value that could disable the LEDs. To find out the reason, I had to draw an electrical circuit diagram.
Finding the cause of the failure of the lantern
The electrical circuit of the lantern consists of two functionally completed parts. The part of the circuit located to the left of switch SA1 performs the function of a charger. And the part of the circuit, shown to the right of the switch, provides a glow.
The charger works as follows. The voltage from the 220 V household network is supplied to the current-limiting capacitor C1, then to the bridge rectifier, assembled on diodes VD1-VD4. The rectifier supplies voltage to the battery terminals. Resistor R1 serves to discharge the capacitor after removing the flashlight plug from the network. Thus, an electric shock from the discharge of a capacitor is excluded in the event of an accidental touch by hand at the same time of two pins of the plug.
The LED HL1, connected in series with the current-limiting resistor R2 in the opposite direction with the upper right diode of the bridge, as it turned out, always glows when the plug is inserted into the network, even if the battery is faulty or disconnected from the circuit.
The SA1 operating mode switch is used to connect individual groups of LEDs to the battery. As can be seen from the diagram, it turns out that if the flashlight is connected to the mains for charging and the switch slider is in position 3 or 4, then the voltage from the battery charger also goes to the LEDs.
If a person turns on the flashlight and finds that it does not work, and, not knowing that the switch engine must be set to the “off” position, which is not mentioned in the instruction manual for the flashlight, connects the flashlight to the mains for charging, then at the expense voltage surge at the output of the charger, the LEDs will get a voltage that is much higher than the calculated one. More current will flow through the LEDs and they will burn out. With the aging of an acid battery due to the sulfitation of lead plates, the battery charge voltage increases, which also leads to burnout of the LEDs.
Another circuit design that surprised me is the parallel connection of seven LEDs, which is unacceptable, since the current-voltage characteristics of even LEDs of the same type are different and therefore the current passing through the LEDs will also not be the same. For this reason, when choosing the value of the resistor R4 based on the maximum allowable current flowing through the LEDs, one of them can be overloaded and fail, and this will lead to an overcurrent of the LEDs connected in parallel, and they will also burn out.
Alteration (modernization) of the electrical circuit of the lantern
It became obvious that the breakdown of the lantern was due to mistakes made by the developers of its electrical circuit diagram. To repair the lamp and prevent its re-breakdown, it is necessary to redo it by replacing the LEDs and make minor changes to the electrical circuit.
In order for the battery charge indicator to actually signal its charging, the HL1 LED must be turned on in series with the battery. A few milliamps of current is required to light up the LED, and the current output by the charger should be about 100 mA.
To ensure these conditions, it is enough to disconnect the HL1-R2 circuit from the circuit in the places indicated by red crosses and install an additional resistor Rd with a nominal value of 47 ohms with a power of at least 0.5 W in parallel with it. The charge current flowing through Rd will create a voltage drop of about 3 V on it, which will provide the necessary current for the HL1 indicator to glow. At the same time, the connection point of HL1 and Rd must be connected to terminal 1 of the switch SA1. In such a simple way, the possibility of supplying voltage from the charger to the EL1-EL10 LEDs during battery charging will be excluded.
To equalize the magnitude of the currents flowing through the EL3-EL10 LEDs, it is necessary to exclude the R4 resistor from the circuit and connect a separate 47-56 Ohm resistor in series with each LED.
Electrical diagram after revision
Minor changes made to the circuit increased the information content of the charge indicator of an inexpensive Chinese LED flashlight and greatly increased its reliability. I hope that the manufacturers of LED lamps after reading this article will make changes to the electrical circuits of their products.
After modernization, the electrical circuit diagram took the form as in the drawing above. If it is necessary to illuminate the flashlight for a long time and does not require a high brightness of its glow, then you can additionally install a current-limiting resistor R5, due to which the flashlight's operating time without recharging will double.
Repair of LED rechargeable lamp
After disassembly, first of all, you need to restore the working capacity of the lantern, and then engage in modernization.
Checking the LEDs with a multimeter confirmed their malfunction. Therefore, all the LEDs had to be soldered and the holes for installing new diodes removed from the solder.
Judging by the appearance, lamp LEDs from the HL-508H series with a diameter of 5 mm were installed on the board. HK5H4U type LEDs from a linear LED lamp with similar technical characteristics were available. They were useful for repairing the lantern. When soldering the LEDs to the board, you must remember to observe the polarity, the anode must be connected to the positive terminal of the battery or battery.
After replacing the LEDs, the PCB was connected to the circuit. The brightness of the glow of some LEDs due to the common current-limiting resistor was somewhat different from others. To eliminate this shortcoming, it is necessary to remove the resistor R4 and replace it with seven resistors, including in series with each LED.
To select a resistor that provides the optimal mode of operation of the LED, the dependence of the current flowing through the LED on the value of the series-connected resistance at a voltage of 3.6 V, equal to the flashlight battery voltage, was measured.
Based on the conditions for using the lantern (in the event of interruptions in the supply of electricity to the apartment), high brightness and lighting range were not required, so the resistor was chosen with a nominal value of 56 ohms. With such a current-limiting resistor, the LED will work in light mode, and power consumption will be economical. If you want to squeeze out the maximum brightness from the flashlight, then you should use a resistor, as can be seen from the table, with a nominal value of 33 ohms and make two modes of operation of the flashlight by turning on another common current-limiting resistor (in the R5 diagram) with a nominal value of 5.6 ohms.
To connect a resistor in series with each LED, you must first prepare the printed circuit board. To do this, it needs to be cut on any one current-carrying track suitable for each LED and make additional contact pads. The current-carrying tracks on the board are protected by a layer of varnish, which must be scraped off with a knife blade to copper, as in the photograph. Then tin the bare contact pads with solder.
It is better and more convenient to prepare a printed circuit board for mounting resistors and solder them if the board is fixed on a standard reflector. In this case, the surface of the LED lenses will not be scratched, and it will be more convenient to work.
Connecting the diode board after repair and modernization to the flashlight battery showed sufficient for illumination and the same brightness of the glow of all LEDs.
I did not have time to repair the previous lamp, as the second one got into repair, with the same malfunction. I did not find information about the manufacturer and technical characteristics on the body of the flashlight, but judging by the handwriting of the manufacturer and the reason for the breakdown, the manufacturer is the same, Chinese Lentel.
According to the date on the body of the flashlight and on the battery, it was possible to establish that the flashlight was already four years old and, according to its owner, the flashlight worked flawlessly. Obviously, the flashlight lasted a long time thanks to the warning label "Do not turn on while charging!" on a hinged cover that closes the compartment in which the plug is hidden for connecting the flashlight to the mains to charge the battery.
In this flashlight model, the LEDs are included in the circuit according to the rules, a 33 ohm resistor is installed in series with each. The value of the resistor is easy to find out by color coding using an online calculator. Checking with a multimeter showed that all the LEDs are faulty, the resistors also turned out to be open.
An analysis of the reason for the failure of the LEDs showed that due to the sulfation of the acid battery plates, its internal resistance increased and, as a result, its charging voltage increased several times. During charging, the flashlight was turned on, the current through the LEDs and resistors exceeded the limit, which led to their failure. I had to replace not only the LEDs, but also all the resistors. Based on the above conditions of operation of the flashlight, resistors with a nominal value of 47 ohms were chosen for replacement. The resistor value for any type of LED can be calculated using an online calculator.
Alteration of the battery charging mode indication circuit
The flashlight has been repaired, and you can start making changes to the battery charge indication circuit. To do this, it is necessary to cut the track on the printed circuit board of the charger and indication in such a way that the HL1-R2 chain on the LED side is disconnected from the circuit.
The lead-acid AGM battery was brought to a deep discharge, and an attempt to charge it with a standard charger did not lead to success. I had to charge the battery using a stationary power supply with the function of limiting the load current. A voltage of 30 V was applied to the battery, while at the first moment it consumed only a few mA of current. Over time, the current began to increase and after a few hours increased to 100 mA. After a full charge, the battery was installed in the flashlight.
Charging deeply discharged lead-acid AGM batteries as a result of long-term storage with increased voltage allows them to restore their performance. The method has been tested by me on AGM batteries more than a dozen times. New batteries that do not want to be charged with standard chargers, when charged from a constant source at a voltage of 30 V, are restored to almost their original capacity.
The battery was discharged several times by turning on the flashlight in the operating mode and charged using the standard charger. The measured charge current was 123 mA, with a voltage at the battery terminals of 6.9 V. Unfortunately, the battery was worn out and it was enough to operate the flashlight for 2 hours. That is, the battery capacity was about 0.2 Ah, and for a long-term operation of the flashlight it is necessary to replace it.
HL1-R2 circuit on the PCB was well placed, and it took an angle to cut just one current-carrying track, as in the photograph. The cutting width must be at least 1 mm. Calculation of the value of the resistor and verification in practice showed that for the stable operation of the battery charging indicator, a resistor with a nominal value of 47 ohms with a power of at least 0.5 W is required.
The photo shows a printed circuit board with a soldered current limiting resistor. After such refinement, the battery charge indicator lights up only if the battery is actually charging.
Modernization of the operating mode switch
To complete the repair and modernization of the lamps, it is necessary to solder the wires at the switch terminals.
In models of repaired lamps, a four-position slide-type switch is used to turn on. The average conclusion in the above photo is a general one. When the switch slider is in the leftmost position, the common output is connected to the left output of the switch. When moving the switch engine from the extreme left position one position to the right, its common output is connected to the second output, and when the engine is moved further, to 4 and 5 outputs in series.
To the middle common terminal (see photo above) you need to solder the wire coming from the positive terminal of the battery. Thus, it will be possible to connect the battery to a charger or LEDs. You can solder a wire coming from the main board with LEDs to the first output, and a 5.6 Ohm current-limiting resistor R5 can be soldered to the second output to enable switching the flashlight to an energy-saving mode. Solder the conductor coming from the charger to the far right terminal. Thus, it will be impossible to turn on the flashlight while the battery is charging.
