How to repair an LED flashlight? Diagram of a Chinese lantern with mains charging

Repair of LED lights - overview of breakdowns, device and diagram

For normal human life in the dark, he always needed light. With the development of technology, lighting sources have improved, starting from the fire of torches and kerosene lamps, ending with battery-powered flashlights. A real revolution in the world of lighting technology was the creation of the LED, which immediately entered everyday life.

Modern LED lights are very economical, the light spreads very far and is very bright. A huge share of such lithium flashlights on the modern market are made in China; they are very cheap and affordable. It is because of the cheapness that various types of breakdowns often occur. In this article, we will look at the main problems of repairing LED lights and how to fix them yourself.

How does an LED flashlight work?

The classic design of flashlights is very simple (regardless of the type of housing, be it the Cosmos or DiK AN-005 models). An LED is connected to the battery, the circuit is broken by the shutdown button. Depending on the number of LEDs, the number of light elements themselves (for example, the main light on the front and an auxiliary one in the handle), a stronger battery (or several), a transformer, a resistance are added to the circuit, and a more functional switch is installed (Fo-DiK flashlights) .

Why do flashlights break?

Now we will omit the problems associated with improper operation of the Chinese lantern - “I dropped it in a bowl of water, turned it on and off, but for some reason it does not shine.” The cheapness of flashlights is achieved by simplifying the electrical circuits inside the device. This allows you to save on components (their quantity and quality). This is done so that people buy new ones more often, and simply throw away the old ones without even trying to fix them with their own hands.

Another point of savings is people working in production who do not have sufficient qualifications to perform such work. As a result, there are many small and large errors in the circuit itself, poor-quality soldering and assembly of components, which leads to constant repair of the lamps. In most cases, all problems can be solved by diagnosing them correctly, which is what we will do next.

Cause of flashlight failure

Most likely, when the switch is switched, the LEDs do not want to light up due to a malfunction in the electrical circuit. The most common of them:

• oxidation of battery or battery contacts;
• oxidation on the contacts to which the battery is connected;
• damage to the wires going both from the battery to the LED and back;
• faulty shutdown element;
• lack of power in the circuit;
• failure in the LEDs themselves.

Oxidation. Most often it occurs in already old lanterns, which are often used in various weather conditions. The deposit that appears on the metal interferes with normal contact, which is why the battery-powered flashlight may flicker or not turn on at all. If oxidation is observed on the battery or accumulator, then you need to think about replacement.

How to fix contacts? Light stains can be removed with your own hands using a cotton swab dipped in ethyl alcohol. When the contamination is very serious, even rust has spread to the body - using such a battery can be dangerous to health and life. In stores you can now find a sufficient number of new batteries and accumulators, even for old types of flashlights.

Take care of the environment - do not throw old batteries in the trash, you probably have recycling collection points in your city.

Oxidation also forms on the contacts in the flashlight itself. Here, too, you need to pay attention to their integrity. If the dirt can still be removed with a cotton swab and alcohol, go with this option. For hard-to-reach places, you can use a cotton swab.

If the contacts are completely rusty or even rotten (which is not uncommon for an old flashlight), they will have to be replaced. Ask your electronics store if there are similar contact elements (for at least ten years, they have been absolutely identical in all flashlights with rare exceptions). If there are no similar ones, choose as similar an option as possible. Armed with a thin soldering iron, you can easily re-solder them.

Damage to wire contacts. In addition to the places described above, contacts are present at the places where the wires of the electrical circuit are soldered. Cheap production, haste during assembly and careless attitude of workers often lead to the fact that some wires are completely forgotten to be soldered, so the LED flashlight does not work, even if it is just out of the box. How to repair the flashlight in this case? Carefully examine the entire circuit, carefully moving the wires away with medical tweezers or another thin object. If a failed soldering is found, it must be restored using the same thin soldering iron.

The same can be done with flimsy connections, the characteristic condition of which is a torn bare core, barely attached to the joint. If you have enough time and resources, and you value this flashlight, you can methodically and efficiently re-solder all the contacts. This will significantly increase the efficiency of such a circuit, protect exposed elements from moisture and dust (which is important if the flashlight is a headlamp), and in subsequent cases of repairing the flashlight, this item will be eliminated. Repairing small LED headlamps is done exactly the same, the sizes are just different.

Damage to wires. Once you have ensured that the contacts are clean, you can begin to inspect all the wires in the circuit for damage or shorts. A common case is when, either during assembly at the factory or after a previous repair, the wiring was damaged by an incorrectly installed housing cover. The wire got caught between two housing parts and was cut or crushed while tightening the bolts. During the flow of current, the electrical circuit could overheat or even short out, this will inevitably lead to repair of the LED flashlight.

All torn sections must be soldered together to ensure better conductivity than with simple twisting. Do not forget to insulate all bare areas; it is best to use thin heat shrink. It is advisable to completely replace severely damaged wires, which may have already become rusty, with your own hands (select the appropriate wire). After such modifications, old lights can shine much brighter - the modernization improves the flow of current.

Faulty switch. Also pay attention to the contacts of the wires with the switch terminals and troubleshoot. The easiest way to find out if the switch is causing your flashlight to not work is to complete the circuit without it. Eliminate it from the circuit by directly connecting the battery to the LEDs (you can also try from the mains with a voltage corresponding to the battery). If they light up, change the switch. Perhaps it has already mechanically broken down from repeated use, the flashlight just turns off, or there may also be a manufacturing defect. If the LEDs do not want to light up directly from the battery, we proceed further.

Lack of current in the network. The most common cause of such a malfunction is a discharged or very old lithium battery. The LED flashlight can glow when charging, but if it is unplugged from the outlet, it immediately goes out. A complete malfunction is observed when the flashlight does not charge at all and does not react in any way when turned on, although the charging indicator lights up steadily.

LED failure. Once all the problems with the wires are fixed (or there were none), turn your attention to the LEDs themselves. Carefully remove the board on which they are soldered. Use a multimeter to find out the current going into and out of the board. If possible, check the contacts on the entire board. Most likely, the LEDs are connected in series, so if one breaks, the others will not light either. Checking each one, if there are 3 or more of them, takes quite a long time, so it is better to immediately buy new LEDs.

Board with LEDs

Conclusion

Many cheap Chinese LED flashlights, assembled under conditions of austerity, are most often susceptible to electrical circuit failures. Wires with a very small cross-section are installed there, which are quite problematic to solder even with a good device. However, almost all problems with wires and batteries can be easily fixed at home; with the right and careful approach, even an inexpensive repaired flashlight will last you more than three years of constant use.

lampagid.ru

How to fix an LED Chinese flashlight yourself. DIY instructions for repairing LED lights with visual photos and videos

Today we will talk about how to fix an LED Chinese flashlight yourself. We will also consider instructions for repairing LED lights with your own hands with visual photos and videos

As you can see, the scheme is simple. Main elements: current-limiting capacitor, rectifier diode bridge with four diodes, battery, switch, super-bright LEDs, LED to indicate flashlight battery charging.

Well, now, in order, about the purpose of all the elements in the flashlight.

Current limiting capacitor. It is designed to limit the battery charging current. Its capacity for each type of flashlight may be different. A non-polar mica capacitor is used. The operating voltage must be at least 250 volts. In the circuit it must be bypassed, as shown, with a resistor. It serves to discharge the capacitor after you remove the flashlight from the charging outlet. Otherwise, you may get an electric shock if you accidentally touch the 220 volt power terminals of the flashlight. The resistance of this resistor must be at least 500 kOhm.

