Surely every car enthusiast has had to assemble a car charger with his own hands. There are a lot of different approaches, ranging from simple transformer circuits to pulse circuits with automatic adjustment. The charger from the computer power supply just occupies the golden mean. It comes at a cheap price, and its parameters do an excellent job of charging car batteries. Today we will tell you how you can assemble a charger from an ATX computer power supply in half an hour. Go!

First you need a working power supply. You can take a very old one with 200 - 250 W, this power will be enough with a reserve. Considering that charging should occur at a voltage of 13.9 - 14.4 V, the most important modification in the unit will be raising the voltage on the 12 V line to 14.4 V. A similar method was used in the article: Charger from a power supply for LED strips.

Attention! In a working power supply, the elements are under dangerous voltage. Don't grab everything with your hands.

First of all, we unsolder all the wires that came out of the power supply. We leave only the green wire; it must be soldered to the negative contacts. (The areas from which the black wires came out are a minus.) This is done to automatically start the unit when connected to the network. I also immediately recommend soldering the wires with terminals to the negative and + 12 V bus (former yellow wires), for convenience and further setup of the charger.

The following manipulations will be performed with the PWM operating mode - for us it is a TL494 microcircuit (there are also a bunch of power supplies with its absolute analogues). We are looking for the first leg of the microcircuit (the lowest left leg), then we look at the track on the back of the board.

Three resistors are connected to the first pin of the microcircuit; we need the one that connects to the pins of the +12 V block. In the photo, this resistor is marked with red varnish.

This resistor must be unsoldered from the board and its resistance measured. In our case it is 38.5 kOhm.

Instead, you need to solder a variable resistor, which you first set to the same resistance of 38.5 kOhm.

By gradually increasing the resistance of the variable resistor, we achieve an output voltage of 14.4 V.

Attention! For each power supply, the value of this resistor will be different, because The circuits and details in the blocks are different, but the algorithm for changing the voltage is the same for everyone. When the voltage rises above 15 V, PWM generation may be disrupted. After this, the unit will have to be rebooted, after first reducing the resistance of the variable resistor.

In our unit, it was not possible to immediately increase the voltage to 14 V, the resistance of the variable resistor was not enough, so we had to add another constant one in series with it.

When the voltage of 14.4 V is reached, you can safely remove the variable resistor and measure its resistance (it was 120.8 kOhm).

In the resistor measurement field, it is necessary to select a constant resistor with as close a resistance as possible.

We made it up from two 100 kOhm and 22 kOhm.

We are testing the work.

At this stage, you can safely close the lid and use the charger. But if you wish, you can connect a digital voltammeter to this unit, this will give us the opportunity to monitor the charging progress.

You can also screw on the handle for easy carrying and cut a hole in the lid for a digital device.

The final test, we make sure that everything is assembled correctly and works well.

Attention! This charger retains the function of short circuit and overload protection. But it does not protect against overturning! Under no circumstances should you connect the battery to the charger with the wrong polarity; the charger will instantly fail.

When converting a power supply into a charger, it is advisable to have a circuit diagram on hand. To make life easier for our readers, we have made a small selection of ATX computer power supply diagrams.

There are a lot of interesting schemes to protect against polarity reversal. One of them can be found in this article.

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A battery charger from a power supply is a useful and inexpensive device in half an hour

To recharge the battery, the best option is a ready-made charger (charger). But you can do it yourself. There are many different ways to assemble a homemade charger: from the simplest circuits using a transformer, to pulse circuits with adjustable capabilities. The medium in complexity of implementation is the memory from a computer power supply. The article describes how to make a charger from a computer power supply for a car battery with your own hands.

Homemade charger from a power supply

Converting a computer power supply into a charger is not difficult, but you need to know the basic requirements for chargers designed to charge car batteries. For a car battery, the charger must have the following characteristics: the maximum voltage supplied to the battery must be 14.4 V, the maximum current depends on the charger itself. These are the conditions that are created in the electrical system of a car when the battery is recharged from a generator (video author Rinat Pak).

Tools and materials

Taking into account the requirements described above, to make a charger with your own hands, you first need to find a suitable power supply. A used ATX in working condition with a power of 200 to 250 W is suitable.

We take as a basis a computer that has the following characteristics:

• output voltage 12V;
• rated voltage 110/220 V;
• power 230 W;
• the maximum current value is not more than 8 A.

Tools and materials you will need:

• soldering iron and solder;
• screwdriver;
• 2.7 kOhm resistor;
• 200 Ohm and 2 W resistor;
• 68 Ohm resistor and 0.5 W;
• resistor 0.47 Ohm and 1 W;
• resistor 1 kOhm and 0.5 W;
• two 25 V capacitors;
• 12V automotive relay;
• three 1N4007 diodes 1 A;
• silicone sealant;
• green LED;
• voltammeter;
• "crocodiles";
• flexible copper wires 1 meter long.

Having prepared all the necessary tools and spare parts, you can begin to manufacture a charger for the battery from the computer power supply.

Algorithm of actions

The battery should be charged under voltage in the range of 13.9-14.4 V. All computers operate with a voltage of 12V. Therefore, the main task of the modification is to raise the voltage coming from the power supply to 14.4 V. The main modification will be carried out with the PWM operating mode. The TL494 chip is used for this. You can use a power supply with absolute analogues of this circuit. This circuit is used to generate pulses and also as a driver for a power transistor, which performs the function of protecting against high currents. To regulate the voltage at the output of the computer power supply, the TL431 chip, which is installed on an additional board, is used.

Additional board with TL431 chip

There is also a resistor for tuning, which makes it possible to adjust the output voltage in a narrow range.

Work on remaking the power supply consists of the following stages:

1. To make modifications to the block, you first need to remove all unnecessary parts from it and unsolder the wires. What is superfluous in this case is the 220/110 V switch and the wires going to it. The wires should be unsoldered from the power supply. The unit requires a voltage of 220 V to operate. By removing the switch, we will eliminate the possibility of the unit burning out if the switch is accidentally switched to the 110 V position.
2. Next, we unsolder, bite off unnecessary wires, or use any other method to remove them. First, we find the blue 12V wire coming from the capacitor and solder it. There may be two wires, both need to be unsoldered. We only need a bunch of yellow wires with a 12 V output, leaving 4 pieces. We also need ground - these are black wires, we also leave 4 of them. In addition, you need to leave one green wire. The remaining wires are completely removed or soldered.
3. On the board along the yellow wire we find two capacitors in a circuit with a voltage of 12V, they usually have a voltage of 16V, they must be replaced with 25V capacitors. Over time, capacitors become unusable, so even if the old parts are still in working order, it is better to replace them.
4. At the next stage, we need to ensure that the unit operates every time it is connected to the network. The fact is that the power supply in a computer works only if the corresponding wires in the output bundle are short-circuited. In addition, overvoltage protection must be excluded. This protection is installed in order to disconnect the power supply from the electrical network if the output voltage supplied to it exceeds a specified limit. It is necessary to exclude the protection, since the computer is allowed a voltage of 12 V, and we need to get 14.4 V at the output. For the built-in protection, this will be considered overvoltage and it will turn off the unit.
5. The overvoltage shutdown action signal, as well as the on and off signals, pass through the same optocoupler. There are only three optocouplers on the board. With their help, communication is carried out between the low-voltage (output) and high-voltage (input) parts of the power supply. To prevent the protection from tripping during overvoltage, you need to close the contacts of the corresponding optocoupler with a solder jumper. Thanks to this, the unit will be on all the time if it is connected to the electrical network and will not depend on what voltage is at the output.