Repair and modernization
LED rechargeable flashlight-spotlight "Photon PB-0303"
Another copy from a series of Chinese-made LED lamps called the Photon PB-0303 LED spotlight came to be repaired. The flashlight did not react when the power button was pressed, an attempt to charge the flashlight battery using a charger did not lead to success.
The flashlight is powerful, expensive, costs about $20. According to the manufacturer, the luminous flux of the flashlight reaches 200 meters, the body is made of impact-resistant ABS plastic, the kit includes a separate charger and a shoulder strap.
The Photon LED flashlight has good maintainability. To gain access to the electrical circuit, it is enough to unscrew the plastic ring holding the protective glass by turning the ring counterclockwise when looking at the LEDs.
When repairing any electrical appliance, troubleshooting always begins with the power source. Therefore, the first step was to measure the voltage at the terminals of the acid battery using a multimeter turned on in the mode. It amounted to 2.3 V, instead of 4.4 V. The battery was completely discharged.
When the charger was connected, the voltage at the battery terminals did not change, it became obvious that the charger was not working. The flashlight was used until the battery was completely discharged, and then it was not used for a long time, which led to a deep discharge of the battery.
It remains to check the health of the LEDs and other elements. To do this, it was necessary to remove the reflector, for which six self-tapping screws were unscrewed. There were only three LEDs on the printed circuit board, a chip (microcircuit) in the form of a droplet, a transistor and a diode.
From the board and the battery, five wires went to the handle. In order to understand their connection, it was necessary to disassemble it. To do this, you need to unscrew the two screws inside the lantern with a Phillips screwdriver, which were located next to the hole into which the wires went.
To detach the lamp handle from its body, it must be moved away from the fastening screws. This must be done carefully so as not to tear the wires from the board.
As it turned out, there were no electronic elements in the pen. Two white wires were soldered to the outputs of the on / off button of the flashlight, and the rest to the connector for connecting the charger. A red wire was soldered to the 1st output of the connector (numbering conditional), which was soldered with the other end to the positive input of the printed circuit board. A blue-white conductor was soldered to the second contact, which was soldered with the second end to the negative pad of the printed circuit board. A green wire was soldered to terminal 3, the other end of which was soldered to the negative terminal of the battery.
electrical circuit diagram
Having dealt with the wires hidden in the handle, you can draw an electrical circuit diagram of the Photon flashlight.
From the negative terminal of the GB1 battery, voltage is supplied to pin 3 of connector X1 and then from its pin 2 through the blue-white conductor it goes to the printed circuit board.
Connector X1 is designed in such a way that when the charger plug is not inserted into it, pins 2 and 3 are connected to each other. When the plug is inserted, pins 2 and 3 are disconnected. Thus, automatic disconnection of the electronic part of the circuit from the charger is provided, which excludes the possibility of accidentally turning on the flashlight during battery charging.
From the positive terminal of the battery GB1, voltage is supplied to D1 (chip-chip) and the emitter of a bipolar transistor of the S8550 type. The CHIP performs only the function of a trigger, which allows the button to turn on or off the glow of the EL LEDs (⌀8 mm, glow color - white, power 0.5 W, current consumption 100 mA, voltage drop 3 V.) without fixation. When you first press the S1 button from the D1 chip, a positive voltage is applied to the base of the transistor Q1, it opens and the supply voltage is supplied to the LEDs EL1-EL3, the lamp turns on. When the button S1 is pressed again, the transistor closes and the lamp turns off.
From a technical point of view, such a circuit solution is illiterate, since it increases the cost of the flashlight, reduces its reliability, and in addition, up to 20% of the battery capacity is lost due to the voltage drop at the Q1 transistor junction. Such a circuit design is justified if it is possible to adjust the brightness of the light beam. In this model, instead of a button, it was enough to put a mechanical switch.
It was surprising that in the circuit the EL1-EL3 LEDs are connected in parallel to the battery like incandescent bulbs, without current-limiting elements. As a result, when turned on, a current passes through the LEDs, the value of which is limited only by the internal resistance of the battery, and when it is fully charged, the current may exceed the allowable for the LEDs, which will lead to their failure.
Checking the health of the electrical circuit
To check the health of the microcircuit, transistor and LEDs from an external power source with a current limiting function, a 4.4 V DC voltage was applied with polarity directly to the power pins of the printed circuit board. The current limit value was set to 0.5 A.
After pressing the power button, the LEDs lit up. After pressing it again, they went out. LEDs and a microcircuit with a transistor turned out to be serviceable. It remains to deal with the battery and charger.
Acid battery recovery
Since the acid battery with a capacity of 1.7 A was completely discharged, and the regular charger was faulty, I decided to charge it from a stationary power supply. When connecting the battery for charging to a power supply with a set voltage of 9 V, the charge current was less than 1 mA. The voltage was increased to 30 V - the current increased to 5 mA, and after an hour under this voltage it was already 44 mA. Further, the voltage was reduced to 12 V, the current dropped to 7 mA. After 12 hours of charging the battery at a voltage of 12 V, the current rose to 100 mA, and the battery was charged with this current for 15 hours.
The temperature of the battery case was within the normal range, which indicated that the charging current was used not to generate heat, but to store energy. After charging the battery and finalizing the circuit, which will be discussed below, tests were carried out. The flashlight with the restored battery illuminated continuously for 16 hours, after which the brightness of the beam began to fall, and therefore it was turned off.
Using the method described above, I had to repeatedly restore the performance of deeply discharged small-sized acid batteries. As practice has shown, only serviceable batteries, which have been forgotten for some time, are subject to recovery. Acid batteries that have exhausted their resource cannot be restored.
Charger repair
Measuring the voltage value with a multimeter on the contacts of the output connector of the charger showed its absence.
Judging by the sticker pasted on the adapter case, it was a power supply unit that outputs an unstabilized constant voltage of 12 V with a maximum load current of 0.5 A. There were no elements in the electrical circuit that limited the amount of charging current, so the question arose why charger used an ordinary power supply?
When the adapter was opened, a characteristic smell of burnt electrical wiring appeared, which indicated that the transformer winding had burned out.
The continuity of the primary winding of the transformer showed that it was open. After cutting the first layer of tape insulating the primary winding of the transformer, a thermal fuse was found, designed for a response temperature of 130°C. The test showed that both the primary winding and the thermal fuse were faulty.
It was not economically feasible to repair the adapter, since it was necessary to rewind the primary winding of the transformer and install a new thermal fuse. I replaced it with a similar one, which was at hand, with a DC voltage of 9 V. The flexible cord with the connector had to be soldered from a burned-out adapter.
The photo shows a drawing of the electrical circuit of the burned-out power supply unit (adapter) of the Photon LED flashlight. The replacement adapter was assembled according to the same scheme, only with an output voltage of 9 V. This voltage is quite enough to provide the required battery charge current with a voltage of 4.4 V.
For interest, I connected the flashlight to a new power supply and measured the charging current. Its value was 620 mA, and this is at a voltage of 9 V. At a voltage of 12 V, the current was about 900 mA, significantly exceeding the load capacity of the adapter and the recommended battery charge current. For this reason, the primary winding of the transformer burned out from overheating.
Refinement of the electrical circuit diagram
LED rechargeable flashlight "Photon"
To eliminate circuit technical violations in order to ensure reliable and long-term operation, changes were made to the lamp circuit and the printed circuit board was finalized.
The photo shows the electrical circuit diagram of the converted LED lamp "Photon". In blue, additionally installed radio elements are shown. Resistor R2 limits the battery charge current to 120 mA. To increase the charging current, you need to reduce the value of the resistor. Resistors R3-R5 limit and equalize the current flowing through the LEDs EL1-EL3 when the flashlight is on. The EL4 LED with a current-limiting resistor R1 connected in series is installed to indicate the process of charging the battery, since the developers of the flashlight did not take care of this.
To install current-limiting resistors on the board, the printed tracks were cut, as shown in the photo. The charge current limiting resistor R2 was soldered at one end to the contact pad, to which the positive wire from the charger was previously soldered, and the soldered wire was soldered to the second terminal of the resistor. An additional wire (yellow in the picture) was soldered to the same contact pad, designed to connect the battery charging indicator.
Resistor R1 and indicator LED EL4 were placed in the flashlight handle, next to the X1 charger connector. The anode lead of the LED was soldered to pin 1 of connector X1, and to the second pin, the cathode of the LED, a current-limiting resistor R1. A wire was soldered to the second output of the resistor (yellow in the photo), connecting it to the output of the resistor R2, soldered to the printed circuit board. Resistor R2, for ease of installation, could also be placed in the flashlight handle, but since it heats up when charging, I decided to place it in a freer space.
When finalizing the circuit, resistors of the MLT type with a power of 0.25 W were used, except for R2, which is designed for 0.5 W. EL4 LED is suitable for any type and color of glow.
This photo shows the operation of the charge indicator while the battery is charging. The installation of the indicator made it possible not only to monitor the process of charging the battery, but also to control the presence of voltage in the network, the serviceability of the power supply and the reliability of its connection.
How to replace a burnt chip
If suddenly the CHIP - a specialized unmarked microcircuit in the Photon LED lamp, or similar, assembled according to a similar scheme, fails, then to restore the lamp's performance, it can be successfully replaced with a mechanical switch.
To do this, remove the D1 chip from the board, and instead of the transistor key Q1, connect an ordinary mechanical switch, as shown in the above electrical diagram. The switch on the lamp body can be installed instead of the S1 button or in any other suitable place.
Repair and alteration of the LED lamp
14Led Smartbuy Colorado
The Smartbuy Colorado LED flashlight stopped turning on, although three AAA batteries were installed with new ones.
The waterproof case was made of anodized aluminum alloy, had a length of 12 cm. The flashlight looked stylish and was easy to use.