The rectifier bridge is assembled on silicon diodes with a reverse voltage of at least 300 volts.

To indicate the charging of the flashlight battery, a simple red or green LED is used. It is connected in parallel to one of the diodes of the rectifier bridge. True, in the diagram I forgot to indicate the resistor connected in series with this LED.

It makes no sense to talk about the other elements; everything should be clear anyway.

I would like to draw your attention to the main points of repairing an LED flashlight. Let's look at the main faults and how to fix them.

1. The flashlight stopped shining. There aren't many options here. The reason may be the failure of super-bright LEDs. This can happen, for example, in the following case. You put the flashlight on charge and accidentally turned on the switch. In this case, a sharp jump in current will occur and one or more diodes of the rectifier bridge may be broken. And behind them, the capacitor may not be able to withstand it and will short out. The voltage on the battery will increase sharply and the LEDs will fail. So, under no circumstances turn on the flashlight while charging unless you want to throw it away.

2. The flashlight does not turn on. Well, here you need to check the switch.

3. The flashlight discharges very quickly. If your flashlight is “experienced”, then most likely the battery has reached its service life. If you actively use the flashlight, then after one year of use the battery will no longer last.

Problem 1: The LED flashlight does not turn on or flickers when working

As a rule, this is the cause of poor contact. The easiest treatment is to tighten all the threads tightly. If the flashlight does not work at all, start by checking the battery. It may be discharged or damaged.

Unscrew the back cover of the flashlight and use a screwdriver to connect the housing to the negative terminal of the battery. If the flashlight lights up, then the problem is in the module with the button.

90% of the buttons of all LED flashlights are made according to the same scheme: The button body is made of aluminum with a thread, a rubber cap is inserted there, then the button module itself and a pressure ring for contact with the body.

The problem is most often solved by a loose clamping ring. To fix this problem, just find round pliers with thin tips or thin scissors that need to be inserted into the holes, as in the photo, and turned clockwise.

If the ring moves, the problem is fixed. If the ring stays in place, then the problem lies in the contact of the button module with the body. Unscrew the clamping ring counterclockwise and pull the button module out. Poor contact is often due to oxidation of the aluminum surface of the ring or the border on the printed circuit board (indicated by arrows)

Simply wipe these surfaces with alcohol and functionality will be restored.

Button modules are different. Some have contact through the printed circuit board, others have contact through the side petals to the flashlight body. Just bend the petal to the side so that the contact is tighter. Alternatively, you can make a solder from tin so that the surface is thicker and the contact is pressed better. All LED lights are basically the same

The plus goes through the positive contact of the battery to the center of the LED module. The minus goes through the body and is closed by a button.

It would be a good idea to check the tightness of the LED module inside the housing. This is also a common problem with LED lights.

Using round nose pliers or pliers, rotate the module clockwise until it stops. Be careful, it is easy to damage the LED at this point.

These actions should be quite enough to restore the functionality of the LED flashlight.

It’s worse when the flashlight works and the modes are switched, but the beam is very dim, or the flashlight doesn’t work at all and there’s a burning smell inside.

Problem 2. The flashlight works fine, but is dim or does not work at all and there is a burning smell inside

Most likely the driver has failed. The driver is an electronic circuit on transistors that controls the flashlight modes and is also responsible for a constant voltage level, regardless of the battery discharge.

You need to unsolder the burnt driver and solder in a new driver, or connect the LED directly to the battery. In this case, you lose all modes and are left only with the maximum one.

Sometimes (much less often) an LED fails. You can check this very simply. Apply a voltage of 4.2 V/ to the contact pads of the LED. The main thing is not to confuse the polarity. If the LED lights up brightly, then the driver has failed, if vice versa, then you need to order a new LED.

Unscrew the module with the LED from the housing. Modules vary, but as a rule, they are made of copper or brass and

The weakest point of such flashlights is the button. Its contacts oxidize, as a result of which the flashlight begins to shine dimly, and then may stop turning on altogether. The first sign is that a flashlight with a normal battery shines weakly, but if you click the button several times, the brightness increases.

The easiest way to make such a lantern shine is to do the following:

1. Take a thin stranded wire and cut off one strand.2. We wind the wires onto the spring.3. We bend the wire so that the battery does not break it. The wire should protrude slightly above the twist part of the flashlight.4. Twist tightly. We break off (tear off) the excess wire. As a result, the wire ensures good contact with the negative part of the battery and the flashlight will shine with the proper brightness. Of course, with such repairs the button is no longer available, so turning the flashlight on and off is done by turning the head part. My Chinese guy worked like this for a couple of months. If you need to change the battery, do not touch the back of the flashlight. We turn our heads away.

Today I decided to bring the button back to life. The button is located in a plastic case, which is simply pressed into the back of the flashlight. In principle, it can be pushed back, but I did it a little differently:

1. Use a 2 mm drill to make a couple of holes to a depth of 2-3 mm.2. Now you can use tweezers to unscrew the housing with the button.3. Remove the button.4. The button is assembled without glue or latches, so it can be easily disassembled with a stationery knife. The photo shows that the moving contact has oxidized (a round thing in the center that looks like a button). It can be cleaned with an eraser or fine sandpaper and put the button back together, but I decided to tin it additionally both this part and the fixed contacts.

1. Clean with fine sandpaper.2. Apply a thin layer to the areas marked in red. We wipe off the flux with alcohol and assemble the button.3. To increase reliability, I soldered a spring to the bottom contact of the button.4. We put everything back together. After the repair, the button works perfectly. Of course, tin also oxidizes, but since tin is a fairly soft metal, I hope that the oxide film will be easily destroyed when the button is used. It’s not for nothing that the central contact on light bulbs is made of tin.

IMPROVING FOCUS.

My Chinese guy had a very vague idea of ​​what a “hotspot” was, so I decided to enlighten him. We unscrew the head part.

1. There is a small hole in the board (arrow). Using an awl, unscrew the filling while lightly pressing your finger on the outside of the glass. This makes it easier to unscrew.2. Remove the reflector.3. We take ordinary office paper, punch 6-8 holes with an office hole punch. The diameter of the hole punch holes perfectly matches the diameter of the LED. Cut out 6-8 paper washers.4. Place the washers on the LED and press them with the reflector. Here you will have to experiment with the number of washers. I improved the focusing of a couple of flashlights in this way; the number of washers was in the range of 4-6. The current patient required 6 of them.

The Chinese save on everything. A couple of extra details will increase the cost, so they don’t install it.

The main part of the diagram (marked in green) may be different. On one or two transistors or on a specialized microcircuit (I have a circuit of two parts: a choke and a microcircuit with 3 legs, similar to a transistor). But they save money on the part marked in red. I added a capacitor and a pair of 1n4148 diodes in parallel (I didn't have any shots). The brightness of the LED increased by 10-15 percent.

remontavto-moto-velo.blogspot.com

Improved LED flashlight - RadioRadar

Lighting engineering

Home For amateur radio Lighting equipment

At night, a pocket flashlight is an indispensable thing. However, the commercially available samples with a rechargeable battery and charging from the mains are only disappointing. They still work for some time after purchase, but then the gel lead-acid battery degrades and one charge begins to last only a few tens of minutes of glow. And often during charging with the flashlight on, the LEDs burn out one after another. Of course, given the low price of the flashlight, you can buy a new one every time, but it is more advisable to once understand the causes of failures, eliminate them in the existing flashlight and forget about the problem for many years.