   Solder jumper in red circle

6. At the next stage, we need to achieve an outgoing voltage of 14.4 V when operating at idle, because the voltage on the power supply is initially 12 V. For this we need a TL431 chip, which is located on an additional board. Finding her won't be difficult. Thanks to the microcircuit, the voltage is regulated on all tracks that come from the power supply. The tuning resistor located on this board allows you to increase the voltage. But it allows you to increase the voltage value to 13 V, but it is impossible to get a value of 14.4 V.
7. It is necessary to replace the resistor that is connected to the network in series with the trimming resistor. We are replacing it with a similar one, but with lower resistance - 2.7 kOhm. This makes it possible to expand the output voltage setting range and obtain an output voltage of 14.4 V.
8. Next, you need to start removing the transistor, which is located near the TL431 chip. Its presence may affect the correct operation of the TL431, meaning it may prevent the output voltage from being maintained at the required level. In the red circle is the location where the transistor was located.

   Transistor location

9. Then, to obtain a stable output voltage at idle, it is necessary to increase the load on the power supply output through the channel, where the voltage was 12 V, but will become 14.4 V, and through the 5 V channel, but we do not use it. As a load for the first 12 V channel, a resistor with a resistance of 200 Ohms and a power of 2 W will be used, and the 5 V channel will be supplemented for the load with a resistor with a resistance of 68 Ohms and a power of 0.5 W. Once these resistors are installed, the no-load no-load output voltage can be adjusted to 14.4V.
10. Next you need to limit the output current. It is individual for each power supply. In our case, its value should not exceed 8 A. To achieve this, you need to increase the value of the resistor in the primary circuit of the winding of the power transformer, which is used as a sensor used to determine overload. To increase the value, the installed resistor must be replaced with a more powerful one with a resistance of 0.47 Ohms and a power of 1 W. After this replacement, the resistor will function as an overload sensor, so the output current will not exceed 10 A even if the output wires are shorted, simulating a short circuit.

    Resistor to replace

11. At the last stage, you need to add a circuit to protect the power supply from connecting the charger to the battery with the wrong polarity. This is the circuit that will really be created with your own hands and is not included in the computer power supply. To assemble the circuit, you will need a 12 V automotive relay with 4 terminals and 2 diodes rated for 1 A, for example, 1N4007 diodes. In addition, you need to connect a green LED. Thanks to the diode, it will be possible to determine the charging status. If it lights up, it means the battery is connected correctly and is charging. In addition to these parts, you also need to take a resistor with a resistance of 1 kOhm and a power of 0.5 W. The figure shows the protection circuit.

    Power supply protection circuit

12. The operating principle of the circuit is as follows. The battery with the correct polarity is connected to the output of the charger, that is, the power supply. The relay is activated due to the energy remaining in the battery. After the relay operates, the battery begins to charge from the assembled charger through the closed contact of the power supply relay. Charging confirmation will be indicated by a glowing LED.
13. To prevent overvoltage that occurs when the coil is turned off due to the electromotive force of self-induction, a 1N4007 diode is connected to the circuit in parallel with the relay. It is better to glue the relay to the power supply heatsink with silicone sealant. Silicone remains elastic after drying and is resistant to thermal stress, such as compression and expansion, heating and cooling. When the sealant dries, the remaining elements are attached to the relay contacts. Instead of sealant, bolts can be used as fasteners.

    Installation of the remaining elements

14. It is better to choose wires for the charger of different colors, for example, red and black. They should have a cross-section of 2.5 square meters. mm, be flexible, copper. The length must be at least a meter. The ends of the wires must be equipped with crocodiles and special clamps with which the charger is connected to the battery terminals. To secure the wires in the body of the assembled device, you need to drill appropriate holes in the radiator. You need to thread two nylon ties through them, which will hold the wires.

Ready charger

To control the charging current, you can also install an ammeter into the charger body. It must be connected in parallel to the power supply circuit. As a result, we have a charger that we can use to charge the car battery and more.

Conclusion

The advantage of this charger is that the battery will not be recharged when using the device and will not deteriorate, no matter how long it is connected to the charger.

The disadvantage of this charger is the absence of any indicators by which one could judge the state of charge of the battery.

It is difficult to determine whether the battery is charged or not. You can calculate the approximate charging time by using the readings on the ammeter and applying the formula: current in Amperes multiplied by time in hours. It was experimentally found that it takes 24 hours, that is, a day, to fully charge a conventional battery with a capacity of 55 A/h.

This charger retains the function of overload and short circuit. But if it is not protected from reverse polarity, you cannot connect the charger to a battery with the wrong polarity, the device will fail.

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Charger from a computer power supply

Hello everyone, today I will tell you how to make a charger for a car battery with your own hands from a computer power supply. So, we take the power supply and remove the top cover or simply disassemble it. We look for a chip on the board and look carefully at it, or rather at its designation, if you find a TL494 or KA7500 chip (or their analogues) there, then you are very lucky and we can You can easily remake this power supply without any additional hassles. We disassemble the power supply, take out the board and unsolder all the wires from it, we will no longer need them. To charge the battery normally, we should increase the output voltage of the power supply, since 12 volts for charging is not enough, we need about 14.4 volts.

We do this, take a tester and use it to find five volts that are suitable for the 13, 14 and 15 legs of the microcircuit and cut the trace, by doing this we turn off the power supply’s protection against voltage increases. And accordingly, when the block is connected to the network, it will turn on immediately. Next, we find 1 leg on the microcircuit, following this path we find 2 resistors and remove them, in my case these are resistors R2 and R1. In their places we solder variable resistors. One adjustable resistor with a handle is 33 Kom, and the second for a screwdriver is 68 Kom. Thus, we have achieved that we can now regulate the voltage at the output over a wide range.

It should look something like the photo. Next, we take a piece of wire, one and a half meters long and with a cross-section of 2.5 squares, we clean it from the sheath. Then we take two crocodiles and solder our wires to them. It is advisable to install a 10 amp fuse on the positive wire.

Now we find + 12 volts and ground on the board, and solder the wires to them. Next, connect the tester to the power supply. Set the variable resistor knob to the left position, using the second resistor (which is under the screwdriver), rotating it to set the lower voltage value to 14.4 volts. Now, by rotating the variable resistor, we can see how our voltage rises, but now it will not drop below 14.4 volts. This completes the block setup.

We begin assembling the power supply. We screw the board into place. For beauty, I installed LED lighting inside. If you install an LED strip like I did, don’t forget to solder a 22 Ohm resistor in series with it, otherwise it will burn out. Also install a 22 Ohm resistor on the fan in the gap of any wire.

I installed a variable resistor on a PCB plate and brought it out. It is needed to adjust the strength of the output current by increasing the voltage at the output; in short, the larger the battery capacity, the more we turn the knob to the right. When I assembled everything, I secured the wires with hot glue. This is how the charger turned out. Now you will not have problems charging the battery.