How to check the batteries in the LED flashlight for suitability
Repair of any electrical appliance begins with checking the power source, therefore, despite the fact that new batteries were installed in the flashlight, repairs should begin with checking them. In the Smartbuy flashlight, the batteries are installed in a special container, in which they are connected in series with the help of jumpers. In order to gain access to the batteries of the flashlight, you need to disassemble it by turning the back cover counterclockwise.
Batteries must be installed in the container, observing the polarity indicated on it. The polarity is also indicated on the container, so it must be inserted into the lamp body with the side on which the “+” sign is applied.
First of all, you need to visually check all the contacts of the container. If there are traces of oxides on them, then the contacts must be cleaned to a shine with sandpaper or the oxide should be scraped off with a knife blade. To prevent re-oxidation of the contacts, they can be lubricated with a thin layer of any machine oil.
Next, you need to check the suitability of the batteries. To do this, by touching the probes of the multimeter, included in the DC voltage measurement mode, it is necessary to measure the voltage at the contacts of the container. Three batteries are connected in series and each of them must produce a voltage of 1.5 V, therefore the voltage at the terminals of the container must be 4.5 V.
If the voltage is less than specified, then it is necessary to check the correct polarity of the batteries in the container and measure the voltage of each of them individually. Perhaps only one of them sat down.
If everything is in order with the batteries, then you need to insert the container into the lamp body, observing the polarity, tighten the cover and check it for operability. In this case, you need to pay attention to the spring in the cover, through which the supply voltage is transmitted to the lamp body and from it directly to the LEDs. There should be no signs of corrosion on its end face.
How to check the health of the switch
If the batteries are good and the contacts are clean, but the LEDs do not shine, then you need to check the switch.
The Smartbuy Colorado flashlight has a two-position sealed push-button switch that shorts out the wire coming from the positive terminal of the battery container. When the button is pressed for the first time, its contacts close, and when it is pressed again, it opens.
Since batteries are installed in the flashlight, you can also check the switch using a multimeter switched on in voltmeter mode. To do this, you need to rotate it counterclockwise, if you look at the LEDs, unscrew its front part and set it aside. Next, with one probe of the multimeter, touch the body of the flashlight, and the second to the contact, which is located deep in the center of the plastic part shown in the photo.
The voltmeter should show a voltage of 4.5 V. If there is no voltage, press the switch button. If it is correct, then the voltage will appear. Otherwise, the switch needs to be repaired.
Checking the health of the LEDs
If it was not possible to detect a malfunction at the previous steps of the search, then at the next stage it is necessary to check the reliability of the contacts supplying the supply voltage to the board with LEDs, the reliability of their soldering and serviceability.
The printed circuit board with the LEDs soldered into it is fixed in the head part of the lamp with the help of a steel spring-loaded ring, through which the supply voltage is simultaneously supplied to the LEDs from the negative terminal of the battery container through the lamp body. In the photo, the ring is shown from the side with which it presses the printed circuit board.
The retaining ring is fixed quite firmly, and it was possible to remove it only with the help of the device shown in the photo. Such a hook can be bent from a steel strip with your own hands.
After removing the retaining ring, the printed circuit board with LEDs, which is shown in the photo, was easily removed from the head of the lamp. The absence of current-limiting resistors immediately caught my eye, all 14 LEDs were connected in parallel and through a switch directly to the batteries. Connecting the LEDs directly to the battery is unacceptable, since the amount of current flowing through the LEDs is limited only by the internal resistance of the batteries and can damage the LEDs. At best, it will greatly reduce their lifespan.
Since all the LEDs in the flashlight were connected in parallel, it was not possible to check them with a multimeter switched on in the resistance measurement mode. Therefore, a DC supply voltage of 4.5 V was applied to the printed circuit board from an external source with a current limit of up to 200 mA. All LEDs lit up. It became obvious that the malfunction of the flashlight was due to poor contact of the printed circuit board with the fixing ring.
Current consumption of LED lamp
For interest, I measured the current consumption of LEDs from batteries when they were turned on without a current-limiting resistor.
The current was more than 627 mA. The flashlight is equipped with HL-508H type LEDs, the operating current of which should not exceed 20 mA. 14 LEDs are connected in parallel, therefore, the total current consumption should not exceed 280 mA. Thus, the current flowing through the LEDs exceeded the rated current by more than two times.
Such a forced mode of operation of the LEDs is unacceptable, as it leads to overheating of the crystal, and as a result, premature failure of the LEDs. An additional disadvantage is the rapid discharge of batteries. They will be enough, if the LEDs do not burn out earlier, for no more than an hour of operation.
The design of the flashlight did not allow soldering current-limiting resistors in series with each LED, so I had to install one common resistor for all LEDs. The value of the resistor had to be determined experimentally. To do this, the flashlight was powered by standard batteries and an ammeter was connected in series with a 5.1 Ohm resistor in the positive wire break. The current was about 200 mA. When installing a resistor of 8.2 ohms, the current consumption was 160 mA, which, as the test showed, is quite enough for good lighting at a distance of at least 5 meters. To the touch, the resistor did not heat up, so any power is suitable.
Alteration of the design
After the study, it became obvious that for reliable and durable operation of the flashlight, it is necessary to additionally install a current-limiting resistor and duplicate the connection of the printed circuit board with the LEDs and the fixing ring with an additional conductor.
If earlier it was necessary that the negative bus of the printed circuit board touched the body of the lamp, then in connection with the installation of a resistor, it was necessary to exclude contact. To do this, a corner was ground from the printed circuit board along its entire circumference, from the side of the current-carrying tracks, using a needle file.
To prevent the clamping ring from touching the current-carrying tracks when fixing the printed circuit board, four rubber insulators about two millimeters thick were glued to it with Moment glue, as shown in the photograph. Insulators can be made from any dielectric material, such as plastic or heavy cardboard.
The resistor was pre-soldered to the clamping ring, and a piece of wire was soldered to the extreme track of the printed circuit board. An insulating tube was put on the conductor, and then the wire was soldered to the second terminal of the resistor.
After a simple do-it-yourself upgrade of the flashlight, it began to turn on stably and the light beam illuminates objects well at a distance of more than eight meters. In addition, the battery life has more than tripled, and the reliability of the LEDs has increased many times over.
An analysis of the causes of failures of repaired Chinese LED lights showed that they all failed due to illiterately designed electrical circuits. It remains only to find out whether this was done intentionally in order to save on components and shorten the life of the flashlights (so that more people buy new ones), or as a result of the illiteracy of the developers. I'm leaning towards the first assumption.
Repair of the LED lamp RED 110
I got a flashlight with a built-in acid battery from a Chinese manufacturer of the RED trademark for repair. There were two emitters in the lantern: - with a beam in the form of a narrow beam and emitting scattered light.
The photo shows the appearance of the RED 110 flashlight. I immediately liked the flashlight. Convenient body shape, two modes of operation, a loop for hanging around the neck, a retractable plug for connecting to the mains for charging. In the lantern, the section of diffused light LEDs shone, but the narrow beam did not.
For repair, the black ring fixing the reflector was first unscrewed, and then one self-tapping screw was unscrewed in the loop area. The body is easily divided into two halves. All parts were fixed on self-tapping screws and were easily removed.
The charger circuit was made according to the classical scheme. From the network, through a current-limiting capacitor with a capacity of 1 μF, the voltage was applied to a rectifier bridge of four diodes and then to the battery terminals. The battery voltage was applied to the narrow beam LED through a 460 Ohm current-limiting resistor.
All parts were mounted on a single-sided printed circuit board. The wires were soldered directly to the pads. The appearance of the printed circuit board is shown in the photo.
10 side light LEDs were connected in parallel. The supply voltage was supplied to them through a common current-limiting resistor 3R3 (3.3 ohms), although according to the rules, a separate resistor must be installed for each LED.
An external examination of the narrow beam LED did not reveal any defects. When power was supplied through the flashlight switch from the battery, voltage was present at the LED terminals, and it heated up. It became obvious that the crystal was broken, and this was confirmed by a multimeter dial. The resistance was 46 ohms for any connection of the probes to the LED terminals. The LED was defective and needed to be replaced.
For convenience, wires were soldered from the LED board. After releasing the leads of the LED from the solder, it turned out that the LED was firmly held by the entire plane of the reverse side on the printed circuit board. To separate it, I had to fix the board in the desktop temples. Next, place the sharp end of the knife at the junction of the LED with the board and lightly hit the knife handle with a hammer. The LED bounced off.
Marking on the LED housing, as usual, was absent. Therefore, it was necessary to determine its parameters and select a suitable one for replacement. Based on the overall dimensions of the LED, the battery voltage and the value of the current-limiting resistor, it was determined that a 1 W LED (current 350 mA, voltage drop 3 V) would be suitable for replacement. From the "Reference Table of Popular SMD LED Parameters", a white LED6000Am1W-A120 LED was selected for repair.
The printed circuit board on which the LED is mounted is made of aluminum and at the same time serves to remove heat from the LED. Therefore, when installing it, it is necessary to ensure good thermal contact due to the tight fit of the back plane of the LED to the printed circuit board. To do this, before sealing, thermal paste was applied to the contact points of the surfaces, which is used when installing a radiator on a computer processor.
In order to ensure a snug fit of the LED plane to the board, you must first put it on a plane and slightly bend the leads up so that they recede from the plane by 0.5 mm. Next, tin the leads with solder, apply thermal paste and install the LED on the board. Next, press it against the board (it is convenient to do this with a screwdriver with the bit removed) and heat the leads with a soldering iron. Next, remove the screwdriver, press it with a knife at the bend of the output to the board and heat it with a soldering iron. After the solder has hardened, remove the knife. Due to the spring properties of the leads, the LED will be tightly pressed against the board.
When installing the LED, polarity must be observed. True, in this case, if a mistake is made, it will be possible to swap the voltage supply wires. The LED is soldered and you can check its operation and measure the current consumption and voltage drop.