Let us consider in detail the one shown in Fig. 1 diagram of one of the failed lamps and determine its main shortcomings. To the left of the GB1 battery there is a unit responsible for charging it. The charging current is set by the capacitance of capacitor C1. Resistor R1, installed in parallel with the capacitor, discharges it after disconnecting the flashlight from the network. The red LED HL1 is connected through a limiting resistor R2 in parallel with the lower left diode of the rectifier bridge VD1-VD4 in reverse polarity. Current flows through the LED during those half-cycles of the mains voltage in which the upper left diode of the bridge is open. Thus, the glow of the HL1 LED only indicates that the flashlight is connected to the network, and not that charging is in progress. It will glow even if the battery is missing or faulty.

The current consumed by the flashlight from the mains is limited by the capacitance of capacitor C1 to approximately 60 mA. Since part of it is branched into the HL1 LED, the charging current for the GB1 batteries is about 50 mA. Sockets XS1 and XS2 are designed to measure battery voltage.

Resistor R3 limits the battery discharge current through the LEDs EL1-EL5 connected in parallel, but its resistance is too small, and a current exceeding the rated current flows through the LEDs. This increases the brightness slightly, but the rate of degradation of LED crystals increases noticeably.

Now about the reasons for LED burnout. As you know, when charging an old lead battery whose plates have been sulfated, an additional voltage drop occurs across its increased internal resistance. As a result, during charging, the voltage at the terminals of such a battery or their battery can be 1.5...2 times higher than the nominal one. If at this moment, without stopping charging, you close switch SA1 to check the brightness of the LEDs, then the increased voltage will be sufficient for the current flowing through them to significantly exceed the permissible value. The LEDs will fail one by one. As a result, burned-out LEDs are added to the battery, which is unsuitable for further use. It is impossible to repair such a flashlight - there are no spare batteries on sale.

The proposed scheme for finalizing the lantern, shown in Fig. 2 allows you to eliminate the described shortcomings and eliminate the possibility of failure of its elements due to any erroneous actions. It consists in changing the connection circuit of the LEDs to the battery so that its charging is interrupted automatically. This is achieved by replacing switch SA1 with a switch. The limiting resistor R5 is selected such that the total current through the LEDs EL1-EL5 at a battery voltage of GB1 of 4.2 V is 100 mA. Since switch SA1 is a three-position switch, it became possible to implement an economical mode of reduced brightness of the flashlight by adding resistor R4 to it.

The indicator on the HL1 LED has also been redesigned. Resistor R2 is connected in series with the battery. The voltage that drops across it when the charging current flows is applied to the LED HL1 and the limiting resistor R3. Now the charging current flowing through the GB1 battery is indicated, and not just the presence of mains voltage.

The unusable gel battery was replaced by a composite of three Ni-Cd batteries with a capacity of 600 mAh. The duration of its full charge is about 16 hours, and it is impossible to damage the battery without stopping charging on time, since the charging current does not exceed a safe value, numerically equal to 0.1 of the nominal capacity of the battery.

Instead of the burnt ones, HL-508h338WC LEDs with a diameter of 5 mm of white light with a nominal brightness of 8 cd at a current of 20 mA (maximum current - 100 mA) and an emission angle of 15° were installed. In Fig. Figure 3 shows the experimental dependence of the voltage drop across such an LED on the current flowing through it. Its value of 5 mA corresponds to an almost completely discharged battery GB1. Nevertheless, the brightness of the flashlight in this case remained sufficient.

The lantern, converted according to the scheme considered, has been successfully operating for several years. A noticeable decrease in the brightness of the glow occurs only when the battery is almost completely discharged. This is precisely the signal that it needs to be charged. As is known, completely discharging Ni-Cd batteries before charging increases their durability.

Among the disadvantages of the considered modification method, we can note the rather high cost of a battery of three Ni-Cd batteries and the difficulty of placing it in the flashlight body instead of the standard lead-acid one. The author had to cut the outer film shell of the new battery in order to more compactly place the batteries that form it.

Therefore, when finalizing another flashlight with four LEDs, it was decided to use only one Ni-Cd battery and LED driver on the ZXLD381 chip in the SOT23-3 package http://www.diodes.com/datasheets/ ZXLD381.pdf. With an input voltage of 0.9...2.2 V, it provides LEDs with a current of up to 70 mA.

In Fig. Figure 4 shows the power supply circuit for LEDs HL1-HL4 using this chip. A graph of the typical dependence of their total current on the inductance of inductor L1 is shown in Fig. 5. With its inductance of 2.2 μH (a DLJ4018-2.2 inductor is used), each of the four parallel-connected LEDs EL1-EL4 accounts for 69/4 = 17.25 mA current, which is quite enough for their bright glow.

Of the other add-on elements, only the Schottky diode VD1 and capacitor C1 are required to operate the microcircuit in the smoothed output current mode. It is interesting that on a typical diagram for using the ZXLD381 microcircuit, the capacity of this capacitor is indicated as 1 F. The battery charging unit G1 is the same as in Fig. 2. The limiting resistors R4 and R5, which are also there, are no longer needed, and switch SA1 only needs two positions.

Due to the small number of parts, the modification of the lantern was carried out by hanging installation. Battery G1 (Ni-Cd size AA with a capacity of 600 mAh) is installed in the appropriate holder. Compared to the lantern modified according to the scheme in Fig. 2, the brightness turned out to be subjectively somewhat lower, but quite sufficient.

Date of publication: 05/31/2013

Readers' opinions

No comments yet. Your comment will be the first.

You can leave your comment, opinion or question on the above material:

www.radioradar.net

The other day a neighbor came over and brought with her a cute portable flashlight.
The lantern worked for six months, lay idle for six months, now it is needed, but does not work. The lantern was used in the basement; the light bulb is only above the door, and it’s gloomy near the distant shelves with jam and pickles. The lantern lived in the basement, hanging on the doorframe under the switch and socket. The basement is dry, the husband wanted to make a carrier with a light bulb, but a lantern appeared - there was no need for it. While the women were gossiping among themselves, I busied myself with the lantern. The flashlight was made by the Chinese, there is a helium acid battery,
halogen incandescent lamp, charger for recharging the battery,
assembled according to a primitive scheme.

I took the necessary measurements of the battery with a multimeter:

Voltage and current are zero, resistance is infinity. There is no point in fiddling with such a battery, I had the opportunity to try to revive it, but if it died, it died. It was decided to make a simple flashlight with an LED, powered by 220 volts.
A neighbor brought a power cord about five meters with a plug at one end.
I found a 12 volt LED light bulb.
a working board from the required charger was also available,
I installed only a D815D zener diode instead of the indicator LED, Yes, I soldered the power cord to the board.
He stuck the plug into the network and the gentle light of the lantern illuminated the room.
The deal was only worth a ruble and a half, but I received a three-liter jar of assorted pickled vegetables as a present from a neighbor.

usamodelkina.ru

LED flashlight from 1.5 V and below

The blocking generator is a generator of short-term pulses repeated at fairly large intervals of time.

One of the advantages of blocking generators is their comparative simplicity, the ability to connect a load through a transformer, high efficiency, and connection of a sufficiently powerful load.

Blocking oscillators are very often used in amateur radio circuits. But we will run an LED from this generator.

Very often when hiking, fishing or hunting you need a flashlight. But you don’t always have a battery or 3V batteries at hand. This circuit can run the LED at full power from a nearly dead battery.

A little about the scheme. Details: any transistor (n-p-n or p-n-p) can be used in my KT315G circuit.

The resistor needs to be selected, but more on that later.