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Car charger from computer power supply

The power supply of a personal computer can be converted into a car charger without much difficulty. It provides the same voltage and current as when recharging from the car’s standard electrical outlet. The circuit is devoid of homemade printed circuit boards and is based on the concept of maximum ease of modification.

The basis was taken from a personal computer power supply with the following characteristics:

Rated voltage 220/110 V; - output voltage 12 V; - power 230 W;

The maximum current is no more than 8 A.

So, first you need to remove all unnecessary parts from the power supply. They are a 220 / 110 V switch with wires. This will prevent the device from burning out if the switch is accidentally switched to the 110 V position. Then you need to get rid of all the outgoing wires, with the exception of a bundle of 4 black and 2 yellow wires (they are responsible for powering the device).

Next, you should achieve a result where the power supply will always work when connected to the network, and also eliminate overvoltage protection. The protection turns off the power supply if the outgoing voltage exceeds a certain specified value. This needs to be done because the voltage we need should be 14.4 V, instead of the standard 12.0 V.

The on/off signals and surge protection actions pass through one of three optocouplers. These optocouplers connect the low-voltage and high-voltage sides of the power supply. So, in order to achieve the desired result, we should close the contacts of the desired optocoupler using a solder jumper (see photo).

The next step is to set the output voltage to 14.4 V in idle mode. To do this, we are looking for a board with a TL431 chip. It acts as a voltage regulator on all outgoing tracks of the power supply. This board contains a trimming resistor that allows you to change the outgoing voltage in a small range.

The trim resistor may not have enough capabilities (since it allows you to increase the voltage to approximately 13 V). In this case, you need to replace the resistor connected in series with the trimmer with a resistor with lower resistance, namely 2.7 kOhm.

Then you should add a small load consisting of a resistor with a resistance of 200 Ohms and a power of 2 W to the output on the “12 V” channel and a resistor with a resistance of 68 Ohms, with a power of 0.5 W to the output on the “5 V” channel. In addition, you need to get rid of the transistor located next to the TL431 chip (see photo).

It was found that it prevents the voltage from stabilizing at the level we need. Only now, using the tuning resistor mentioned above, we set the output voltage to 14.4 V.

Next, in order for the output voltage to be more stable at idle, it is necessary to add a small load to the output of the unit along the +12 V channel (which we will have +14.4 V), and on the +5 V channel (which we do not use). A 200 Ohm 2 W resistor is used as a load on the +12 V channel (+14.4), and a 68 Ohm 0.5 W resistor is used on the +5 V channel (not visible in the photo, because it is located behind an additional board):

We also need to limit the current at the output of the device to 8-10 A. This current value is optimal for this power supply. To do this, you need to replace the resistor in the primary circuit of the power transformer winding with a more powerful one, namely 0.47 Ohm 1W.

This resistor acts as an overload sensor and the outgoing current will not exceed 10 A even if the output terminals are short-circuited.

The last step is to install a protection circuit to prevent the charger from being connected to the battery with the wrong polarity. To assemble this circuit, we will need a car relay with four terminals, 2 1N4007 diodes (or similar) as well as a 1 kOhm resistor and a green LED, which will indicate that the battery is connected correctly and is charging. The protection circuit is shown in the figure.

The scheme works on this principle. When the battery is correctly connected to the charger, the relay is activated and closes the contact using the energy remaining in the battery. The battery is charged from the charger, which is indicated by the LED. To prevent overvoltage from the self-induced emf that occurs on the relay coil when it is turned off, a 1N4007 diode is connected in parallel with the relay.

The relay with all elements is mounted to the charger radiator using bolts or silicone sealant.

The wires that are used to connect the charger to the battery must be flexible copper, multi-colored (for example, red and blue) with a cross-section of at least 2.5 mm? and about 1 meter long. It is necessary to solder crocodiles to them for convenient connection to the battery terminals.

I would also advise installing an ammeter into the charger body to monitor the charging current. It must be connected in parallel to the circuit “from the power supply”.

The device is ready.

The advantages of such a charger include the fact that when using it, the battery will not be recharged. The disadvantages are the lack of indication of the battery charge level. But to calculate the approximate battery charging time, you can use the data from the ammeter (current “A” * time “h”). In practice, it was found that within a day a battery with a capacity of 60 Ah can be charged 100%.

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Charger from power supply from computer

It all started with the fact that they gave me an ATX power supply from a computer. So it sat in the stash for a couple of years until the need arose to build a compact battery charger. The unit is made on the TL494 chip, well known for the series of power supplies, which makes it possible to easily convert it into a charger. I will not go into details of the operation of the power supply, the modification algorithm is as follows:

1. Clean the power supply from dust. You can use a vacuum cleaner, you can blow it with a compressor, whatever you have at hand. 2. We check its performance. To do this, in the wide connector that goes to the computer motherboard, you need to find the green wire and jump it to minus (black wire), then turn on the power supply and check the output voltages. If the voltage (+5V, +12V) is normal, proceed to step 3.

3. Disconnect the power supply from the network and remove the printed circuit board. 4. Solder off the excess wires, solder a jumper on the green wire and the negative wire on the board. 5. We find a TL494 chip on it, maybe an analogue of the KA7500.

TL494 We unsolder all the elements from pins of the microcircuit No. 1, 4, 13, 14, 15, 16. A resistor and capacitor should remain on pins 2 and 3, we also solder everything else. Often 15-14 legs of the microcircuit are located together on one track, they need to be cut. You can cut the extra tracks with a knife, this will better eliminate installation errors.

Refinement scheme...

Resistor R12 can be made with a piece of thick copper wire, but it is better to take a set of 10 W resistors connected in parallel or a shunt from a multimeter. If you install an ammeter, you can solder it to the shunt. It should be noted here that the wire from the 16th leg should be on the minus load of the power supply, and not on the total mass of the power supply! The correct operation of the current protection depends on this.

7. After installation, we connect an incandescent light bulb, 40-75 W 220V, in series to the unit via the power supply. This is necessary so as not to burn the output transistors if there is an installation error. And we turn on the block to the network. When you turn it on for the first time, the light should blink and go out, and the fan should work. If everything is fine, go to step 8.

8. Using a variable resistor R10, we set the output voltage to 14.6 V. Next, we connect a 12 V, 55 W car light bulb to the output and set the current so that the unit does not turn off when connecting a load of up to 5 A, and turns off when a load is more than 5 A. Current value may be different, depending on the dimensions of the pulse transformer, output transistors, etc... On average, 5 A will be used for a charger.

9. Solder the terminals and go to test the battery. As the battery charges, the charge current should decrease and the voltage should be more or less stable. The end of the charge will be when the current decreases to zero.

How to remove true key program from computer

A car charger or an adjustable laboratory power supply with an output voltage of 4 - 25 V and a current of up to 12A can be made from an unnecessary computer AT or ATX power supply.

Let's look at several scheme options below:

Options

From a computer power supply with a power of 200W, you can actually get 10 - 12A.