The current flowing through the LED was 250 mA, the voltage drop was 3.2 V. From here, the power consumption (you need to multiply the current by the voltage) was 0.8 W. It was possible to increase the operating current of the LED by reducing the resistance to 460 ohms, but I did not do this, since the brightness of the glow was sufficient. But the LED will work in a lighter mode, heat up less and the flashlight's operating time from a single charge will increase.
Checking the heating of the LED worked for an hour showed effective heat dissipation. He heated up to a temperature of no more than 45 ° C. Sea trials showed a sufficient range of illumination in the dark, more than 30 meters.
Replacing the acid battery in the LED flashlight
An acid battery that has failed in a LED flashlight can be replaced with a similar acid battery, as well as lithium-ion (Li-ion) or nickel-metal hydride (Ni-MH) batteries of AA or AAA size.
Lead-acid AGM batteries of various dimensions without marking with a voltage of 3.6 V were installed in the repaired Chinese lanterns. According to the calculation, the capacity of these batteries is from 1.2 to 2 Ah.
On sale you can find a similar acid battery from a Russian manufacturer for UPS 4V 1Ah Delta DT 401, which has an output voltage of 4 V with a capacity of 1 Ah, costing a couple of dollars. To replace it is quite simple, observing the polarity, solder the two wires.
LED flashlight.
http://ua1zh. *****/led_driver/led_driver. htm
Autumn has come, it is already dark outside, and there were no light bulbs in the stairwell. I screwed it in ... The next day - again no. Yes, these are the realities of our life ... I bought a flashlight for my wife, but it turned out to be too big for her purse. I had to do it myself. The scheme does not claim to be original, but maybe it will fit someone - judging by the Internet_forums, interest in such a technique is not decreasing. I foresee possible questions - "Isn't it easier to take a ready-made microcircuit like the ADP1110 and not bother?" Yes, of course, much easier
that's just the cost of this chip in Chip & Dip 120 rubles, the minimum order is 10 pieces and the deadline is a month. The manufacture of this design took me exactly 1 hour and 12 minutes, including the time for prototyping, at a cost of 8 rubles per LED. The rest of a self-respecting radio amateur will always be found in the trash.
Actually the whole scheme:
Hhonestly, I will swear if someone asks - and on what principle does it all work?
And I will scold even moreif they ask for a seal...
Below is an example of the practical implementation of the design. For the case, a suitable box was taken from under some kind of perfumery. If desired, you can make the flashlight even more compact - everything is determined by the body used. Now I'm thinking of putting a flashlight into the case from a thick marker.
A little about the details: I took the KT645 transistor. Just got this handy. You can experiment with the selection of VT1, if you have time, and thereby slightly increase the efficiency, but it is hardly possible to achieve a radical difference with the applied transistor. The transformer is wound on a suitable ferrite ring with a high permeability with a diameter of 10 mm and contains 2x20 turns of PEL-0.31 wire. The windings are wound with two wires at once, it is possible without twisting - this is not a ShPTL ... Rectifier diode - any Schottky, capacitors - tantalum smd for a voltage of 6 volts. LED - any super-bright white for a voltage of 3-4 volts. When using a battery with a nominal voltage of 1.2 volts as a battery, the current through the LED I had was 18mA, and when using a dry battery with a nominal voltage of 1.5 volts, it was 22 ma, which provides maximum light output. In general, the device consumed approximately 30-35mA. Given the occasional use of the flashlight, the battery may well be enough for a year.
| When the battery voltage is applied to the circuit, the voltage drop across resistor R1 in series with the high brightness LED is 0V. Therefore, transistor Q2 is off and transistor Q1 is in saturation. The saturated state of Q1 turns on the MOSFET, thereby applying battery voltage to the LED through the inductor. As the current flowing through resistor R1 increases, this turns on transistor Q2 and turns off transistor Q1 and hence the MOSFET. During the MOSFET's off state, the inductance continues to provide power to the LED through the Schottky diode D2. The HB LED is a 1W Lumiled white LED. Resistor R1 helps control the brightness of the LED. Increasing the value of the resistor R1 reduces the brightness of the glow. http://www. *****/shem/schematics. html? di=55155 |
Making a modern flashlight
http://www. *****/schemes/contribute/constr/light2.shtml
Rice. 1. Schematic diagram of the current stabilizer
Using the circuit (Fig. 1) of a pulsed current stabilizer, which has long been known in amateur radio circles, using modern available radio components, you can assemble a very good LED flashlight.
For revision and alteration, the author purchased an outbred flashlight with a 6 V 4 Ah battery, with a “searchlight” on a 4.8 V 0.75 A lamp and a source of diffused light on a 4 W LDS. The "native" incandescent bulb turned black almost immediately due to operation at high voltage and failed after several hours of operation. A full charge of the battery at the same time was enough for 4-4.5 hours of work. Turning on the LDS generally loaded the battery with a current of about 2.5 A, which led to its discharge after 1-1.5 hours.
To improve the flashlight on the radio market, white LEDs of an unknown brand were purchased: one with a 30o beam and a working current of 100 mA for the “spotlight” and a dozen matte LEDs with a working current of 20 mA to replace the LDS. According to the scheme (Fig. 1), a stable current generator was assembled, having an efficiency of about 90%. The stabilizer circuitry made it possible to use a regular switch to switch the LEDs. The LED2 indicated in the diagram is a battery of 10 parallel connected identical white LEDs, rated for 20 mA each. Parallel connection of LEDs seems not entirely appropriate due to the nonlinearity and steepness of their CVC, but experience has shown that the spread of LED parameters is so small that even with this inclusion, their operating currents are almost the same. The only important thing is the complete identity of the LEDs; if possible, they should be bought “from one factory package”.
After refinement, the “spotlight” of course became a little weaker, but it is quite sufficient, the ambient light mode has not visually changed. But now, due to the high efficiency of the current stabilizer, when using the directional mode, the battery consumes a current of 70 mA, and in the scattered light mode, that is, the flashlight can work without recharging for about 50 or 25 hours, respectively. Brightness does not depend on the degree of discharge of the battery due to current stabilization.
The current stabilizer circuit works as follows: When power is applied to the circuit, transistors T1 and T2 are locked, T3 is open, because an unlocking voltage is applied to its gate through resistor R3. Due to the presence of an inductor L1 in the LED circuit, the current increases smoothly. As the current in the LED circuit increases, the voltage drop across the R5-R4 chain increases, as soon as it reaches about 0.4 V, transistor T2 opens, followed by T1, which in turn closes the current switch T3. The increase in current stops, a self-induction current arises in the inductor, which begins to flow through the diode D1 through the LED and the chain of resistors R5-R4. As soon as the current decreases below a certain threshold, transistors T1 and T2 will close, T3 will open, which will lead to a new cycle of energy accumulation in the inductor. In normal mode, the oscillatory process occurs at a frequency of the order of tens of kilohertz.
About details: there are no special requirements for details, you can use any small-sized resistors and capacitors. Instead of the IRF510 transistor, you can use the IRF530, or any n-channel field-effect switching transistor for a current of more than 3 A and a voltage of more than 30 V. The diode D1 must be with a Schottky barrier for a current of more than 1 A, if you put a conventional even high-frequency type KD212, the efficiency will decrease up to 75-80%. The inductor can be homemade, it is wound with a wire no thinner than 0.6 mm, better - with a bundle of several thinner wires. About 20-30 turns of wire on the B16-B18 armor core are required with a non-magnetic gap of 0.1-0.2 mm or close to 2000NM ferrite. If possible, the thickness of the non-magnetic gap is selected experimentally according to the maximum efficiency of the device. Good results can be obtained with ferrites from imported inductors installed in switching power supplies and also in energy-saving lamps. Such cores have the form of a thread spool, do not require a frame and a non-magnetic gap. Coils on toroidal cores made of pressed iron powder, which can be found in computer power supplies (they are wound with output filter inductors), work very well. The non-magnetic gap in such cores is evenly distributed in volume due to the production technology.
The same stabilizer circuit can also be used in conjunction with other batteries and batteries of galvanic cells with a voltage of 9 or 12 volts without any change in the circuit or cell ratings. The higher the supply voltage, the less current the flashlight will consume from the source, its efficiency will remain unchanged. The stabilization current is set by resistors R4 and R5. If necessary, the current can be increased up to 1 A without the use of heat sinks on the parts, only by selecting the resistance of the setting resistors.
The charger for the battery can be left "native" or assembled according to any of the known schemes, or even use an external one to reduce the weight of the flashlight.
The device is assembled by surface mounting in the free cavities of the flashlight body and filled with hot-melt adhesive for sealing.
It’s also a good idea to add a new device to the flashlight: an indicator of the degree of battery charge (Fig. 2).
Rice. 2. Schematic diagram of the indicator of the degree of charge of the battery.
The device is essentially a voltmeter with a discrete LED scale. This voltmeter has two modes of operation: in the first, it evaluates the voltage on the battery being discharged, and in the second, the voltage on the battery being charged. Therefore, in order to correctly assess the degree of charge for these modes of operation, different voltage ranges are selected. In the discharge mode, the battery can be considered fully charged when the voltage on it is 6.3 V, when it is completely discharged, the voltage drops to 5.9 V. In the process of charging the voltages are different, the battery is considered fully charged, the voltage at the terminals of which is 7, 4 V. In this regard, an algorithm for the operation of the indicator has been developed: if the charger is not connected, that is, at the “+ Charge.” there is no voltage, the "orange" crystals of the two-color LEDs are de-energized and the transistor T1 is locked. DA1 generates a reference voltage determined by the resistor R8. The reference voltage is supplied to the line of comparators OP1.1 - OP1.4, on which the voltmeter itself is implemented. To see how much charge is left in the battery, you must press the S1 button. In this case, the supply voltage will be applied to the entire circuit and, depending on the voltage on the battery, a certain number of green LEDs will light up. When fully charged, the entire column of 5 green LEDs will light up, when fully discharged, only one, the lowest LED. If necessary, the voltage is adjusted by selecting the resistance of the resistor R8. If the charger is turned on, through the terminal "+ Charge." and diode D1 voltage is supplied to the circuit, turning on the "orange" parts of the LEDs. In addition, T1 opens and connects resistor R9 in parallel with resistor R8, as a result of which the reference voltage generated by DA1 increases, which leads to a change in the comparator thresholds - the voltmeter is tuned to a higher voltage. In this mode, all the time while the battery is charging, the indicator displays the process of charging it also with a column of luminous LEDs, only this time the column is orange.
