DIY flashlight charge indicator. Several simple LED power circuits
As a sample, let's take a rechargeable flashlight from the company "DiK", "Lux" or "Cosmos" (see photo). This pocket flashlight is small-sized, comfortable in the hand and has a fairly large reflector - 55.8 mm in diameter, the LED matrix of which has 5 white LEDs, which provides a good and large illumination spot.
In addition, the shape of the flashlight is familiar to everyone, and many from childhood, in a word - a brand. The charger is located inside the flashlight itself; you just need to remove the back cover and plug it into a power outlet. But nothing stands still and this flashlight design has also undergone changes, especially its internal filling. The latest model at the moment is DIK AN 0-005 (or DiK-5 EURO).
Earlier versions are DIK AN 0-002 and DIK AN 0-003, differing in that they contained disk batteries (3 pcs), Ni-Cd series D-025 and D-026, with a capacity of 250 mA/h, or model AN 0-003 - assembly of newer D-026D batteries with a higher capacity, 320 mAh and incandescent light bulbs of 3.5 or 2.5 V, with a current consumption of 150 and 260 mA, respectively. An LED, for comparison, consumes about 10 mA and even a matrix of 5 pieces is 50 mA.
Of course, with such characteristics, the flashlight could not shine for a long time; it lasted for a maximum of 1 hour, especially the first models.
What is it about the latest flashlight model DIK AN 0-005?
Well, firstly, there is an LED matrix of 5 LEDs, as opposed to 3 or an incandescent light bulb, which gives significantly more light with lower current consumption, and secondly, the flashlight costs only 1 1.2-inch modern Ni-MH battery -1.5 V and capacity from 1000 to 2700 mAh.
Some will ask, how can a 1.2 V AA battery “light up” the LEDs, because for them to shine brightly you need about 3.5 V? For this reason, in earlier models they placed 3 batteries in series and received 3.6 V.
But I don’t know who first came up with the idea, the Chinese or someone else, to make a voltage converter (multiplier) from 1.2 V to 3.5 V. The circuit is simple, in Chinese flashlights there are only 2 parts - a resistor and a similar radio component to a transistor marked - 8122 or 8116, or SS510, or SK5B. SS510 is a Schottky diode.
Such a flashlight shines well, brightly, and what is not unimportant - for a long time, and the charge-discharge cycles are not 150, as in previous models, but much more, which increases the service life several times. But!! In order for an LED flashlight to serve for a long time, you need to insert it into a 220 V outlet when it is turned off! If this rule is not followed, then when charging you can easily burn out the Schottky diode (SS510), and often the LEDs at the same time.
I once had to repair a DIK AN 0-005 flashlight. I don’t know exactly what caused it to fail, but I assume that they plugged it into an outlet and forgot it for several days, although according to the passport it should be charged for no more than 20 hours. In short, the battery failed, leaked, and 3 out of 5 LEDs burned out, plus the converter (diode) also stopped working.
I had a 2700 mAh AA battery, left over from an old camera, as well as LEDs, but finding the part - SS510 (Schottky diode) - turned out to be problematic. This LED flashlight is most likely of Chinese origin and such a part can probably only be bought there. And then I decided to make a voltage converter from the parts that I had, i.e. from domestic ones: transistor KT315 or KT815, high-voltage transformer and others (see diagram).
The circuit is not new, it has existed for a long time, I just used it in this flashlight. True, instead of 2 radio components, like the Chinese, I got 3, but they were free.
The electrical circuit, as you can see, is elementary; the most difficult thing is to wind the RF transformer on a ferrite ring. The ring can be used from an old switching power supply, from a computer, or from an energy-saving non-working light bulb (see photo).
The outer diameter of the ferrite ring is 10-15 mm, thickness is approximately 3-4 mm. It is necessary to wind 2 windings of 30 turns each with a wire of 0.2-0.3 mm, i.e. we first wind 30 turns, then make a tap from the middle and another 30. If you take a ferrite ring from the board of a fluorescent light bulb, it is better to use 2 pieces, folded them together. The circuit will also work on one ring, but the glow will be weaker.