AT power supply circuit for TL494

Several ATX power supply circuits for TL494

Rework

The main modification is as follows: we unsolder all the extra wires coming from the power supply to the connectors, leave only 4 pieces of yellow +12V and 4 pieces of black housing, twist them into bundles. We find on the board a microcircuit with number 494, in front of the number there may be different letters DBL 494, TL 494, as well as analogues MB3759, KA7500 and others with a similar connection circuit. We are looking for a resistor going from the 1st leg of this microcircuit to +5 V (this is where the red wire harness was) and remove it.

For an regulated (4V - 25V) power supply, R1 should be 1k. Also, for the power supply, it is desirable to increase the capacity of the electrolyte at the 12V output (for a charger it is better to exclude this electrolyte), make several turns on a ferrite ring with a yellow beam (+12V) (2000NM, 25 mm in diameter is not critical).

It should also be borne in mind that on the 12 volt rectifier there is a diode assembly (or 2 back-to-back diodes) rated for a current of up to 3 A, it should be replaced with the one on the 5 volt rectifier, it is rated up to 10 A, 40 V , it is better to install the BYV42E-200 diode assembly (Schottky diode assembly Ipr = 30 A, V = 200 V), or 2 back-to-back powerful diodes KD2999 or similar ones in the table below.

If you need to connect the soft-on pin to the common wire to start the ATX power supply (the green wire goes to the connector). The fan needs to be turned 180 degrees so that it blows inside the unit, if you are using it as a power supply, it is better to power the fan with the 12th the legs of the microcircuit through a 100 Ohm resistor.

It is advisable to make the case from dielectric, not forgetting about the ventilation holes; there should be enough of them. Original metal case, use at your own risk.

It happens that when you turn on the power supply at a high current, the protection may work, although for me it doesn’t work at 9A, if anyone encounters this, you should delay the load when turning it on for a couple of seconds.

Another interesting option for redesigning a computer power supply.

In this circuit, voltage (from 1 to 30 V) and current (from 0.1 to 10A) are adjusted.

Voltage and current indicators are well suited for a homemade unit. You can buy them on the Trowel website.

P O P U L A R N O E:

On New Year's Eve, many radio amateurs are concerned with the question: how to “revive” the New Year’s beauty? Below, we offer several options for switches for Christmas tree garlands (or ordinary decorated lamps), varying in degree of complexity and implemented lighting effects. These devices can be used not only for the New Year, they are also suitable for decorating a room during holidays and dances.

What is a radio receiver? A radio receiver is a device for receiving electromagnetic waves with subsequent conversion (demodulation) of the information contained in them, which can then be used.

Circuits for radio receivers on microcircuits look more attractive - they are easier to manufacture compared to circuits on transistors and have better technical characteristics.

Below are the diagrams of simple AM ​​radio receivers on microcircuits: TDA1072, TL071, T081, LM1863, AN7002K.

There are times when, when copying files to removable media, an error appears: “The disk is write-protected, remove the protection.”

The reasons for blocking a flash drive can be different, for example:

• The physical switch is in the wrong position;
• Media failure. For example, you cannot remove the media until the process (writing, renaming, moving or reading) has completed;
• Incorrect Windows settings, for example, a software ban installed in the operating system;
• The host is infected with a virus;
• Malfunction of computer USB ports;
• Lack of required driver.

Let's look at the main options for fixing this problem.

A rechargeable battery is a device that wears out and is discharged during operation. To charge the battery, a special device is used, which you can buy or make yourself. We will tell you below how to build a charger for a car battery from a computer and laptop power supply.

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How to charge a battery from a computer power supply?

The cost of high-quality chargers is high. Therefore, many car owners decide to convert the ATX power supply from a stationary PC into a charger. This procedure is not particularly complicated, but before you begin the task and convert the power supply to a charger that can charge a car battery, you should understand the requirements for the charger. In particular, the maximum voltage level supplied to the battery should be no more than 14.4 volts to prevent rapid battery wear.

User Vetal in his video showed how you can convert a power supply into a charger.

Getting ready to complete the task

To build a homemade charger from a computer power supply for 200W, 300W or 350W (PWM 3528), you will need the following materials and tools:

• crocodile clips for connecting to the battery;
• a resistor element of 2.7 kOhm, as well as 1 kOhm and 0.5 W;
• soldering iron with tin and rosin;
• two screwdrivers (Phillips and flat head);
• resistor elements of 200 Ohm and 2 W, as well as 68 Ohm and 0.5 W;
• regular 12V machine relay;
• two 25V capacitor elements;
• three 1N4007 diodes for 1 ampere;
• LED element (any color, but green is better);
• silicone sealant;
• voltammeter;
• two flexible copper wires (1 meter each).

You will also need the power supply itself, which must have the following characteristics:

• output voltage - 12 volts;
• rated voltage parameter - 110/220 V;
• power value - 230 W;
• maximum current parameter - no higher than 8 amperes.

Step-by-step instruction

The procedure for charging a machine battery is carried out under voltage, the value of which is from 13.9 to 14.4 volts. All stationary units operate with a voltage of 220 V, so the primary task is to reduce the operating parameter to 14.4 V. The charging device is based on a TL494 (7500) microcircuit; if it is not available, an analogue can be used. The microcircuit is needed to generate signals and is used as a driver of a transistor element designed to protect the device from increased current. On the additional power supply board there is another circuit - TL431 or another, similar, designed to adjust the output voltage parameter. There is also a resistor element for adjustment, with which you can adjust the output voltage in a narrow range.

Learn more about how to convert a computer power supply into a charger for a car battery from the video published by the Soldering Iron TV channel.

To convert a power supply from a computer into a car charger with your own hands, read the diagram and follow the instructions:

1. First, you need to remove all unnecessary components and elements from the ATX computer power supply, after which the cables are unsoldered from it. Use a soldering iron to avoid damaging the contacts. It is necessary to remove the 220/110 volt switch with the cables connected to it. By removing the switch, you can prevent the possibility of the PSU from burning out if you accidentally switch it to 110V.
2. Then unnecessary cables are unsoldered from the device and removed. Remove the blue wire connected to the capacitor element and use a soldering iron. In some power supplies, two wires are connected to the capacitor; both should be removed. Also on the board you will see a bunch of yellow cables with a 12 volt output, there should be four of them, leave them all. There should also be four black wires here, they should also be left, since this is ground or ground. We need to leave one more green wire, all the others are removed.
3. Pay attention to the diagram. Using the yellow wiring, you can find two capacitor elements in a 12 volt circuit. Their operating voltage parameter is 16 V, so immediately remove them by desoldering and install two capacitors at 25 V. The capacitor elements swell and become inoperative. Even if they are intact and seem to be working, we recommend replacing them.
4. Now we need to complete the task so that the power supply is automatically activated every time it is plugged into a household network. The bottom line is that when the power supply is installed in a computer, it is activated if certain contacts at the output are closed. The surge protection needs to be removed. This element is designed to automatically disconnect the computer's power supply from the household network in case of overvoltage. It must be removed, because for optimal operation of the PC, 12 volts are required, and for the charger to function, 14.4 V is needed. The protection installed in the unit will perceive 14.4 volts as a voltage surge, as a result of which the charger will turn off and will not be able to charge the battery car.
5. Two pulses pass to the optocoupler on the board - actions from protection against voltage surges, shutdown, as well as activation and deactivation. There are a total of three optocouplers in the circuit. Thanks to these elements, communication is carried out between the input and output components of the block. These parts are called high voltage and low voltage. To prevent the protection from tripping during voltage surges, you should close the contacts of the optocoupler; this can be done using a jumper made of solder. This action will ensure uninterrupted operation of the power supply when it is connected to a household network.
6. Now we need to ensure that the outgoing voltage is 14.4 volts. To complete the task, you will need a TL431 board installed on an additional circuit. Thanks to this component, the voltage is adjusted on all channels coming from the device. To increase the operating parameter, you will need a tuning resistor element located on the same circuit. With it, you can increase the voltage to 13 volts, but this is not enough for optimal operation of the charger. Therefore, the resistor connected in series with the trimming component must be replaced. It should be removed and replaced with a similar part, the resistance of which should be below 2.7 kOhm. This will increase the range of adjustment of the output parameter and obtain the required 14.4 volts.
7. Remove the transistor element installed next to the TL431 board. This part may negatively affect the functionality of the circuit. The transistor will prevent the device from maintaining the desired output voltage. In the photo below you will see the element, it is marked in red.
8. In order for the device for charging the battery to have a stable output voltage, it is necessary to increase the operating parameter of the load along the channel where the voltage of 12 volts passed. There is an additional 5 volt channel, but it is not necessary to use it. To provide the load, you will need a resistor component, the operating resistance value of which will be 200 Ohms, and the power will be 2 W. A 68 Ohm part is installed on the additional channel, the power value of which is 0.5 W. Once the resistor elements are soldered, you can adjust the output voltage to 14.4 volts without requiring a load.
9. The output current should then be limited. This parameter is individual for any power supply. Our current value should be no more than 8 amperes. To achieve this, it will be necessary to increase the rating of the resistor component installed in the primary winding circuit, adjacent to the transformer device. The latter is used as a sensor designed to determine the overload value. To increase the nominal value, the resistor must be replaced; instead, a component with a resistance of 0.47 Ohms is mounted, and the power value will be 1 W. The resistor is carefully soldered off and a new one is soldered in its place. After completing this task, the part will be used as a sensor, so the output current will be no more than 10 amperes, even if a short circuit occurs.
10. To ensure protection of the machine battery from incorrect polarity when connecting a homemade charging device, an additional circuit is installed in the device. We are talking about a board that you have to make yourself, since it is not included in the block itself. To develop it, you will need a prepared 12-volt relay, which should have four terminals. You will also need diode components with a current strength of 1 ampere. Alternatively, parts 1N4007 can be used. The circuit must be supplemented with an LED, which will indicate the status of the charging process. If the light is on, then the car battery is connected to the charger correctly. In addition to these components, you will need a resistor element whose operating resistance will be 1 kOhm and power 0.5 W. The operating principle of the circuit is as follows. The battery is connected via cables to the output of a homemade charger. The relay is activated thanks to the energy remaining from the battery. After the element is triggered, the charging process from the charger begins, as evidenced by the activation of the diode light bulb.
11. When the coil is deactivated, a voltage surge occurs as a result of the electromotive force of self-induction. To prevent its negative impact on the operation of the charging device, two diode components must be added to the board in parallel. The relay is fixed to the power supply radiator device using sealant. Thanks to this material, it is possible to ensure elasticity, as well as immunity of parts to thermal loads. We are talking about compression and expansion, heating and cooling. When the glue has dried, the remaining components must be connected to the relay contacts. If there is no sealant, ordinary bolts are suitable for fixation.
12. At the last stage, wires with “crocodiles” are connected to the block. It is better to use cables of different colors, for example, black and red or red and blue. This will prevent polarity confusion. The length of the wire will be at least one meter, and their cross-section should be 2.5 mm2. Clamps are connected to the ends of the cables, designed for fixing to the battery terminals. To fix the wires on the body of a homemade charging device, two holes of the appropriate diameter are drilled in the radiator device. Two nylon ties are threaded through the resulting holes, with the help of which the cables will be fixed. An ammeter can be installed in the charger; it will allow you to control the current level. The device is connected in parallel to the power supply circuit.
13. All that remains is to test the performance of the self-assembled memory.

1. The jumper on the diagram is marked in red 2. Transistor element on the board that needs to be removed 3. Resistor element in the primary circuit to be replaced 4. Scheme for assembling a board designed to protect the power supply in case of polarity violation

Charger from laptop power supply

You can build a charging device from a laptop power supply.

You cannot connect the power supply directly to the battery terminals.

The output voltage varies around 19 volts, and the current value is about 6 amperes. These parameters are enough to charge the battery, but the voltage is too high. There are two ways to solve the problem.

Without reworking the power supply

You will need to connect the so-called ballast in the form of a powerful optical lamp in series with the car’s battery. The light source will be used as a current limiter. A simple and affordable option. One contact of the lamp is connected to the positive output of the laptop power supply, and its second contact is connected to the positive of the battery. The negative from the power supply is connected directly to the negative terminal of the battery via a wire. After this, the power supply can be connected to a household network. The method is very simple, but there is a possibility of failure of the lighting source. This will cause both the battery and the unit to fail.

With modification of the power supply

You will need to lower the power supply voltage parameter so that the output voltage is about 14-14.5 V.

Let's look at the process of manufacturing and assembling a charging device using the example of a power supply from a Great Wall laptop:

1. First you need to disassemble the power supply housing. When disassembling, do not damage it, as it will be used for further use. The board, which is located inside, can be connected to a voltmeter to find out exactly what its operating voltage is. In our case it is 19.2 volts. A board built on TEA1751+TEA1761 chips is used.
2. The task of reducing the voltage is being performed. To do this, you will need to find a resistor element located at the output. We need a part that connects the sixth pin of the TEA1761 circuit to the positive terminal of the power supply. This resistor element should be desoldered using a soldering iron and its resistance should be measured. The operating parameter is 18 kOhm.
3. Instead of the dismantled element, a 22 kOhm trimmer resistor component is installed, but before soldering it should be set to 18 kOhm. Carefully solder the part so as not to damage other elements of the circuit.
4. Gradually lowering the resistance value, it is necessary to ensure that the output voltage parameter is 14-14.5 volts.
5. When you get the optimal voltage for charging the car battery, the soldered resistor can be unsoldered. Its resistance parameter is measured, in our case it is 12.37 kOhm. A constant resistor is selected based on this value or one close to it. We use two resistors of 10 kOhm and 2.6 kOhm. The ends of both parts are installed in a thermal chamber, after which they are soldered into the board.
6. We recommend testing the resulting circuit before assembling the device. The output voltage will be 14.25 volts, which is enough to charge the battery.
7. Let's start assembling the device. Connect the wires with clamps. Before soldering them, make sure that the polarity is maintained at the output. Depending on the laptop unit, the negative contact can be made in the form of a central wire, and the positive contact can be made in the form of a braid.
8. As a result, you get a device that can properly charge the battery. The amount of current during charging varies around 2-3 amperes. If this parameter drops to 0.2-0.5 amperes, then the charging procedure can be considered complete. For more convenient use, the charger is equipped with an ammeter, fixing it on the case. You can use an LED lamp that will tell the car owner that the charging process is complete.