Homemade flashlight with LEDs
The article is dedicated to amateur radio tourists, and to everyone who in one way or another faced the problem of an economical source of lighting (for example, tents at night). Although lately you will not surprise anyone with LED flashlights, I will still share my experience in creating such a device, and also try to answer the questions of those who want to repeat the design.
Note: the article is designed for "advanced" radio amateurs who know Ohm's law well and hold a soldering iron in their hands.
The purchased flashlight "VARTA" powered by two AA batteries was taken as a basis:
https://pandia.ru/text/78/440/images/image006_50.jpg" width="600" height="277 src=">
And here is what the assembled circuit looks like:
"reference" points are the legs of the DIP chip.
A few explanations for the circuit: Electrolytic capacitors - tantalum CHIP. They have a low series resistance, which improves efficiency somewhat. Schottky diode - SM5818. Chokes had to be connected in parallel, because there was no suitable rating. Capacitor C2 - K10-17b. LEDs - superbright white L-53PWC "Kingbright". As you can see in the figure, the whole circuit easily fit into the empty space of the light emitting node.
The output voltage of the stabilizer in this switching circuit is 3.3V. Since the voltage drop across the diodes in the nominal current range (15-30mA) is about 3.1V, the extra 200mV had to be sown on a resistor connected in series with the output. In addition, a small series resistor improves load linearity and circuit stability. This is due to the fact that the diode has a negative TCR, and when it is heated, the direct voltage drop decreases, which leads to a sharp increase in current through the diode when it is powered from a voltage source. It was not necessary to equalize the currents through the diodes connected in parallel - no difference in brightness was observed by eye. Moreover, the diodes were of the same type and taken from the same box.
Now about the design of the light emitter. Perhaps this is the most interesting detail. As you can see in the photos, the LEDs in the circuit are not soldered tightly, but are a removable part of the structure. I decided to do this in order not to smoke the flashlight, and on occasion it would be possible to insert an ordinary light bulb into it. As a result of long deliberations on the subject of killing two birds with one stone, the following design was born:
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I think that special explanations are not required here. The native bulb is gutted from the same flashlight, 4 cuts are made in the flange from 4 sides (one was already there). 4 LEDs are arranged symmetrically in a circle with some spread for a larger angle of coverage (I had to file them a little at the base). The positive leads (as it happened according to the scheme) are soldered to the base near the cuts, and the negative leads are inserted from the inside into the central hole of the base, cut off and also soldered. The result is such a "lamp diode" that takes the place of a conventional incandescent bulb.
And finally, about the test results. For testing, half-dead batteries were taken in order to bring them to the finish line faster and understand what the newly made flashlight is capable of. The voltage of the batteries, the voltage at the load and the current through the load were measured. The run began with a battery voltage of 2.5V, at which the LEDs no longer light directly. The stabilization of the output voltage (3.3V) continued until the supply voltage decreased to ~1.2V. The load current in this case was about 100mA (~ 25mA per diode). Then the output voltage began to gradually decrease. The circuit has switched to a different mode of operation, in which it no longer stabilizes, but outputs everything it can. In this mode, it worked up to a supply voltage of 0.5V! The output voltage at the same time dropped to 2.7V, and the current from 100mA to 8mA. The diodes were still on, but their brightness was only enough to illuminate the keyhole in the dark entrance. After that, the batteries practically stopped discharging, because the circuit stopped consuming current. After running the circuit in this mode for another 10 minutes, I got bored and turned it off, because further running was of no interest.
The brightness of the glow was compared with a conventional incandescent bulb at the same power consumption. A 1V 0.068A bulb was inserted into the flashlight, which, at a voltage of 3.1V, consumed approximately the same current as the LEDs (about 100mA). The result in favor of LEDs is clear.
Part II. A little about efficiency or "There is no limit to perfection."
It's been over a month since I put together my first circuit to power an LED flashlight and wrote about it in the above article. To my surprise, the theme turned out to be very popular, judging by the number of reviews and visits to the site. Since then, I have gained some understanding of the subject :) and I felt it was my duty to take the subject more seriously and do more thorough research. I was also led to this idea by communication with people who solved similar problems. I want to talk about some new results.
First, I should have measured the efficiency of the circuit right away, which turned out to be suspiciously low (about 63% with fresh batteries). Secondly, I understood the main reason for such low efficiency. The fact is that those miniature chokes that I used in the circuit have an extremely high ohmic resistance - about 1.5 ohms. There was no question of any energy savings with such losses. Thirdly, I found that the value of the inductance and output capacitance also affect the efficiency, although not so noticeably.
Somehow I didn’t want to use a DM type choke because of its large size, so I decided to make a choke myself. The idea is simple - you need a low-turn choke, wound with a relatively thick wire, and at the same time quite compact. The ideal solution turned out to be a ring made of µ-permalloy with a permeability of about 50. There are ready-made chokes on such rings for sale, which are widely used in all kinds of switching power supplies. At my disposal was such a 10 μG choke, which has 15 turns on the K10x4x5 ring. Rewinding it was no problem. The inductance had to be selected by measuring the efficiency. In the range of 40-90mcg, the changes were very slight, less than 40 - more noticeable, and at 10mcg it became very bad. I did not raise it above 90 μG, because the ohmic resistance increased, and the thicker wire "inflated" the dimensions. As a result, more for aesthetic reasons, I settled on 40 turns of PEV-0.25 wire, because they lay down evenly in one layer and it turned out about 80 μG. The active resistance turned out to be about 0.2 ohm, and the saturation current, according to calculations, is more than 3A, which is enough for the eyes .. I replaced the output (and at the same time the input) electrolyte with 100 μF, although without compromising efficiency, it can be reduced to 47 μF. As a result, the design has undergone some changes, which, however, did not prevent it from maintaining its compactness:
Laboratory work" href="/text/category/laboratornie_raboti/" rel="bookmark">lab work and removed the main characteristics of the scheme:
| 1. The dependence of the output voltage, measured on the capacitance C3, on the input. I took this characteristic before and I can say that replacing the throttle with a better one gave a more horizontal shelf and a sharp break. |
| 2. It was also interesting to trace the change in the current consumed as the batteries are discharged. The "negativity" of the input resistance, typical for key stabilizers, is clearly visible. The peak of consumption fell on a point close to the reference voltage of the microcircuit. A further drop in voltage led to a decrease in the support, and hence the output voltage. The sharp drop in current consumption on the left side of the graph is caused by the non-linearity of the IV characteristics of the diodes. |
| 3. And finally, the promised efficiency. Here it was already measured by the final effect, i.e., by the power dissipated by the LEDs. (Percent 5 is lost on ballast resistance). Chip manufacturers did not lie - with the correct scheme, it gives the prescribed 87%. True, this is only with fresh batteries. As the current consumption increases, the efficiency naturally decreases. At the extreme point, it generally falls to the level of a locomotive. The increase in efficiency with a further decrease in voltage is of no practical value, since the flashlight is already "out of breath" and shines very weakly. |
Looking at all these characteristics, we can say that the flashlight shines confidently when the supply voltage drops to 1V without a noticeable decrease in brightness, i.e. the circuit actually works out a threefold voltage drop. An ordinary incandescent bulb with such a discharge of batteries is unlikely to be suitable for lighting.
If something remains unclear to someone - write. I will answer by letter, and / or I will supplement this article.
Vladimir Rashchenko, E-mail: rashenko (at) inp. nsk. su
May, 2003
Velofara - what's next?
So, first headlight built, tested and tested. What are the future promising directions of LED headlights? The first stage, probably, will be a further increase in capacity. I plan to build a 10-diode headlight with a switchable mode of operation 5 \ 10. Well, further quality improvement requires the use of complex microelectronic components. For example, it seems to me that it would be nice to get rid of quenching / equalizing resistors - after all, 30-40% of energy is lost on them. And I would like to have stabilization of the current through the LEDs, regardless of the discharge of the source. The best option would be to turn on the entire chain of LEDs in series with current stabilization. And in order not to increase the number of series batteries, this circuit also needs to increase the voltage from 3 or 4.5 V to 20-25 V. Such, so to speak, are the specifications for the development of an "ideal headlight".
It turned out that specialized ICs are produced specifically for solving such problems. Their area of application is the control of LCD backlight LEDs for mobile devices - laptops. cell phones, etc. Dima led me to this information gdt(at)*****- THANKS!
In particular, a line of ICs for various purposes for controlling LEDs is produced by Maxim (Maxim Integrated Products, Inc), on the website of which ( http://www.) found the article "Solutions for Driving White LEDs" (Apr 23, 2002). Some of these "solutions" are great for a bike light:
https://pandia.ru/text/78/440/images/image015_32.gif" width="391" height="331 src=">
Option 1. Chip MAX1848, control of a chain of 3 LEDs.
https://pandia.ru/text/78/440/images/image017_27.gif" width="477" height="342 src=">
Option 3: Another scheme for switching on feedback is possible - from a voltage divider.
https://pandia.ru/text/78/440/images/image019_21.gif" width="534" height="260 src=">
Option 5. Maximum power, multiple LED strings, MAX1698 chip
current mirror", chip MAX1916.
https://pandia.ru/text/78/440/images/image022_17.gif" width="464" height="184 src=">
Option 8. Chip MAX1759.
https://pandia.ru/text/78/440/images/image024_12.gif" width="496" height="194 src=">
Option 10. Chip MAX619 - perhaps. the simplest wiring diagram. Operability when the input voltage drops to 2 V. Load 50 mA at Uin.> 3 V.
https://pandia.ru/text/78/440/images/image026_15.gif" width="499" height="233 src=">
Option 12. ADP1110 chip - rumored to be more common than MAXs, works starting from Uin = 1.15 V ( !!! only one battery!) Uout. up to 12 V
https://pandia.ru/text/78/440/images/image028_15.gif" width="446" height="187 src=">
Option 14. The LTC1044 chip is a very simple connection scheme, Uin = 1.5 to 9 V; Uout = up to 9 V; load up to 200mA (but by the way, typical 60mA)
As you can see, it all looks very tempting :-) It remains only to find these chips somewhere inexpensively ....