The ferrite ring is not very large.

And a high-frequency diode with a low voltage drop.

So, I was cleaning out a drawer in my desk and found an old flashlight with an incandescent bulb, burnt out, of course, and recently I saw a diagram of this generator.

And I decided to solder the circuit and put it in a flashlight.

Well, let's get started:

First, let's assemble according to this scheme.

We take a ferrite ring (I pulled it out from the ballast of a fluorescent lamp) and wind 10 turns of 0.5-0.3 mm wire (it could be thinner, but it won’t be convenient). We wound it, make a loop, or a branch, and wind it another 10 turns.

Now we take the KT315 transistor, an LED and our transformer. We assemble according to the diagram (see above). I also placed a capacitor in parallel with the diode, so it glowed brighter.

So they collected it. If the LED does not light, change the polarity of the battery. Still not lit, check that the LED and transistor are connected correctly. If everything is correct and still does not light up, then the transformer is not wound correctly. To be honest, my circuit didn’t work the first time either.

Now we complement the diagram with the remaining details.

By installing diode VD1 and capacitor C1, the LED will glow brighter.

The last stage is the selection of the resistor. Instead of a constant resistor, we put a 1.5 kOhm variable one. And we start spinning. You need to find the place where the LED shines brighter, and you need to find the place where if you increase the resistance even a little, the LED goes out. In my case it is 471 Ohm.

Okay, now closer to the point))

We disassemble the flashlight

We cut a circle from one-sided thin fiberglass to the size of the flashlight tube.

Now we go and look for parts of the required denominations of several millimeters in size. Transistor KT315

Now we mark the board and cut the foil with a stationery knife.

We tinker the board

We fix bugs, if any.

Now to solder the board we need a special tip, if not, it doesn’t matter. We take wire 1-1.5 mm thick. We clean it thoroughly.

Now we wind it on the existing soldering iron. The end of the wire can be sharpened and tinned.

Well, let's start soldering the parts.

You can use a magnifying glass.

Well, everything seems to be soldered, except for the capacitor, LED and transformer.

Now test run. We attach all these parts (without soldering) to the “snot”

Hooray!! Happened. Now you can solder all the parts normally without fear

I suddenly became interested in what the output voltage was, so I measured

3.7V is normal for a high power LED.

The most important thing is to solder the LED))

We insert it into our flashlight; when I inserted it, I unsoldered the LED - it was in the way.

And so, we inserted it and made sure that everything would fit freely. Now we take out the board and cover the edges with varnish. So that there is no short circuit, because the body of the flashlight is a minus.

Now we solder the LED back and check again.

Checked, everything works!!!

Now we carefully insert all this into the flashlight and turn it on.

Such a flashlight can be started even from a dead battery, or if there are no batteries at all (for example, in the forest while hunting). There are many different ways to get a small voltage (insert 2 wires of different metals into a potato) and start an LED.

Good luck!!!

sdelaysam-svoimirukami.ru

BATTERY LED

It was evening, there was nothing. And I started cleaning up my deposits of radio components and other electronic things that had accumulated around the table. Some will go to the barn, and some will go to the sofa. And in the process of putting things in order, I came across a simple burnt-out LED flashlight with a battery charged from a built-in transformerless rectifier.

Since the LEDs themselves turned out to be alive, and the case seemed fine, I decided to bring it to working condition. Of course, not according to the original Chinese scheme, but according to a more advanced one. As planned, the updated rechargeable LED flashlight will be charged from the mains and shine for up to 20 hours from lithium-ion (at a current of 50 mA).

Don’t be afraid - you don’t need to solder expensive parts :) For these purposes, a ready-made charger from any mobile phone (I lost it a month ago) and also any Mobile lithium-ion battery (they gave away a phone drowned in the sea for spare parts) are perfect.

What needs to be done? Just connect the charger to the battery, and in turn connect it to the LEDs.

Since the flashlight had a small square hole for an additional LED, I covered it with a piece of dark plexiglass, placing a red LED underneath it to indicate that it was plugged in for recharging. The LED is switched on parallel to the memory outputs.

The original plug of the flashlight was lost, so I had to make a new one, having first sawed it off from the above-mentioned charger from which the scarf was removed.

As you can see, there was quite enough space in the case for both the charger and other components of the LED flashlight.

When installing, keep in mind that if the battery is directly soldered to the charger, then when disconnected from the network there will be a small self-discharge of a few milliamps. The solution is simple - add a diode like IN4001 or similar for a current of more than 0.5A.

Now, when you turn on the flashlight with the toggle switch, the battery plus goes through a 20 Ohm resistor to the LEDs. And by pressing the toggle switch again and transferring the plus to the battery, we switch the flashlight to mains charging mode.

Despite the fact that the battery itself has a charge controller, I do not recommend leaving the flashlight plugged into an outlet for more than 5 hours. You never know...

The finished LED rechargeable flashlight turned out to be very nice and easy to use. It's bright enough for most purposes. Who needs extra power - look at powerful LEDs.

Here, using this simple design as an example, I showed the very principle of remaking lanterns using leftovers from non-working mobile phones, of which I am sure you have accumulated a considerable amount.

LED Flashlights Forum

Discuss the article BATTERY LED

radioskot.ru

We restore and bring to life a Chinese lantern. / Workshop / Not Lost

Many people have various Chinese lanterns that run on a single battery. Like this: Unfortunately, they are very short-lived. I will tell you further about how to bring a flashlight back to life and about some simple modifications that can improve such flashlights. The weakest point of such flashlights is the button. Its contacts oxidize, as a result of which the flashlight begins to shine dimly, and then may stop turning on altogether. The first sign is that a flashlight with a normal battery shines dimly, but if you click the button several times, the brightness increases. The easiest way to make such a lantern shine is to do the following: 1. Take a thin stranded wire and cut off one strand. 2. We wind the wires onto the spring. 3. We bend the wire so that the battery does not break it. The wire should protrude slightly above the screw part of the flashlight. 4. Twist tightly. We break off (tear off) the excess wire. As a result, the wire ensures good contact with the negative part of the battery and the flashlight will shine with the proper brightness. Of course, the button is not available for such repairs, so turning the flashlight on and off is done by turning the head part. My Chinese guy worked like this for a couple of months. If you need to change the battery, do not touch the back of the flashlight. We turn our heads away.

RESTORING THE OPERATION OF THE BUTTON.

Today I decided to bring the button back to life. The button is located in a plastic case, which is simply pressed into the back of the flashlight. In principle, it can be pushed back, but I did it a little differently: 1. Use a 2 mm drill to make a couple of holes to a depth of 2-3 mm.2. Now you can use tweezers to unscrew the housing with the button.3. Remove the button.4. The button is assembled without glue or latches, so it can be easily disassembled with a stationery knife. The photo shows that the moving contact has oxidized (a round thing in the center that looks like a button). It can be cleaned with an eraser or fine sandpaper and put the button back together, but I decided to tin it additionally both this part and the fixed contacts.1. Clean with fine sandpaper.2. Apply a thin layer to the areas marked in red. We wipe off the flux with alcohol and assemble the button.3. To increase reliability, I soldered a spring to the bottom contact of the button.4. We put everything back together. After the repair, the button works perfectly. Of course, tin also oxidizes, but since tin is a fairly soft metal, I hope that the oxide film will be easily destroyed when the button is used. It’s not for nothing that the central contact on light bulbs is made of tin.

IMPROVING FOCUS.