The kt819a channel provided a video in which a charger made from a laptop PSU is examined in detail.

How to properly charge a battery with a homemade charger?

In order to prevent rapid battery failure, it is necessary to take into account certain nuances regarding proper recharging.

1. First, disconnect the battery terminals from the clamps. Remove the bolts that secure the battery retaining bar.
2. Remove the device from its mounting location and take it home or to the garage.
3. Clean the housing from dirt. Pay attention to the terminals themselves. If they have oxidation, they should be cleaned. Use a toothbrush or a construction brush; fine-grit sandpaper will do. The main thing is not to clean off the work plaque.
4. If the battery is serviceable, open all its cans and check the electrolyte level in them. The working solution must cover all sections. If this is not the case, then charging the battery may cause the boiling liquid to evaporate quickly, which will affect the functionality of the battery and its overall health. If necessary, add distilled water to the jars. Visually inspect the battery case for defects; sometimes fluid leakage is associated with cracks. If the damage is serious, the battery must be replaced.
5. Connect the clamps of the homemade charger to the battery terminals, observing the polarity. After this, the device can be connected to a household network. There is no need to unscrew the caps on the cans.
6. When the charging procedure is completed, check the electrolyte level and if everything is fine, tighten the cans. Install the battery in the car and make sure it is in working order.

Conclusion

The main advantage of the device is that the car battery will not be able to recharge during the charging process. If you forget to disconnect the battery from the charger, this will not affect its service life and will not lead to rapid wear. If you don't equip your charger with an LED indicator, you won't be able to tell whether the battery is charged or not.. Alternatively, you can approximately calculate the recharging time using the readings given by an ammeter connected to the charger. You can calculate it using the formula: the current value is multiplied by the charging time in hours. In practice, it takes about a day to complete the recharging task, provided that the battery capacity is 55 A/h. If you want to clearly see the charge level, then you can add dial or digital indicators to the device.

Computers cannot work without electricity. To charge them, special devices called power supplies are used. They receive AC voltage from the mains and convert it to DC. The devices can deliver enormous amounts of power in a small form factor and have built-in overload protection. Their output parameters are incredibly stable, and DC quality is ensured even under high loads. When you have an extra device like this, it makes sense to use it for many household tasks, for example, by converting it from a computer power supply into a charger.

The block has the shape of a metal box with a width of 150 mm x 86 mm x 140 mm. As standard, it is mounted inside the PC case using four screws, a switch and a socket. This design allows air to flow into the cooling fan of the power supply unit (PSU). In some cases, a voltage selector switch is installed to allow the user to select the readings. For example, in the United States there is an internal power supply that operates at a nominal voltage of 120 volts.

A computer's power supply consists of several components inside: a coil, capacitors, an electronic board for regulating current, and a fan for cooling. The latter is the main cause of failure for power supplies (PS), which must be taken into account when installing a charger from an atx computer power supply.

Types of power supply for a personal computer

IPs have a certain power, indicated in watts. A standard unit is typically capable of delivering around 350 watts. The more components installed on a computer: hard drives, CD/DVD drives, tape drives, fans, the more energy is required from the power supply.

Experts recommend using a power supply that provides more power than the computer requires, as it will operate in a constant "underload" mode, which will increase the life of the machine due to the reduced thermal impact on its internal components.

There are 3 types of IP:

1. AT Power Supply - used on very old PCs.
2. ATX power supply - still used on some PCs.
3. ATX-2 power supply - commonly used today.

Power supply parameters that can be used when creating a charger from a computer power supply:

1. AT / ATX / ATX-2:+3.3 V.
2. ATX / ATX-2:+5 V.
3. AT / ATX / ATX-2: -5 V.
4. AT / ATX / ATX-2: +5 V.
5. ATX / ATX-2: +12 V.
6. AT / ATX / ATX-2: -12 V.

Motherboard connectors

The IP has many different power connectors. They are designed in such a way that there is no mistake when installing them. To make a charger from a computer power supply, the user will not have to spend a lot of time choosing the right cable, since it simply won’t fit in the connector.

Types of connectors:

1. P1 (PC/ATX connector). The main job of a power supply unit (PSU) is to provide power to the motherboard. This is done via a 20-pin or 24-pin connector. The 24-pin cable is compatible with 20-pin motherboard.
2. P4 (EPS socket): Previously, the motherboard pins were insufficient to support the processor power. With GPU overclocking reaching 200W, the ability to provide power directly to the CPU was created. Currently this is P4 or EPS which provides sufficient processor power. Therefore, converting the computer power supply into a charger is economically justified.
3. PCI-E connector (6-pin 6+2). The motherboard can provide a maximum of 75W through the PCI-E interface slot. A faster dedicated graphics card requires much more power. To solve this problem, the PCI-E connector was introduced.

Cheap motherboards are equipped with a 4-pin connector. More expensive "overclocking" motherboards have 8-pin connectors. Additional ones provide excess processor power during overclocking.

Most power supplies come with two cables: 4-pin and 8-pin. Only one of these cables needs to be used. It is also possible to split the 8-pin cable into two segments to ensure backward compatibility with cheaper motherboards.

The left 2 pins of the 8-pin connector (6+2) on the right are disconnected to ensure backward compatibility with 6-pin graphics cards. The 6-pin PCI-E connector can supply an additional 75W per cable. If the graphics card contains a single 6-pin connector, it can be up to 150W (75W from motherboard + 75W from cable).

More expensive graphics cards require an 8-pin (6+2) PCI-E connector. With 8 pins, this connector can provide up to 150W per cable. A graphics card with a single 8-pin connector can handle up to 225W (75W from motherboard + 150W from cable).

Molex, a 4-pin peripheral connector, is used when creating a charger from a computer's power supply. These pins are very long lasting and can supply 5V (red) or 12V (yellow) to peripheral devices. In the past, these connections were often used to connect hard drives, CD-ROM players, etc.

Even GeForce 7800 GS video cards are equipped with Molex. However, their power consumption is limited, so nowadays most of them have been replaced by PCI-E cables and all that remains are powered fans.

Accessory connector

The SATA connector is a modern replacement for the outdated Molex. All modern DVD players, hard drives and SSDs run on SATA power. The Mini-Molex/Floppy connector is completely obsolete, but some PSUs still come with a mini-molex connector. These were used to power floppy drives with up to 1.44 MB of data. They have mostly been replaced by USB storage today.

Molex-PCI-E 6-pin adapter for powering the video card.

When using a 2x-Molex-1x PCI-E 6-pin adapter, you must first make sure that both Molexes are connected to different cable voltages. This reduces the risk of overloading the power supply. With the introduction of ATX12 V2.0, changes were made to the 24-pin system. The older ATX12V (1.0, 1.2, 1.2 and 1.3) used a 20-pin connector.

There are 12 versions of the ATX standard, but they are so similar that the user does not need to worry about compatibility when installing a charger from the computer's power supply. To ensure this, most modern sources allow you to disconnect the last 4 pins of the main connector. It is also possible to create advanced compatibility using an adapter.