Hooray! Found ADP1 rub. with VAT) We are building a new powerful headlight!
10 LEDs, 6/10 switching, five strings of two.
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MAX1848 White LED Step-Up Converter to SOT23
MAX1916 Low-Dropout, Constant-Current Triple White LED Bias Supply
Display Drivers and Display Power Application Notes and Tutorials
Charge Pump Versus Inductor Boost Converter for White LED Backlights
Buck/Boost Charge-Pump Regulator Powers White LEDs from a Wide 1.6V to 5.5V Input
Analog ICs for 3V Systems
From the Rainbow Tech website: Maxim: DC-DC converters(pivot table)
From the Premier Electric website: Switching regulators and controllers for IP without galv. interchanges(pivot table)
On the Averon website - chips for power supplies(Analog Devices) - pivot table
Powering LEDs with ZXSC300
The expediency of using LEDs in lamps, bicycle lights, in local and emergency lighting devices today is beyond doubt. The light output and power of LEDs is growing, and their prices are falling. There are more and more light sources in which white LEDs are used instead of the usual incandescent lamp and it is not difficult to buy them. Shops and markets are filled with Chinese-made LED products. But the quality of this product leaves much to be desired. Therefore, there is a need to modernize affordable (primarily at a price) LED light sources. Yes, and replacing incandescent lamps with LEDs in high-quality Soviet-made lanterns also makes sense. I hope that the information below will not be superfluous.
As you know, the LED has a nonlinear current-voltage characteristic with a characteristic "heel" in the initial section.
Rice. one Volt-ampere characteristic of a white LED. As we can see, the LED starts to glow if a voltage of more than 2.7 V is applied to it. When it is powered by a galvanic or rechargeable battery, the voltage of which gradually decreases during operation, the brightness of the radiation will vary widely. To avoid this, it is necessary to feed the LED with a stabilized current. And the current must be rated for this type of LED. Typically for standard 5mm LEDs it averages 20mA. For this reason, it is necessary to use electronic current stabilizers, which limit and stabilize the current flowing through the LED. It is often necessary to power the LED from one or two batteries with a voltage of 1.2 - 2.5 V. For this, step-up voltage converters are used. Since any LED is, in fact, a current device, it is advantageous from an energy efficiency point of view to provide direct control of the current flowing through it. This eliminates the losses that occur on the ballast (current-limiting) resistor. One of the best options for powering various LEDs from autonomous low-voltage current sources of 1-5 volts is the use of a specialized ZXSC300 microcircuit from ZETEX. ZXSC300 is a pulsed (inductive) DC-DC boost converter with pulse frequency modulation. Consider the principle of operation of the ZXSC300. On the image Fig.2 shows one of the typical circuits for powering a white LED with a pulsed current using the ZXSC300. The pulsed power supply mode of the LED allows the most efficient use of the energy available in the battery or accumulator.
In addition to the ZXSC300 chip itself, the converter contains: a 1.5 V battery, an L1 storage inductor, a power switch - a VT1 transistor, a current sensor - R1. The converter works in the traditional way for it. For some time, due to the pulse coming from the generator G (through the driver), the transistor VT1 is open and the current through the inductor L1 increases linearly. The process lasts until the moment when the voltage drop on the current sensor - low-resistance resistor R1 reaches a value of 19 mV. This voltage is sufficient to switch the comparator (the second input of which is supplied with a small exemplary voltage from the divider). The output voltage from the comparator is supplied to the generator, as a result of which the power switch VT1 closes and the energy stored in the inductor L1 enters the VD1 LED. Then the process is repeated. Thus, fixed portions of energy are supplied to the LED from the primary power source, which it converts into light. Energy management takes place using PFM Pulse Frequency Modulation (PFM). The principle of PFM is that the frequency changes, and the duration of the pulse or pause, respectively, of the open (On-Time) and closed (Off-Time) state of the key remains constant. In our case, the Off-Time remains unchanged, i.e., the duration of the pulse at which the external transistor VT1 is in the closed state. For the ZXSC300 controller, Toff is 1.7 µs. This time is enough to transfer the accumulated energy from the inductor to the LED. The duration of the pulse Ton, during which VT1 is open, is determined by the value of the current-sense resistor R1, the input voltage, and the difference between the input and output voltage, and the energy that accumulates in the inductor L1 will depend on its value. It is considered optimal when the total period T is 5 µs (Toff +Ton). The corresponding operating frequency is F=1/5µs=200 kHz. With the values of the elements indicated in the diagram in Fig. 2, the oscillogram of the voltage pulses on the LED has the form
Fig.3 type of voltage pulses on the LED. (grid 1V/div, 1µs/div) A little more about the parts used.Transistor VT1 - FMMT617, n-p-n transistor with a guaranteed collector-emitter saturation voltage of not more than 100 mV at a collector current of 1 A. Able to withstand a collector pulse current of up to 12 A (constant 3 A), collector-emitter voltage 18 V, coefficient current transmission 150...240. Transistor dynamic characteristics: on/off time 120/160 ns, f = 120 MHz, output capacitance 30 pF. FMMT617 is the best switching device that can be used with ZXSC300. It allows you to get high conversion efficiency at an input voltage of less than one volt.
Accumulative choke L1. As a storage choke, you can use both industrial SMD Power Inductors and homemade ones. Inductor L1 must withstand the maximum current of the power switch VT1 without saturation of the magnetic circuit. The active resistance of the inductor winding should not exceed 0.1 Ohm, otherwise the efficiency of the converter will noticeably decrease. As a core for self-winding, ring magnetic circuits (K10x4x5) from power filter chokes used in old computer motherboards are well suited. Today, used computer hardware can be purchased at bargain prices on any radio market. And "iron" is an inexhaustible source of various parts for radio amateurs. With self-winding, you will need an inductance meter for control. Current sense resistor R1. The low-resistance resistor R1 47mΩ is obtained by parallel connection of two SMD resistors of size 1206, 0.1Ω each. LED VD1. LED VD1 white glow with a rated operating current of 150 mA. The author's design uses two four-chip LEDs connected in parallel. The rated current of one of them is 100 mA, the other 60 mA. The operating current of the LED is determined by passing a stabilized DC current through it and controlling the temperature of the cathode (negative) terminal, which is a heat sink and removes heat from the crystal. At rated operating current, the temperature of the heat sink should not exceed degrees. Instead of one VD1 LED, you can also use eight standard 5 mm LEDs connected in parallel with a current of 20 mA. Appearance of the device
Shown in Fig. 5 Rice. 5(size 14 by 17 mm). When developing boards for such devices, it is necessary to strive for the minimum values of capacitance and inductance of the conductor connecting K VT1 with a storage choke and LED, as well as the minimum inductance and active resistance of the input and output circuits and the common wire. The resistance of the contacts and wires through which the supply voltage is supplied should also be minimal. In the following diagrams Fig. 6 and Fig. 7 shows how to power high-power Luxeon type LEDs with a rated operating current of 350 mA Rice. 6 How to power high-power Luxeon LEDs Rice. 7 The way to power high-power LEDs such as Luxeon - ZXSC300 is powered from the output voltage. In contrast to the previously discussed scheme, here the LED is powered not pulsed, but direct current. This allows you to easily control the operating current of the LED and the efficiency of the entire device. Feature of the transducer in Fig. 7 is that the ZXSC300 is powered by the output voltage. This allows the ZXSC300 to work (after startup) with a decrease in input voltage down to 0.5 V. Diode VD1 - Schottky rated for 2A current. Capacitors C1 and C3 are ceramic SMD, C2 and C3 are tantalum SMD. The number of LEDs connected in series. | Resistance of the current-measuring resistor, mOhm. | Storage choke inductance, μH. |
||||
To date, powerful 3-5 W LEDs from various manufacturers (both eminent and not very famous) have become available for use.
And in this case, the use of ZXSC300 makes it easy to solve the problem of efficient power supply of LEDs with an operating current of 1 A or more.
It is convenient to use an n-channel (operating from 3 V) Power MOSFET as a power switch in this circuit, you can also use an assembly of the FETKY MOSFET series (with a Schottky diode in one SO-8 package).
With the ZXSC300 and some LEDs, it's easy to breathe new life into an old flashlight. The battery flashlight FAR-3 was upgraded.
Fig.11
LEDs were used 4-crystal with a rated current of 100 mA - 6 pcs. Connected in series by 3. To control the luminous flux, two converters on the ZXSC300 are used, which have independent on / off. Each converter works on its own trio of LEDs.
Fig.12
The converter boards are made on double-sided fiberglass, the second side is connected to the power supply minus.
Fig.13
Fig.14
The flashlight FAR-3 uses three sealed batteries NKGK-11D (KCSL 11) as batteries. The nominal voltage of this battery is 3.6V. The final voltage of a discharged battery is 3V (1V per cell). Further discharge is undesirable as this results in a shortened battery life. And further discharge is possible - the converters on the ZXSC300 work, as we remember, up to 0.9 V.
Therefore, to control the voltage on the battery, a device was designed, the circuit of which is shown in Fig. fifteen.
Fig.15
This device uses an inexpensive accessible element base. DA1 - LM393 is a well-known dual comparator. The reference voltage of 2.5 V is obtained using TL431 (similar to KR142EN19). The response voltage of the DA1.1 comparator is about 3 V, set by the divider R2 - R3 (for accurate operation, it may be necessary to select these elements). When the voltage on the GB1 battery drops to 3 V, the red LED HL1 lights up, if the voltage is greater than 3 V, then HL1 goes out and the green LED HL2 lights up. Resistor R4 determines the hysteresis of the comparator.