My Chinese guy had a very vague idea of ​​what a “hotspot” was, so I decided to enlighten him. Unscrew the head part.1. There is a small hole in the board (arrow). Using an awl, unscrew the filling while lightly pressing your finger on the outside of the glass. This makes it easier to unscrew.2. Remove the reflector.3. We take ordinary office paper, punch 6-8 holes with an office hole punch. The diameter of the hole punch holes perfectly matches the diameter of the LED. Cut out 6-8 paper washers.4. Place the washers on the LED and press them with the reflector. Here you will have to experiment with the number of washers. I improved the focusing of a couple of flashlights in this way; the number of washers was in the range of 4-6. The current patient required 6 of them. What happened in the end: On the left is our Chinese, on the right is Fenix ​​LD 10 (at minimum). The result is quite pleasant. The hotspot became pronounced and uniform.

INCREASE THE BRIGHTNESS (for those who know a little about electronics).

The Chinese save on everything. A couple of extra details will increase the cost, so they don’t install it. The main part of the diagram (marked in green) may be different. On one or two transistors or on a specialized microcircuit (I have a circuit of two parts: a choke and a microcircuit with 3 legs, similar to a transistor). But they save money on the part marked in red. I added a capacitor and a pair of 1n4148 diodes in parallel (I didn't have any shots). The brightness of the LED increased by 10-15 percent.

1. This is what the LED looks like in similar Chinese ones. From the side you can see that there are thick and thin legs inside. The thin leg is a plus. You need to be guided by this sign, because the colors of the wires can be completely unpredictable.2. This is what the board looks like with the LED soldered to it (on the back side). Green color indicates foil. The wires coming from the driver are soldered to the legs of the LED.3. Using a sharp knife or a triangular file, cut the foil on the positive side of the LED. Sand the entire board to remove the varnish.4. Solder the diodes and capacitor. I took the diodes from a broken computer power supply, and soldered the tantalum capacitor from some burnt-out hard drive. The positive wire now needs to be soldered to the pad with the diodes.

As a result, the flashlight produces (by eye) 10-12 lumens (see photo with hotspots), judging by the Phoenix, which produces 9 lumens in minimum mode.

And the last thing: the advantage of the Chinese over a branded flashlight (yes, don’t laugh) Branded flashlights are designed to use batteries, so with the battery discharged to 1 volt, my Fenix ​​LD 10 simply won’t turn on. Absolutely. I took a dead alkaline battery that had served its life in the computer mouse. The multimeter showed that it had dropped to 1.12v. The mouse no longer worked on it, Fenix, as I said, did not start. But the Chinese one works! On the left is the Chinese, on the right is the Fenix ​​LD 10 at minimum (9 lumens). Unfortunately, the white balance is off. The phoenix has a temperature of 4200K. The Chinese is blue, but not as bad as in the photo. Just for fun, I tried to finish off the battery. At this brightness level (5-6 lumens by eye), the flashlight worked for about 3 hours. The brightness is quite enough to illuminate your feet in a dark entrance/forest/basement. Then for another 2 hours the brightness decreased to the “firefly” level. Agree, 3-4 hours with acceptable light can solve a lot. For this, let me bow out. Stari4ok.

Hh004F connection diagram

Light sensor connection diagram for lighting

Currently, power outages have become very frequent, so in amateur radio literature a lot of attention is paid to local power sources. Not very energy-intensive, but very useful during emergency shutdowns, is a compact rechargeable flashlight (AKF), the battery of which uses three sealed nickel-cadmium disk batteries D 0.25. The failure of the ACF for one reason or another causes considerable disappointment. However, if you apply a little ingenuity, understand the design of the flashlight itself and know basic electrical engineering, then it can be repaired, and your little friend will serve you for a long time and reliably.

Circuit design. Design

Let's start, as expected, by studying the instruction manual 2.424.005 R3 Rechargeable flashlight "Electronics V6-05". Inconsistencies begin immediately after a careful comparison of the electrical circuit diagram (Fig. 1) and the design of the flashlight. In the circuit, the plus comes from the battery, and the minus is connected to the HL1 light bulb.

In reality, the coaxial terminal HL1 is permanently connected to the plus of the battery, and the minus is connected through S1 to the threaded socket. Having carefully examined the installation connections, we immediately notice that HL1 is not connected according to the diagram, capacitor C1 is not connected to VD1 and VD2, as shown in Fig. 1, but to the elastic contact of the structure, pressing the minus battery, which is structurally and technologically convenient, since C1, as the largest element, it is quite rigidly mounted with structural elements - one of the pins of the power plug, structurally combined with the ACF housing and the battery spring contact; resistor R2 is not connected in series with capacitor C1, but is soldered with one end to the second pin of the power plug, and the other to the holder. U1. This is also not taken into account in the ACF scheme in . The remaining connections correspond to the diagram shown in Fig. 2.

But if you do not take into account the design and technological advantages, which are quite obvious, then in principle it does not matter how C1 is connected, according to Fig. 1 or Fig. 2. By the way, with a good idea to refine the AKF charger circuit, it was not possible to avoid the use of “extra” elements.

The memory circuit, while maintaining the general algorithm, can be significantly simplified by assembling it according to Fig. 3.

The difference is that elements VD1 and VD2 in the diagram in Fig. 3 perform two functions, which made it possible to reduce the number of elements. Zener diode VD1 for the negative half-wave of the supply voltage on VD1, VD2 serves as a rectifier diode, it is also a source of positive reference voltage for the comparison circuit (CC), the (second) function of which is also performed by VD2. CC works as follows: when the EMF value at the cathode VD2 is less than the voltage at its anode, the normal process of charging the battery occurs. As the battery charges, the EMF value on the battery increases, and when it reaches the voltage at the anode, VD2 will close and the charge will stop. The value of the reference voltage VD1 (stabilization voltage) must be equal to the sum of the voltage drop in the forward direction across VD2 + voltage drop across R3VD3 + battery emf and is selected for a specific charge current and specific elements. The emf of a fully charged disk is 1.35 V.

With this charging scheme, the LED, as an indicator of the battery charge state, lights up brightly at the beginning of the process, as it charges, its brightness decreases, and when it reaches full charge, it goes out. If during operation it is noticed that the product of the charge current and the glow time of VD3 in hours is significantly less than the value of its theoretical capacity, then this does not indicate that the comparator on VD2 is not working correctly, but that one or more disks have insufficient capacity.

terms of Use

Now let's analyze the charge and discharge of the battery. According to specifications (12MO.081.045), the charging time for a completely discharged battery at a voltage of 220 V is 20 hours. The charging current at C1 = 0.5 μF, taking into account the spread in capacity and fluctuations in the supply voltage, is about 25-28 mA, which corresponds to the recommendations, and The recommended discharge current is twice the charging current, i.e. 50

mA. The number of complete charge-discharge cycles is 392. In a real ACF design, the discharge is carried out on a standard 3.5 V x 0.15 A light bulb (with three disks), although it gives an increase in brightness, but also due to an increase in current from the battery in excess of that recommended by the specifications , negatively affects the service life of the battery, so such a replacement is hardly advisable, since in some copies of the disks this can cause increased gas formation, which in turn will lead to an increase in pressure inside the housing and to a deterioration in the internal contact made by the disc spring between the tablet package active substance and the minus part of the body. This also leads to the release of electrolyte through the seal, causing corrosion and associated deterioration of contact both between the disks themselves and between the disks and the metal elements of the AKF structure.

In addition, due to leakage, water evaporates from the electrolyte, resulting in an increase in the internal resistance of the disk and the entire battery. With further operation of such a disk, it completely fails as a result of the conversion of the electrolyte partly into crystalline KOH, partly into potash K2CO3. It is for these reasons that special attention must be paid to charge-discharge issues.