Computer supply voltage

A computer requires three types of DC voltage. 12 volts is needed to supply voltage to the motherboard, graphics cards, fans, and processor. The USB ports require 5 volts, while the CPU itself uses 3.3 volts. 12 volts are also applicable for some smart fans. The electronic board in the power supply is responsible for sending converted electricity through special cable sets to power devices inside the computer. Using the above components, AC voltage is converted into pure DC current.

Almost half of the work done by a power supply is done with capacitors. They store energy that will be used for continuous work flow. When making a computer power supply, the user must be careful. Even if the computer is turned off, there is a chance that electricity will be stored inside the power supply in capacitors, even several days after the shutdown.

Cable kit color codes

Inside the power supplies, the user sees many cable sets coming out with different connectors and different numbers. Power cable color codes:

1. Black, used to provide current. Every other color must be connected to the black wire.
2. Yellow: +12V.
3. Red: +5V.
4. Blue: -12V.
5. White: -5V.
6. Orange: 3.3V.
7. Green, control wire for checking DC voltage.
8. Purple: +5V standby.

The output voltages of a computer's power supply can be measured using a proper multimeter. But due to the higher risk of short circuit, the user should always connect the black cable with the black one on the multimeter.

Power cord plug

The hard drive wire (whether it is IDE or SATA) has four wires attached to the connector: a yellow one, two black ones in a row, and a red one. The hard drive uses both 12V and 5V at the same time. 12V powers the moving mechanical parts, while 5V powers the electronic circuits. So all these cable kits are equipped with 12V and 5V cables at the same time.

The electrical connectors on the motherboard for processors or chassis fans have four legs that support the motherboard for 12V or 5V fans. Apart from black, yellow and red, other colored wires can only be seen in the main connector, which goes directly into the motherboard socket. These are purple, white or orange cables that are not used by consumers to connect peripheral devices.

If you want to make a car charger from a computer power supply, you need to test it. You will need a paperclip and about two minutes of time. If you need to reconnect the power supply to the motherboard, you just need to remove the paperclip. There will be no changes in it from using a paper clip.

Procedure:

• Find the green wire in the cable tree from the power supply.
• Follow it to a 20 or 24 pin ATX connector. The green wire is in a sense a “receiver”, which is needed to supply energy to the power supply. There are two black ground wires between it.
• Place the paperclip into the pin with the green wire.
• Place the other end into one of the two black ground wires next to the green one. It doesn't matter which one will work.

Although the paperclip will not produce a large shock, it is not recommended to touch the metal part of the paperclip while it is energized. If you need to leave a paperclip indefinitely, you need to wrap it with electrical tape.

If you start making a charger with your own hands from a computer power supply, take care of the safety of your work. The source of the threat is capacitors, which carry a residual charge of electricity that can cause significant pain and burns. Therefore, you need to not only make sure that the power supply is securely disconnected, but also wear insulating gloves.

After opening the power supply, they assess the workspace and make sure that there will be no problems with clearing the wires.

They first think through the design of the source, measuring with a pencil where the holes will be in order to cut the wires of the required length.

Perform wire sorting. In this case, you will need: black, red, orange, yellow and green. The rest are redundant, so they can be cut off on the circuit board. Green indicates power on after standby. It is simply soldered to the black ground wire, which will ensure that the power supply is turned on without a computer. Next you need to connect the wires to 4 large clamps, one for each set of colors.

After this, you need to group the 4-wire colors together and cut them to the required length, strip the insulation and connect them at one end. Before drilling holes, you need to take care of the chassis circuit board so that it is not contaminated with metal shavings.

Most PSUs cannot completely remove the PCB from the chassis. In this case, it must be carefully wrapped in a plastic bag. Having finished drilling, you need to treat all rough spots and wipe the chassis with a cloth to remove debris and plaque. Then install the retaining posts using a small screwdriver and clamps, securing them with pliers. After this, close the power supply and mark the voltage on the panel with a marker.

Charging a car battery from an old PC

This device will help the car enthusiast in a difficult situation when he urgently needs to charge the car battery without having a standard device, but using only a regular PC power supply. Experts do not recommend constantly using a car charger from a computer power supply, since the voltage of 12 V is slightly below what is required when charging the battery. It should be 13 V, but it can be used as an emergency option. To increase the voltage where previously there was 12V, you need to change the resistor to 2.7 kOhm on the trimmer resistor installed on the additional power supply board.

Since power supplies have capacitors that store electricity for a long time, it is advisable to discharge them using a 60W incandescent lamp. To attach the lamp, use the two ends of the wire to connect to the cap terminals. The backlight will slowly go out, discharging the cover. Shorting the terminals is not recommended as this will cause a large spark and may damage the PCB traces.

The procedure for making a charger from a computer power supply with your own hands begins with removing the top panel of the power supply. If the top panel has a 120mm fan, disconnect the 2-pin connector from the PCB and remove the panel. You need to cut the output cables from the power supply using pliers. You shouldn’t throw them away; it’s better to reuse them for non-standard tasks. For each connecting post, leave no more than 4-5 cables. The rest can be trimmed on the PCB.

Wires of the same color are connected and secured using cable ties. The green cable is used to turn on the DC power supply. It is soldered to the GND terminals or connected to the black wire from the bundle. Next, measure the center of the holes on the top cover, where the fixing posts should be secured. You need to be especially careful if a fan is installed on the top panel, and the gap between the edge of the fan and the IP is small for the fixing pins. In this case, after marking the central points, you need to remove the fan.

After this, you need to attach the fixing posts to the top panel in the order: GND, +3.3 V, +5 V, +12 V. Using a wire stripper, the insulation of the cables of each bundle is removed, and the connections are soldered. Use a heat gun to heat the sleeves over the crimp connections, then insert the tabs into the connecting pins and tighten the second nut.

Next, you need to return the fan to its place, connect the 2-pin connector to the socket on the circuit board, insert the panel back into the device, which may require some effort due to the bundle of cables on the crossbars, and close it.

Charger for screwdriver

If the screwdriver has a voltage of 12V, then the user is lucky. It can make a power supply for the charger without much modification. You will need a used or new computer power supply. It has several voltages, but you need 12V. There are many wires of different colors. You will need yellow ones that output 12V. Before starting work, the user must make sure that the power source is disconnected from the power source and has no residual voltage in the capacitors.

Now you can start converting your computer's power supply into a charger. To do this, you need to connect the yellow wires to the connector. This will be the 12V output. Do the same for the black wires. These are the connectors into which the charger will be connected. In the block, 12V voltage is not primary, so a resistor is connected to the red 5V wire. Next you need to connect the gray and one black wire together. This is a signal that indicates energy supply. The color of this wire may vary, so you need to make sure it is the PS-ON signal. This should be written on the power supply sticker.

After turning on the switch, the power supply should start, the fan should rotate, and the light should light up. After checking the connectors with a multimeter, you need to make sure that the unit produces 12 V. If so, then the screwdriver charger from the computer power supply is functioning correctly.

In fact, there are many options for adapting the power supply to your own needs. Those who like to experiment are happy to share their experiences. Here are some good tips.