The printed circuit board of the control device is shown in Rice. 16 ( size 34 by 20 mm).
If you have any difficulties in purchasing the ZXSC300 chip, FMMT617 transistor or low-resistance 0.1 Ohm SMD resistors, you can contact the author by e-mail david_ukr (аt) *****
You can purchase the following items (mail delivery)
Elements | Quantity | Price, $ | Price, UAH |
|
Chip ZXSC 300 + transistor FMMT 617 | ||||
Resistor 0.1 ohm SMD size 0805 | ||||
PCB Fig. eight |
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We make a flashlight on LEDs with our own hands
In the life of every person there are moments when you need lighting, but there is no electricity. This may be a banal power outage, and the need to repair the wiring in the house, and possibly a forest hike or something like that.
And, of course, everyone knows that in this case only an electric flashlight will help out - a compact and at the same time functional device. Now there are many different types of this product on the electrical engineering market. These are ordinary flashlights with incandescent lamps, and LED, with batteries and batteries. And there are a great many companies producing these devices - Dick, Lux, Cosmos, etc.
But what is the principle of its work, not many people think. Meanwhile, knowing the device and circuit of an electric flashlight, you can, if necessary, repair it or even assemble it with your own hands. This is the issue we will try to figure out.
The simplest lanterns
Since flashlights are different, it makes sense to start with the simplest - with a battery and an incandescent lamp, and also consider its possible malfunctions. The scheme of such a device is elementary.
In fact, there is nothing in it except a battery, a power button and a light bulb. And therefore there are no special problems with him. Here are a few possible minor annoyances that can lead to the failure of such a flashlight:
- Oxidation of any of the contacts. It can be the contacts of a switch, a light bulb or a battery. You just need to clean these circuit elements, and the device will work again.
- Incandescent lamp burning - everything is simple here, replacing the light element will solve this problem.
- Complete discharge of batteries - replacement of batteries with new ones (or charging, if they are rechargeable).
- No contact or broken wire. If the flashlight is no longer new, then it makes sense to change all the wires. It's not at all difficult to do this.
LED flashlight
This type of flashlight has a more powerful luminous flux and at the same time consumes very little energy, which means that the batteries in it will last longer. It's all about the design of light elements - LEDs do not have an incandescent filament, they do not consume energy for heating, in view of this, the efficiency of such devices is 80-85% higher. The role of additional equipment in the form of a converter with the participation of a transistor, a resistor and a high-frequency transformer is also great.
If the flashlight has a built-in battery, then a charger must be included with it.
The circuit of such a lamp consists of one or more LEDs, a voltage converter, a switch and a battery. In earlier models of flashlights, the amount of energy consumed by the LEDs had to match that produced by the source.
Now this problem is solved with the help of a voltage converter (it is also called a multiplier). Actually, it is he who is the main part that contains the electrical circuit of the flashlight.
If you want to make such a device with your own hands, there will be no particular difficulties. Transistor, resistor and diodes are not a problem. The most difficult moment will be winding a high-frequency transformer on a ferrite ring, which is called a blocking generator.
But even this can be dealt with by taking a similar ring from a faulty electronic ballast of an energy-saving lamp. Although, of course, if you don’t want to mess around or don’t have time, then you can find highly efficient converters such as 8115 on sale. With their help, using a transistor and a resistor, it became possible to manufacture an LED flashlight on a single battery.
The very scheme of the LED flashlight is similar to the simplest device, and you should not dwell on it, because even a child is able to assemble it.
By the way, when used in a voltage converter circuit on an old, simplest flashlight powered by a 4.5 volt square battery, which you can’t buy now, you can safely put a 1.5 volt battery, i.e. the usual “finger” or “little finger” battery. There will be no loss in light output. The main task in this case is to have at least the slightest idea of \u200b\u200bradio engineering, literally at the level of knowledge of what a transistor is, and also be able to hold a soldering iron in your hands.
Refinement of Chinese lanterns
Sometimes it happens that a purchased (seemingly quite high-quality) flashlight with a battery completely fails. And it is not at all necessary that the buyer is to blame for improper operation, although this also occurs. More often - this is a mistake when assembling a Chinese lantern in pursuit of quantity at the expense of quality.
Of course, in this case, it will have to be redone, somehow modernized, because money has been spent. Now you need to understand how to do this and whether it is possible to compete with a Chinese manufacturer and repair such a device yourself.
Considering the most common option, in which when the device is turned on, the charging indicator lights up, but the flashlight does not charge and does not work, you can see this.
A common manufacturer's mistake is that the charge indicator (LED) is connected to the circuit in parallel with the battery, which should not be allowed. At the same time, the buyer turns on the flashlight, and seeing that it is not lit, re-energizes the charge. As a result, all the LEDs burn out at once.
The fact is that not all manufacturers indicate that it is impossible to charge such devices with the LEDs on, because it will be impossible to repair them, all that remains is to replace them.
So, the task of upgrading is to connect the charge indicator in series with the battery.
As can be seen from the diagram, this problem is completely solvable.
But if the Chinese put a resistor 0118 in their product, then the LEDs will have to be changed constantly, because the current supplied to them will be very high, and no matter what light elements are installed, they cannot withstand the load.
LED headlamp
In recent years, such a light device has become quite widespread. Indeed, it is very convenient when the hands are free, and the beam of light hits where the person is looking, this is precisely the main advantage of the headlamp. Previously, only miners could boast of such, and even then, to wear it, a helmet was needed, on which the lantern, in fact, was attached.
Now the fastening of such a device is convenient, you can wear it under any circumstances, and a rather voluminous and heavy battery does not hang on your belt, which, moreover, must also be charged once a day. The modern one is much smaller and lighter, moreover, it has a very low power consumption.
So what is such a lamp? And the principle of its operation is no different from the LED. The options are the same - rechargeable or with removable batteries. The number of LEDs varies from 3 to 24 depending on the characteristics of the battery and converter.
In addition, such lights usually have 4 glow modes, and not just one. These are weak, medium, strong and signal - when the LEDs blink at short intervals.
The modes of the headlamp LED flashlight are controlled by a microcontroller. Moreover, if it is available, even a strobe mode is possible. In addition, this does not harm LEDs at all, unlike incandescent lamps, since their service life does not depend on the number of on-off cycles due to the absence of an incandescent filament.
So which flashlight should you choose?
Of course, flashlights can be different in terms of voltage consumption (from 1.5 to 12 V), and with different switches (touch or mechanical), with an audible warning about low battery. It can be the original or its analogues. And it is not always possible to determine what kind of device is in front of your eyes. After all, until it fails and its repair begins, it is impossible to see what microcircuit or transistor is in it. It is probably better to choose the one you like, and solve possible problems as they come.
Once upon a time, they gave me such a Chinese lantern
After six months of use, it stopped working. I open the case to determine the cause of the failure.
Forgot to turn off the flashlight after use. Due to the absence of any protection circuits, lead batteries were discharged to zero. Apparently there was a sulfation of the plates, and when charging, the batteries practically did not consume current. Then the mains voltage from transformerless charging, through the included toggle switch, rushed to the LEDs. As a result, all 15 LEDs failed, and only the case remained in working order.
Looking at the insides of this Chinese lantern, I will immediately note its main shortcomings:
- no protection against deep discharge of the battery (discharges to zero)
- no control of the battery charging process (charges indefinitely)
- no low battery indication
- Terrible retractable power plug design
I decided to repair the flashlight by doing a complete upgrade with the replacement of all the insides. So what would you like to end up with:
- powered by a lithium-ion battery (to lighten the weight)
- battery charging through a specialized controller (with indication and automatic shutdown)
- turning on / off the flashlight with a tact button
- indication of the fast discharge of the battery (voltage 3.7V)
- shutdown when the battery is completely discharged (voltage 3.6V)
- USB charging capability
- automatic shutdown of the flashlight when charging
- design without the use of rare, expensive components and microcontrollers
No sooner said than done. Control block diagram.
I will briefly describe the main nodes of the circuit:
- Components DA4, VT3, R17, R24, C16 form a secondary battery discharge protection unit. This node disconnects the load from the battery when the voltage drops to 2.5 volts. The secondary protection unit can be omitted; this will require the installation of jumper R12.
- Components DA3, R16, R18, R21, HL2, HL3, C9, C13 form a battery charging unit with automatic shutdown, current control, and indication of the charging process.
- Components DD1, C11, R19, VD1 form the trigger needed to control the flashlight with a tact button.
- On components C12, R20, R22, a circuit is assembled to suppress the bounce of the contacts of the SB1 button.
- Circuit R15, VD3 resets the trigger when the flashlight is charging.
- Components VT1, VT2, R13, R14 organize the power supply to the circuit and LEDs.
- Components DA1, C1, C3, R5, R6, R7, C4, C5 form a 1.25 volt reference voltage source.
- Components DA2, HL1, C2, R2, R3, R4, R8 form a low battery indication unit.
- Components DA2, R9, R10, C8, VD2 form a primary protection unit against battery discharge.
- Resistors R1, R11, R23 act as fuses.
Let's move on to iron. To begin with, I will be engaged in the restoration of the LED block. I open the reflector.
Removing burned out LEDs.
I solder serviceable LEDs taken from an old faulty flashlight. I also change all resistors to a nominal value of 100 ohms.
The LED block has been restored. Block diagram.
Now I'm going to make the control board. To do this, I remove all dimensions and print an impromptu board on the printer.
I breed a printed circuit board, make it using LUT technology, and solder the components.
On the left, you can see that the secondary protection unit against battery discharge is not soldered to the board, jumper R12 is installed instead.
Now you need to turn the switch into a tact button. I disassemble the switch.
I cover the regular cutout with a piece of black plastic.
I drill holes.