I compared 2 flashlights for glow, the original (Chinese) and the one converted according to the above scheme - I saw almost no difference in brightness. By the way, the converter can be inserted not only into a rechargeable flashlight, but also into a regular one that runs on batteries, then it will be possible to power it with just 1 1.5 V battery.
The flashlight charger circuit has undergone almost no changes, with the exception of the ratings of some parts. Charging current is approximately 25 mA. When charging, the flashlight must be turned off! And do not press the switch while charging, since the charging voltage is more than 2 times higher than the battery voltage, and if it goes to the converter and is amplified, the LEDs will have to be partially or completely changed...
In principle, according to the above diagram, you can easily make an LED flashlight with your own hands, by mounting it, for example, in the body of some old, even the most ancient flashlight, or you can make the body yourself.
And in order not to change the structure of the switch of the old flashlight, which used a small 2.5-3.5 V incandescent light bulb, you need to break the already burnt out light bulb and solder 3-4 white LEDs to the base, instead of the glass bulb.
And also, for charging, install a connector under the power cord from an old printer or receiver. But, I want to draw your attention, if the flashlight body is metal, do not mount the charger there, but make it remote, i.e. separately. It is not at all difficult to remove the AA battery from the flashlight and insert it into the charger. And don’t forget to insulate everything well! Especially in places where there is a voltage of 220 V.
I think that after the conversion, the old flashlight will serve you for many more years...
Dedicated to all those who have similar LED lights.
A typical problem with the latter is a 4-volt lead-acid (AGM) battery that “suddenly” stops working.
Recently there was a review with a solution to a similar problem. .
I took a slightly different path, it will become clear why later.
First, a little about the lanterns:
Budget flashlights with decent sizes and mediocre characteristics. But they continue to be bought and used. The flashlight contains many super-bright 3-5mm LEDs. 
LEDs are usually connected in parallel, through current-limiting resistors. 
The heart of the flashlight is a lead-acid battery (AGM) with a capacity of up to 4.5Ah. 
The unpretentiousness of the battery can be considered a positive point. Possibility of recharging at any time and operation at subzero temperatures. The last point is not taken into account in my modification, since the operation of the flashlight at significant negative temperatures is not planned.
Looking ahead, I’ll say that it took about 2 hours to remake the lantern.
Open the flashlight and remove the dead battery:
To begin with, I measured the current consumption at a battery voltage of 3.84 V:
Resistors are installed in series with the LEDs to limit the current. Due to the changed voltage of the flashlight, it would be possible to lower the resistance of the resistors, but I did not do this. The brightness has dropped slightly, you can live with this, and it’s time-consuming.
At a voltage of 4.2V, the current exceeded 1 A. This became the starting point in solving the problem. There is no need to use a cheap power bank kit due to the latter’s inability to produce the required current.
The solution was on the surface:
Two board options, one with overdischarge protection, the other without protection: 
A little about the boards. The controller is one of the most common TP4056. I used a similar board. Controller documentation. The controller provides a charging current of up to 1 Ampere, so you can roughly calculate the battery charging time.
Which board to use in your flashlight depends on the type of 18650 elements used. If there is overdischarge protection, then the one on the right. Otherwise, you can assign the battery protection function to the board, which it does an excellent job of. The boards differ from each other by the presence of additional parts, such as a DW01 discharge controller and an 8205 power switch (dual field-effect transistor) to disconnect the battery from the load at the right time or protect it from overcharging.
There is a lot of space inside, you can install at least a dozen batteries, but for testing I made do with one. 
The latter was removed from an old laptop battery and tested on an IMAX B6 charger: 
With a discharge current of 1 Ampere, the residual capacity is 1400 mAh. This is enough for about an hour and a half of continuous operation of the flashlight.