Practical repair

So, one of the three batteries has gone bad. You can assess its condition with an Avometer. To do this (in the appropriate polarity), each disk is briefly short-circuited with the probes of an avometer set to measure direct current within 2-2.5 A.

For good, freshly charged disks, the short-circuit current should be within 2-3 A. When repairing an ACF, two logical options may arise: 1) there are no spare disks; 2) there are spare disks.

In the first case, this solution will be the simplest. Instead of the third, unusable disk, a washer is installed from the copper body of an unusable transistor of the KT802 type, which, moreover, fits well in size into most AKF designs. To make a washer, remove the terminals of the transistor electrodes and clean both ends with a fine file from the coating until copper appears, then they are ground on fine-grained sanding paper laid on a flat plane, after which they are polished to a shine on a piece of felt with an applied layer of GOI paste. All these operations are necessary to reduce the influence of contact resistance on the combustion time. The same applies to the contact ends of the disks, the darkened surfaces of which during operation are desirable to be sanded for the same reasons.

Since removing one disk will lead to a decrease in the brightness of the HL1 glow, a 2.5 V light bulb at 0.15 A is installed in the AKF or, even better, a 2.5 V light bulb at 0.068 A, which, although it has less power, reduces the current discharge makes it possible to bring it closer to that recommended by the specifications, which will have a beneficial effect on the life of the battery disks. Practical disassembly and analysis of correctable causes of disk failure showed that quite often the cause of failure is the destruction of the disc spring. Therefore, do not rush to throw away an unusable disk and, if you are lucky, you can make it work some more. This operation will require sufficient accuracy and certain plumbing skills.

To carry it out, you will need a small bench vice, a ball from a ball bearing with a diameter of about 10 mm and a smooth steel plate 3-4 mm thick. The plate is placed through a 1mm thick electrical cardboard gasket between the jaws and the positive part of the body, and the ball is placed between the second jaw and the negative part of the body, orienting the ball approximately at its center. The electrical cardboard gasket is designed to eliminate short circuits of the disk, and the plate is designed to uniformly distribute the force and prevent deformation of the positive part of the battery case from notching on the jaws of the vice. Their size is obvious. Gradually tighten the vice. Having pressed the ball 1-2 mm, remove the disk from the device and control the short-circuit current. Usually, after one or two clamps, more than half of the charged disks begin to show an increase in short-circuit current up to 2-2.5 A. After a certain stroke, the clamping force increases sharply, which means that the deformable part of the housing rests on the tablet. Further pressing is impractical, since it leads to destruction of the battery. If after the stop the short-circuit current does not increase, then the disk is completely unusable.

In the second case, simply replacing the disk with another one may also not bring the desired result, since fully functional disks have so-called “capacitive” memory.

Due to the fact that when operating in a battery, there is always at least one disk that has less than the capacity value, which is why when it is discharged, the internal resistance sharply increases, which limits the possibility of complete discharge of the remaining disks. It is not advisable to subject such a battery to some recharging to eliminate this phenomenon, since this will not lead to an increase in capacity, but only to failure of the best drives. Therefore, when replacing at least one disk in a battery, it is advisable to subject them all to forced training (give one full charge-discharge cycle) to eliminate the above phenomena. The charge of each disk is carried out in the same ACF, using washers made of transistors instead of two disks.

The discharge is carried out on a resistor with a resistance of 50 Ohms, providing a discharge current of 25 mA (which corresponds to the specifications), until the voltage across it reaches 1 V. After this, the disks are combined into a battery and charged together. Having charged the entire battery, discharge it to the standard HL until the battery reaches 3 V. Under a load of the same HL, check the short-circuit current of each disk discharged to 1 V again.

For disks suitable for operation as part of a battery, the short-circuit current of each disk should be approximately the same. The battery capacity can be considered sufficient for practical use if the discharge time to 3 V is 30-40 minutes.

Details

Fuse.U1. Having observed the evolution of ACF circuitry during repairs for about two decades, it was noticed that in the mid-80s, some enterprises began to produce batteries without fuses with a current-limiting resistor of 0.5 W and a resistance of 150-180 Ohms, which is quite justified, since in the event of a breakdown The C1 role. U1 was played by R2 (Fig. 1) or R2 (Fig. 2 and 3), the conductive layer of which evaporated much earlier (than U1 burned at 0.15 A), interrupting the circuit, which is what is required from the fuse. Practice confirms that if a current-limiting resistor with a power of 0.5 W in a real ACF circuit heats up noticeably, then this clearly indicates a significant leakage C1 (which is difficult to determine with an avometer, and also due to changes in its value over time), and it must be replaced .

Capacitor C1 type MBM 0.5 μF at 250 V is the most unreliable element. It is designed for use in DC circuits with the appropriate voltage, and the use of such capacitors in AC networks, when the voltage amplitude in the network can reach 350 V, and taking into account the presence in the network of numerous peaks from inductive loads, as well as the charging time of a completely discharged ACF according to the specifications (about 20 hours), then its reliability as a radio element becomes very low. The most reliable capacitor, which has optimal dimensions that allow it to fit into ACFs of various design sizes, is the capacitor K42U-2 0.22 μF Ch ​​630 V or even K42U 0.1 μF Ch ​​630 V. Reducing the charging current to approximately 15-18 mA, at 0.22 μF and up to 8-10 mA at 0.1 μF, practically only causes an increase in its charging time, which is not significant.

LED indicator of charging current VD3. In ACFs that do not have an LED indicator of the charge current, it can be installed by connecting it to the open circuit at point A (Fig. 2).

The LED is connected in parallel with the measuring resistor R3 (Fig. 4), which must be selected when making a new one or reducing C1. With capacitance C1 equal to 0.22 μF instead of 0.5 μF, the brightness of VD3 will decrease, and at 0.1 μF VD3 may not light up at all. Therefore, taking into account the above charge currents, in the first case, resistor R3 must be increased in proportion to the decrease in current, and in the second case, it must be removed completely. In practice, taking into account the fact that working with 220 V is very unsafe, it is better to select the resistance R3 by connecting an adjustable direct current source (RIPS) through a milliammeter to point B (Fig. 3), and controlling the charge current. Instead of R3, a potentiometer with a resistance of 1 kOhm is temporarily connected, turned on by a rheostat to the minimum resistance. By increasing the RIPT voltage, the battery charging current is set to 25 mA.

Without changing the set voltage of the RIPT, connect the milliammeter to the open circuit VD3 at point C and, gradually increasing the resistance of the potentiometer, achieve a current through it of 10 mA, i.e. half of the maximum for AL307. This point is especially important for circuits without a zener diode, in which, at the first moment after switching on when charging C1, the current through VD3 can become large, despite the presence of a current-limiting resistor R1, and can lead to VD3 failure. In steady state, R1 has virtually no effect on the charge current due to its low resistance compared to the reactive (about 9 kOhm) resistance C1. When modifying, VD3 is installed in a hole with a diameter of 5 mm, drilled symmetrically to the parting line in the housing between the supports of the spring contact connected to the coaxial terminal HL1 and the battery positive. The measuring resistor is placed there.

Rectifier diodes

Considering the presence of a current surge during the initial charge of C1, to increase reliability in the AKF rectifier, it is advisable to use any silicon pulse diodes with a reverse voltage of 30 V or more.