I fix a small scarf with a clock button.
The button is ready.
Initially, the flashlight was equipped with a single indicator that lights up when plugged into the network. In fact, this indicator was absolutely useless. The upgraded board contains three indicators - red, green, yellow.
It is necessary to drill holes for the light guides in the plastic insert.
I removed the light guides from an old CRT monitor.
Upgraded plastic insert with light guides.
I install the board with the battery in the flashlight housing. The battery is attached to the board with double-sided tape.
Inside the case, the board feels like home.
I return the plastic inserts to their place.
I'm assembling the body.
The flashlight has become reliable and convenient. Using them is a pleasure.
A red indicator means that the battery is almost empty and the flashlight will turn off soon.
When charging, the yellow indicator lights up.
At the end of the charging process, the green indicator lights up.
Finally, I suggest watching a short video.
List of radio elements
| Designation | Type of | Denomination | Quantity | Note | Score | My notepad |
|---|---|---|---|---|---|---|
| R1, R11, R23 | Resistor | 0 ohm | 3 | 1206 | To notepad | |
| R2 | Resistor | 10 kOhm | 1 | 0805 | To notepad | |
| R3 | Resistor | 1 MΩ | 1 | 0805 | To notepad | |
| R4 | Resistor | 5.1 kOhm | 1 | 0805 | To notepad | |
| R5, R18, R21 | Resistor | 300 ohm | 3 | 0805 | To notepad | |
| R8 | Resistor | 300 ohm | 1 | 1206 | To notepad | |
| R6, R7, R15 | Resistor | 100 kOhm | 3 | 1206 | To notepad | |
| R13, R19 | Resistor | 100 kOhm | 2 | 0805 | To notepad | |
| R9 | Resistor | 6.8 kOhm | 1 | 1206 | To notepad | |
| R10 | Resistor | 3.6 kOhm | 1 | 0805 | To notepad | |
| R14 | Resistor | 330 ohm | 1 | 1206 | To notepad | |
| R16 | Resistor | 3 kOhm | 1 | 0805 | To notepad | |
| R17 | Resistor | 1 kOhm | 1 | 0805 | To notepad | |
| R22 | Resistor | 1 kOhm | 1 | 1206 | To notepad | |
| R20 | Resistor | 20 kOhm | 1 | 0805 | To notepad | |
| R24 | Resistor | 100 ohm | 1 | 0805 | To notepad | |
| C1, C3, C9, C13 | Capacitor | 10uF 10V | 4 | 1206 | To notepad | |
| C2, C4, C6, C8, C11, C15, C16 | Capacitor | 100nF 10V | 7 | 0805 | To notepad | |
| C5, C7, C10, C12 | Capacitor | 1uF 10V | 4 | 0805 | To notepad | |
| C14 | Tantalum capacitor | 47uF 10V | 1 | D | To notepad | |
| DA1 | Linear Regulator | AMS1117-ADJ | 1 | SOT-223 | To notepad | |
| DA2 | Operational amplifier | LM358 | 1 | SOIC-8 | To notepad | |
| DA3 | charge controller | TP4056 | 1 | SOIC-8EP | To notepad | |
| DA4 | Protection Controller | DW01p | 1 | SOT-23-6 | To notepad | |
| DD1 | Decimal counter | HEF4017 | 1 | SOIC-16 | To notepad | |
| VT1 | MOSFET transistor |
The wide use of LEDs is hampered by their technical characteristics, in particular, the nonlinear current-voltage characteristic and "uncomfortable" supply voltages. Therefore, for LEDs, various kinds of voltage converters are used, operating on the basis of transformers or inductive energy storage devices. The proposed design of the LED flashlight is powered by two AA batteries, as a light-emitting device, a super-bright snow-white LED DFL-OSPW5111P with a brightness of 30 cd was used with a current consumption of only 80 mA
The flashlight circuit is quite simple, because it does not contain microcontrollers, does not require configuration, and should start working immediately after assembly and power supply. The algorithm of work is the following. When the battery G1 is connected, the C6R8 circuit resets the counter DD1. Button SB1 is connected to the counting input DD1 through the circuit C8-R11-R12 (anti-bounce). By pressing SB1, we cause DD1 to operate, a logical unit is set at the OUT1 pin, the DA2 LED driver turns on, its output current is about 350 mA. When you click on SB1 again, on OUT2 "log. 1", and through VD3 the counter is reset, the DA2 driver is turned off. A classic charger is built on DA1, with the resistance R1 we select the desired charging current. In this design, the current is limited to 500 mA. When charging, the counter DD1 is reset through R10-VD4. That is, the operation of the device is temporarily blocked while the battery is being charged. The DA3 microassembly and the VT1 FS8205 transistor form a lithium-ion battery discharge protection circuit. Power to DA3 follows through VD1 and VD2. This is necessary to raise the level of protection operation to 3 volts.
The printed circuit board of the flashlight and the stages of its assembly in the photos can be downloaded from the link above:
This design allows you to connect from three to ten ultra-bright LEDs with a current of up to 750 mA.
Remember that the board supply voltage must not be higher than the supply voltage of the LEDs used. To reduce power consumption and increase efficiency, n-channel has been added to the design, which has a very low resistance. To control the power transistor, the circuit has a control unit based on a bipolar transistor, resistor R1 and diode VD1.
At the moment the control signal appears, the bipolar transistor is closed, and the MOSFET gate is charged through the VD1 diode. At the end of the pulse, the gate VT2 will be discharged through the open transistor. This mode of operation guarantees the instantaneous opening and closing of the MOSFET, and thereby increases the efficiency of the converter.
The design is based on the LMC555 chip. In this case, it works as a square wave generator. Unlike the scheme of its standard use, in this case, a BAT85 Schottky diode was added to the flashlight circuit. Thanks to its use, two different time periods can be adjusted independently of each other. The length of time at which the output will be logic high is set by the resistance R1 and capacitance C2, and the length of time at which the output will be logic low depends on the resistor R2, potentiometer P1 and capacitor C2. The fill factor can be changed from 30% to 96%. Thus, dimming is carried out, that is, a change in the brightness of the glow of three powerful light sources that provide illumination. The LMC555 circuit is a CMOS version of the popular and well-known LM555 timer in the amateur radio community, but it consumes much less current, so it is advisable to use its name. An additional driver on a field-effect transistor BS170 (T1) is used to control the load at the output of the flashlight circuit. This field worker can operate with a load current of up to 500 mA. Below is a diagram of a mini USB flashlight.
The backlight is connected to a mobile phone or tablet using the Mini USB interface. In practice, however, it turned out that not all digital gadgets can deliver 500 mA, and this must be taken into account when connecting a flashlight to the device.
A distinctive feature of the proposed amateur radio design is that a stepper motor from a floppy disk drive is used as a power source. Generating a flow of free electrons due to the pendulum motion of the rotor. Therefore, they are quite comfortable to use. The voltage on the LEDs depends only on the intensity of rotation of the armature of the stepper motor.
Properly made lighting of a park or summer cottage can turn a lifeless dull space into a fantastic fairy tale. The garden LED lamp, the scheme of which is discussed below, is used to organize landscape gardening and lighting. At the same time, the lamps perform a dual function: they are a source of artificial lighting and decorative items for your garden.
Making an LED lamp with your own hands is quite simple, a little free time, some components for the circuit and your desire. The best option for a novice radio amateur is the alteration of an existing lamp
Many who bought an inexpensive Chinese flashlight with a super-bright LED complain that the batteries in them die very quickly. In fact, this is indeed the case, because, as a rule, they do not have a charge and discharge controller, but.
The scheme, firmware, project in Proteus and the program can be downloaded from the cloud from the link above.
DIY simple LED flashlight |
With this decision, it turned out to reduce the dimensions of the entire system, first of all, the magnetic circuit of the converter transformer.
Transformer T1 is wound on a K10x6x3 ring magnetic core made of 2000NM ferrite. The primary and secondary windings of the transformer are wound immediately (i.e., in 4 wires).
After winding the transformer, the winding leads are connected according to the scheme. Resistor R1 - MLT, KT529A transistors, can be replaced by KT530A, but it is necessary to change the polarity on the batteries.
The LED is placed in the body of the flashlight instead of an incandescent lamp, but so that it protrudes 0.5 ... 1 mm from the socket for its installation.
The main advantage of this scheme is low power consumption and the presence of a signal mode due to the rhythmic blinking of the LEDs. which can be adjusted over a wide range.
Despite the low supply voltage of only 7-15V, the LED spotlight gives brightness no worse than the brightness of car headlights. The schematic diagram of the spotlight is made on a DC-DC converter on a D2 LM2575-5V chip.
, (see reference data) supports 5V stabilized voltage. They are powered by a battery of 22 LEDs. The LEDs are connected in pairs in series, 4.2V drops on each pair. The remaining 0.8V is quenched by resistors R3-R13. Pumping occurs on the inductance L1, the diode VD1 serves as a rectifier, and the capacitor C5 works as an integrator.
The LM2575 chip has a blocking mode at pin 5. When a logical unit is applied to it, the LM2575 chip turns off and the spotlight goes out. If the toggle switch S1 is thrown in the “Blink” position, then pulses from the multivibrator on the D1 K561LE5 chip will arrive at pin 5 D2, the frequency of which can be adjusted by the variable resistor R2. Choke L1 is wound on a ferrite ring 2000NM with a diameter of 23mm. It contains 60 turns of PEV 0.61 wire.
You can use almost any super-bright or super-bright LEDs, but with a drop voltage of no more than 2.4V. High voltage drop LEDs can also be used, but they need to be turned on one at a time.
This LED flashlight circuit provides an automatic shutdown function that protects the battery from deep discharge, which is very important for Ni-MH or Ni-Cd batteries of AA, AAA size, and for tourism and camping, this size is key, because instead of it you can use the usual most common batteries in Russia. The power in this circuit is calculated from seven AA batteries, so we used a step-down voltage converter to power the LEDs.