Let's try to connect the battery to the board:
The wires to the battery must be soldered carefully, without overheating the battery. If you are not sure, you can use a battery holder. 
It is also advisable to observe the color differentiation of the pants and use wires of different colors to connect the power.
We connect the board via a micro USB cable to the power supply:
The red LED lights up and the charge has started.
Now you need to install the charge controller board in the flashlight. There are no special fastenings, so we make a collective farm using everyone’s favorite superglue. 
Gluing your fingers at least once is the sacred duty of everyone who has used it.
We make a bracket from a suitable metal plate (an element from a children's metal construction set will do). 
In order to avoid short circuits, we use insulating material. I used a piece of heat shrink tubing.
I secured the board by first connecting the wires that previously went to the lead battery:
From the outside it looks like this:
Small defects are visible on the sides of the connector. They are corrected as follows: the hole or crack is filled with baking soda and then 1-2 drops of superglue. The glue sets instantly. After 30 seconds, you can use a file to process the surface.
We secure the battery inside using any available method. I used sealant; some people prefer a glue gun.
The charging connector hole will be covered later with a rubber cap.
We assemble and enable:
Works.
Upd: If you plan to connect several batteries in parallel, then before connecting, in order to avoid damage to the latter, it is necessary to bring all batteries to a single EMF (simple voltage).
Conclusions: Costs in money are approximately 100 rubles and 2 hours of time. I don’t take the battery into account; I used a half-dead one with high internal resistance. I get a working flashlight. The procedures I describe are not a panacea; there are other options for modifying flashlights. I did not display an indication of the charging process/readiness on the case. The blue/red LED glow is visible through the housing.
By the way, the board can have any mini or micro USB connector you like. It all depends on the availability of the necessary cables. Among other things, we still have a power supply on hand for charging a lead-acid battery - it will be useful to attach it somewhere.
Pros:
Working light, lighter weight (although this is an insignificant fact). You can charge in any accessible place if you have a USB charger or a computer.
Minuses:
The battery is afraid of frost, the brightness is lower (by about 10-15%) compared to the factory version. At the end of the discharge, the brightness drops, noticeably to the eye. To solve this problem, you can install a more capacious (or several) battery.
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 way to treat it is to tighten all the threads tightly.
If the flashlight doesn't 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 lights 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 often occurs due to oxidation of the aluminum surface of the ring or 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 this 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 negative goes through the body and is closed with 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 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) the 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 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 twisting part of the flashlight.
4. Twist tightly. We break off (tear off) the excess wire.
As a result, the wire provides good contact with the negative part of the battery and the flashlight
will shine with proper brightness. Of course, the button is no longer available for such repairs, so
Turning on and off the flashlight 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, the back of the flashlight
should not be touched. 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
It's just pressed into the back of the light. 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).
You can clean it with an eraser or fine sandpaper and put the button back together, but I decided to additionally tin 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,
assembling the button.
3. To increase reliability, I soldered a spring to the bottom contact of the button.
4. Putting everything back together.
After 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
easy to break down. It’s not for nothing that the central contact on light bulbs is made of tin.
IMPROVING FOCUS.
My Chinese friend 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). Use an awl to twist out the filling.
At the same time, lightly press your finger on the glass from the outside. This makes it easier to unscrew.
2. Remove the reflector.
3. Take ordinary office paper and punch 6-8 holes with an office hole punch.
The diameter of the holes in the hole punch matches perfectly with the diameter of the LED.
Cut out 6-8 paper washers.
4. Place the washers on the LED and press it 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.
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:
inductor and a 3-leg IC similar to a transistor). But they save 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.
We 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.
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-508H238WC 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.
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:
- Vuzetsky V.N. Charger for a rechargeable flashlight // Radioamator. - 1997. - No. 10. - P. 24.
- Tereshchuk R.M. and others. Semiconductor receiving and amplifying devices: Reference. radio amateur. - Kyiv: Nauk. Dumka, 1988
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