Non-standard use of ACF

By making an adapter from the base of an unusable light bulb and the power connector of a radio receiver, the AKF can be used not only as a light source, but also as a source of secondary power supply with a voltage of 3.75 V. At an average volume level (consumption current 20-25 mA), its capacity is quite sufficient for listening to VEF for several hours.

In some cases, in the absence of electricity, the ACF can be recharged from a radio broadcast line. Owners of AKF with an LED indicator can observe the process of dynamic blinking of the LED. VD3 burns especially smoothly from “heavy” rock, so if you don’t like listening, charge the ACF, use the energy for peaceful purposes. The physical meaning of this phenomenon is that reactance decreases with increasing frequency, therefore, at a significantly lower voltage (15-30 V), the pulsed value of the charge current through the indicator is sufficient for it to glow and, naturally, recharge.

Literature:

1. Vuzetsky V.N. Charger for a rechargeable flashlight // Radioamator. - 1997. - No. 10. - P. 24.
2. Tereshchuk R.M. and others. Semiconductor receiving and amplifying devices: Reference. radio amateur. - Kyiv: Nauk. Dumka, 1988

Such an abundance of shapes, sizes, and colors is perhaps not found in any other group of products. There are already at least five of them at home, but I bought one more. And not at all out of curiosity, I looked at it and my imagination drew a picture of how in the dark I turn on the side panel, attach the end part with a magnet to a metal garage door, and in the light, with my hands free, I open the locks. Service - “five stars”! But it was offered to buy the lantern in non-working condition.

Characteristics of the flashlight STE-15628-6LED

• 6 LEDs (3 in reflector + 3 in side panel)
• 2 operating modes
• built-in memory
• magnet for fastening
• dimensions: 11x5x5 cm

Externally, an absolutely serviceable and attractive product did not create a luminous flux. Well, is it really possible that such a wonderful thing could be completely useless? This model was in a single copy, but the electronics lover in me “broadcast” that everything was surmountable.

The wire came off when the case was opened, but the plastic was already scorched and suggested that the electronic components of the charger circuit were burnt, and the battery may be quite good.

I started checking with him. The voltmeter showed the voltage at the terminals to be one volt. Having already had some experience with such batteries, I began by opening the top safety strip on it, removing the rubber caps, adding one cube of distilled water to each “jar” and putting it on charge. Charging voltage 12 V, current 50 mA.

Charging in high voltage mode (instead of the standard 4.7 V) lasted two hours, more than 4 volts available.

If the battery is serviceable, then it needs a charger assembled according to a more decent circuit and on more reliable electronic components than from the Chinese manufacturer, in which the input resistor “burnt out”, one of the two 1N4007 rectifier diodes was broken and smoked when turned on LED memory resistor. First of all, you need a reliable capacitor of at least 400 volts, a diode bridge and a suitable zener diode at the output.

Flashlight memory circuit

The compiled circuit showed its performance, a capacitor with a capacity of 1 μF and 400 V was found by MBGO (much more reliable and fits well into the intended case), the diode bridge was assembled from 4 pieces of 1N4007 diodes, the zener diode was tested by the first imported one that came across (the stabilization voltage was determined by the attachment to multimeter, but it was not possible to read its name).

Next, the circuit was assembled by soldering and used to produce a normal charge cycle for a previously discharged battery (a milliammeter with a shunt, so in reality the full deflection of the needle occurs at a current of 50 mA). The zener diode is already used with a stabilization voltage of 5 V.

Printed circuit board for final assembly of the charger with dimensions for a cell phone charging case. I can't think of a better case option here.

Looks like a really assembled, functional board. The capacitor body is glued to the board with master glue. But I was too lazy to pick out the scarf, I’m sorry, I accidentally happened to have a used one of almost the right size on hand and this circumstance decided everything.

But I was not too lazy to replace the information sticker on the charging case. With a fully charged battery, in the dark, the side panel quite well illuminates a room measuring 10 square meters. meters, and the light from the headlight reflector makes objects clearly visible at a distance of up to 10 meters.

In the future I plan to choose a more reliable one for the flashlight. Author - Babay from Barnaula.

Flashlight circuit with battery

As a radio mechanic, I am interested in the simplest electronic devices. This time we will talk about a flashlight with a battery.

Here is a diagram of a flashlight with a battery.

The flashlight consists of two parts. In one part there is a battery and a mains charger, and in the other there is a switch and an incandescent lamp. To charge the battery, one part of the flashlight is disconnected from the head (where the lamp and switch are) and connected to a 220V network.

The photo shows an adapter connector that connects the battery and the switch to the incandescent lamp.

The design of such a flashlight is extremely simple. To charge a lead-acid battery G1 with a capacity of 1 A/h (1 ampere-hour) and a voltage of 4V, a circuit with a quenching capacitor C1 is used. Most of the 220V network voltage drops on it. Then the alternating voltage after the quenching capacitor is rectified by a diode bridge using diodes VD1 - VD4 (1N4001).

To smooth out ripples, an electrolytic capacitor C2 is installed after the diode bridge. The load for this entire rectifier is battery G1. If you turn it off, the rectifier output will have a voltage of about 300 volts, although when the battery is connected, the voltage at its output is 4 - 4.5 volts.

It is worth noting that the circuit with a damping (ballast) capacitor is simple, but quite dangerous. The fact is that such a circuit is not galvanically isolated from the 220 volt network. When using a transformer, the circuit becomes more electrically safe, but due to the high cost of this part, a circuit with a quenching capacitor is used.

The VD5 diode is necessary so that when the circuit is disconnected from the network, the battery does not discharge through the rectifier circuit and indication on the red LED HL1 and resistor R2. But the EL1 incandescent lamp (or a circuit of LEDs) is connected to the battery only through switch SA1. It turns out that the VD5 diode serves as a kind of barrier that passes current to the battery from the mains rectifier, but not back. This is such a simple defense. It is also worth saying that a small part of the rectified voltage is lost on the VD5 diode - due to the voltage drop across the diode when connected directly ( V F). It is somewhere between 0.5 - 0.7 volts.

I would also like to say something about the battery. As stated, it is sealed lead acid (Pb). Consists of two 2 volt cells connected in series. That is, the battery, as they say, consists of 2 cans.

The battery indicates that the maximum charge current is 0.5 amperes. Although for lead Pb batteries it is recommended to limit the charge current to 0.1 of its capacity. Those. for this battery, the best charging current will be 100mA (0.1A).

Typical problems with battery-powered flashlights are:

Failure of mains rectifier elements (diodes, electrolytic capacitor, resistor in the indication circuit);

Malfunction of the switch button (easily repaired by any suitable latching button or rocker switch);

Battery degradation (aging);

Worn contact connectors.

Click Class

Tell VK

An electric flashlight refers to an additional auxiliary tool for carrying out any work in the presence of poor lighting or no lighting at all. Each of us chooses the type of flashlight at our own discretion:

• Head Torch;
• pocket flashlight;
• hand generator flashlight

Diagram of a simple flashlight

The electrical circuit of a simple flashlight \Fig. 1\ consists of:

• battery cells;
• light bulbs;
• key\switch\.

The scheme is simple in its implementation and does not require any explanation. The reasons for a flashlight malfunction with this scheme may be:

• oxidation of contact connections with batteries;
• oxidation of light bulb socket contacts;
• oxidation of the contacts of the light bulb itself;
• malfunction of the key\light switch\;
• malfunction of the light bulb itself \bulb burnt out\;
• lack of contact connection with the wire;
• lack of battery power.

Other causes of malfunction may be any mechanical damage to the flashlight body.

LED rechargeable flashlight circuit

headlamp with LEDs BL - 050 - 7C

The BL - 050 - 7C flashlight goes on sale with a built-in charger; when such a flashlight is connected to an external AC voltage source, the battery is recharged.

Rechargeable batteries, or rather electrochemical batteries, - the principle of charging such elements is based on the use of reversible electrochemical systems. Substances formed during battery discharge under the influence of electric current are capable of restoring their original state. That is, we recharged the flashlight and we can continue to use it. Such electrochemical batteries or individual elements may consist of a certain amount, depending on the voltage consumed:

• number of light bulbs;
• type of light bulbs.

A quantity, a set of such individual elements of a flashlight, constitutes a battery.

The electrical circuit of a flashlight \Fig. 2\ can be considered as consisting of a simple incandescent light bulb or a certain number of LED light bulbs. For any flashlight circuit, what exactly is important? — It is important that the energy consumed by the light bulbs in the electrical circuit corresponds to the output voltage of the power source \battery, consisting of individual elements\.

Reading the connection diagram:

Resistor R1 with a resistance of 510 kOhm and a nominal power value of 0.25 W in the electrical circuit is connected in parallel, due to this high resistance, the voltage in the further section of the electrical circuit is significantly lost, or rather, part of the electrical energy is converted into thermal energy.

From resistor R2 with a resistance of 300 Ohms and a rated power value of 1 W, current is supplied to the LED VD2. This LED serves as an indicator light indicating the connection of the flashlight charger to an external AC voltage source.

Current flows to the anode of diode VD1 from capacitor C1. A capacitor in an electrical circuit is a smoothing filter; part of the electrical energy is lost during the positive half-cycle of the sinusoidal voltage, since during this half-cycle the capacitor is charged.

With a negative half-cycle, the capacitor is discharged and current flows to the anode of the cathode VD1. An external voltage drop for a given electrical circuit occurs when there are two resistors and a light bulb in the electrical circuit. You can also take into account that when the current passes from the anode to the cathode - in diode VD1 - there is also its own potential barrier. That is, the diode also tends to be subjected to some degree of heating, which causes an external voltage drop.

The GB1 battery, consisting of three elements, receives a current of two potentials \+ -\ from the charger \when the flashlight is connected to an external alternating voltage source\. In the battery, the electrochemical composition of the battery is restored to its original state.

The following circuit \Fig. 3\, which is found in LED flashlights, consists of the following electronic elements:

• two resistors \R1; R2\;
• diode bridge consisting of four diodes;
• capacitor;
• diode;
• LED;
• key;
• batteries;
• light bulbs.

For a given circuit, the external voltage drop occurs due to all the electronic elements connected in this circuit. One diagonal of the diode bridge of the bridge circuit is connected to an external AC voltage source, the other diagonal of the diode bridge is connected to a load - consisting of a certain number of light-emitting diodes.

All detailed descriptions of replacing electronic elements when repairing a flashlight, as well as diagnosing these elements, can be found on this site, which contains similar topics that cover the repair of household appliances.

How to repair an LED flashlight

In my work I sometimes have to use a headlamp. About six months after purchase, the flashlight's battery stopped charging after turning it on for recharging via the power cord.

When determining the cause of the headlamp failure, the repair was accompanied by photographs to present this topic in a clear example.

The cause of the malfunction was not clear at first, since when the flashlight was turned on to recharge, the signal light would light up and the flashlight itself would emit a weak light when the switch button was pressed. So what could be the reason for such a malfunction? Battery failure or some other reason?

It was necessary to open the flashlight housing to inspect it. In the photographs \photo No. 1\ the tip of a screwdriver indicates the places of fastening \connection\ of the body.

If the flashlight body cannot be opened, you need to carefully inspect to see if all the screws have been removed.

Photo #2 shows a step-down converter in both voltage and current.

You should not look for the cause of the malfunction in the circuit, since when connected to an external source, the signal light lights up \photo No. 2 red LED light\. Let's check the connections further.

In front of us in the photograph \photo No. 3\ there is a light switch for an LED flashlight. The contacts of the push-button switch post are a double light switch device, where for this example the following lights up:

• six LED lamps,
• twelve LED lamps

flashlight. As we can see, the two contacts of the switch are short-circuited and a common wire is soldered to these contacts. Two wires are soldered to the following two contacts of the switch - separately, from which current is supplied to the lighting:

• six lamps;
• twelve lamps.

It is enough to check the light switch contacts \when switching\ with a probe as shown in photograph No. 4. We touch the common contact \two short-circuited contacts\ with a finger and alternately touch the other two contacts with a probe.

If the switch is working properly, the LED light of the probe lights up \photo No. 4\. The light switch is working properly, we carry out further diagnostics.

The power cord can also be checked here with a probe \photo No. 5\. To do this, you need to short-circuit the pins of the plug with your finger and connect the probe alternately to the first and second contacts of the cable connector. If the probe light comes on, it will indicate that there is no break in the power cord wire.

The power cord for recharging the battery is working properly, we carry out further diagnostics. You should also check the flashlight battery.

The enlarged image of the battery \photo No. 6\ shows that a constant voltage of 4 Volts is supplied to recharge it. The current strength of this voltage is 0.9 ampere/hour. Checking the battery.

The multimeter device in this example is set to the DC voltage measurement range from 2 to 20 Volts so that the measured voltage corresponds to the set range.

As we can see, the device display shows a constant battery voltage of 4.3 Volts. In fact, this indicator should take a higher value - that is, there is insufficient voltage to power the LED lamps. LED lamps take into account potential barrier for each such lamp, as we know from electrical engineering. Consequently, the battery does not receive the required voltage when recharging.

And here is the whole reason for the malfunction \photo No. 8\. This cause of the malfunction was not immediately established - a break in the contact connection of the wire with the battery.

What can be noted here:

The wires in this circuit are unreliable for soldering, since the thin cross-section of the wire does not allow it to be securely attached at the soldering point.

But even this cause of failure can be eliminated, the wiring was replaced with a more reliable section and the LED flashlight is currently operational and works flawlessly.

I consider the topic presented to be unfinished; examples will be given for you - repairs of other types of flashlights.

That's all for now.

Tweet

Tell VK

Click Class

I would call it “Notes of a Shitty Electrician”! The author simply does not understand how the circuit works, its elements, and confuses concepts. Using the example of the circuit in Fig. 2: R1 serves to discharge capacitor C1 after disconnecting the flashlight from the network for safety reasons. There is no “loss” of voltage “in the further section”; let the Author connect a voltmeter and look at it to make sure of this. Resistor R2 serves as a current limiter. The VD2 LED not only serves as an indicator, but also supplies positive potential to the + battery.
Capacitor C1 in this circuit is a damping filter (and not a smoothing filter), and it is on it that the excess alternating voltage is extinguished.
He also said a lot about the potential barrier - it’s funny to read. And the current is “current of two potentials”?! According to classical physics, current flows from positive to negative potential, and electrons move in the opposite direction.
Did the author go to school?
And he has this everywhere. Sad. But someone takes his “revelations” at face value.

Hello, povaga! My “Oblik 2077” flashlight with one LED stopped charging. I can’t find the diagram, but it’s something like in Figure 3. Difference: there is no capacitor C2, no diode VD5, two resistors and a board with three contacts are soldered to the switch SA1. I measured the voltage after the bridge - 2 volts, the battery is 4 volts, how can it be charged? Please help me with the operating diagram and electrical diagram. Thank you in advance, best regards, Doldin.