Users shouldn't be afraid to upgrade the unit's box: they can add LEDs, stickers, or anything else they need to upgrade it. When disassembling the wires, you need to make sure that you are using an ATX power supply. If it's an AT or older power supply, it will most likely have a different color scheme for the wires. If the user does not have information about these wires, he should not re-equip the unit, since the circuit may be assembled incorrectly, which will lead to an accident.

Some modern power supplies have a communication wire that must be connected to the power supply for it to work. The gray wire connects to the orange and the pink wire to the red. A high wattage power resistor may become hot. In this case, you need to use a radiator for cooling in the design.

When converting computer switching power supplies (hereinafter referred to as UPS) with a TL494 control chip into power supplies for powering transceivers, radio equipment and chargers for car batteries, a number of UPSs accumulated that were faulty and could not be repaired, were unstable, or had a control chip of a different type .

They also got around to the remaining power supplies, and after some experimentation they developed the technology for converting them into chargers (hereinafter referred to as chargers) for car batteries.
Also, after the release, emails began to arrive with various questions, like what and how, where to start.

Where to begin?

Before you begin the rework, you should carefully read the book, it provides a detailed description of the operation of the UPS with the TL494 control chip. It would also be a good idea to visit the sites and, where the issues of redesigning computer UPSs are discussed in detail. For those radio amateurs who could not find the specified book, we will try to explain “on the fingers” how to “tame” a UPS.
And so about everything in order.

And so let’s consider the case when the battery is not yet connected. The AC mains voltage is supplied through the thermistor TR1, mains fuse FU1, and noise suppression filter to the rectifier on the diode assembly VDS1. The rectified voltage is smoothed by a filter on capacitors C6, C7, and the output of the rectifier produces a voltage of + 310 V. This voltage is supplied to a voltage converter using powerful key transistors VT3, VT4 with a pulse power transformer Tr2.

Let’s immediately make a reservation that for our charger there are no resistors R26, R27, intended for slightly opening transistors VT3, VT4. The base-emitter junctions of transistors VT3, VT4 are shunted by circuits R21R22 and R24R25, respectively, as a result of which the transistors are closed, the converter does not work, and there is no output voltage.

When the battery is connected to the output terminals Cl1 and Cl2, the VD12 LED lights up, voltage is supplied through the VD6R16 chain to pin No. 12 to power the MC1 microcircuit and through the VD5R12 chain to the middle winding of the matching transformer Tr1 of the driver on transistors VT1, VT2. Control pulses from pins 8 and 11 of the MC1 chip are sent to the driver VT1, VT2, and through the matching transformer Tr1 to the base circuits of the power key transistors VT3, VT4, opening them one by one.

The alternating voltage from the secondary winding of the power transformer Tr2 of the + 12 V voltage generation channel is supplied to a full-wave rectifier based on an assembly of two VD11 Schottky diodes. The rectified voltage is smoothed out by the LC filter L1C16 and goes to the output terminals Cl1 and Cl2. The output of the rectifier also powers the standard fan M1, intended for cooling UPS parts, connected through a damping resistor R33 to reduce the rotation speed of the blades and fan noise.

The battery is connected through terminal Cl2 to the negative output of the UPS rectifier through resistor R17. When the charging current flows from the rectifier to the battery, a voltage drop is formed across resistor R17, which is supplied to pin No. 16 of one of the comparators of the MC1 chip. When the charging current exceeds the set level (by moving the charge current setting resistor R4), the MC1 microcircuit increases the pause between output pulses, reducing the current to the load and thereby stabilizing the battery charging current.

The output voltage stabilization circuit R14R15 is connected to pin No. 1 of the second comparator of the MC1 microcircuit, and is designed to limit its value (at + 14.2 - + 16 V) in the event of the battery being disconnected. When the output voltage increases above the set level, the MC1 microcircuit will increase the pause between output pulses, thereby stabilizing the output voltage.
Microammeter PA1, using switch SA1, is connected to different points of the UPS rectifier, and is used to measure the charging current and voltage on the battery.

As a PWM control regulator MC1, a microcircuit of the TL494 type or its analogues is used: IR3M02 (SHARP, Japan), µA494 (FAIRCHILD, USA), KA7500 (SAMSUNG, Korea), MV3759 (FUJITSU, Japan, KR1114EU4 (Russia).

Let's start the renovation!

We unsolder all the wires from the output connectors, leave five yellow wires (+12 V voltage generation channel) and five black wires (GND, case, ground), twist four wires of each color together and solder them, these ends will subsequently be soldered to output terminals of the memory.

Remove the 115/230V switch and sockets for connecting cords.
In place of the upper socket, we install a PA1 microammeter for 150 - 200 µA from cassette recorders, for example M68501, M476/1. The original scale has been removed and a homemade scale made using the FrontDesigner_3.0 program has been installed instead; scale files can be downloaded from the magazine’s website. We cover the place of the lower socket with tin measuring 45×25 mm and drill holes for the resistor R4 and the switch for the type of measurement SA1. On the rear panel of the case we install terminals Cl 1 and Cl 2.

Also, you need to pay attention to the size of the power transformer (on the board - the larger one), in our diagram (Fig. 5) this is Tr 2. The maximum power of the power supply depends on it. Its height should be at least 3 cm. There are power supplies with a transformer less than 2 cm high. The power of these is 75 W, even if it is written 200 W.

In the case of remaking an AT type UPS, remove resistors R26, R27 that slightly open the transistors of the key voltage converter VT3, VT4. In case of alteration of an ATX type UPS, we remove the parts of the duty converter from the board.

We solder all the parts except: noise suppression filter circuits, high-voltage rectifier VDS1, C6, C7, R18, R19, inverter on transistors VT3, VT4, their base circuits, diodes VD9, VD10, power transformer circuits Tr2, C8, C11, R28, driver on transistors VT3 or VT4, matching transformer Tr1, parts C12, R29, VD11, L1, output rectifier, according to the diagram (Fig. 5).

We should end up with a board that looks something like this (Fig. 6). Even if a microcircuit like DR-B2002, DR-B2003, DR-B2005, WT7514 or SG6105D is used as a control PWM regulator, it is easier to remove them and make them from scratch on TL494. We manufacture the A1 control unit in the form of a separate board (Fig. 7).

The standard diode assembly in the +12 V rectifier is designed for too low a current (6 - 12 A) - it is not advisable to use it, although it is quite acceptable for a charger. In its place, you can install a diode assembly from a 5-volt rectifier (it is designed for a higher current, but has a reverse voltage of only 40 V). Since in some cases the reverse voltage on the diodes in the +12 V rectifier reaches a value of 60 V! , it is better to install an assembly on Schottky diodes with a current of 2×30 A and a reverse voltage of at least 100 V, for example, 63CPQ100, 60CPQ150.

We replace the rectifier capacitors of the 12-volt circuit with an operating voltage of 25 V (16-volt ones often swelled).

The inductance of inductor L1 should be in the range of 60 - 80 µH, we must unsolder it and measure the inductance, we often came across specimens at 35 - 38 µH, with them the UPS operates unstable, buzzes when the load current increases more than 2 A. If the inductance is too high, more 100 μH, reverse voltage breakdown of the Schottky diode assembly may occur if it was taken from a 5-volt rectifier. To improve cooling of the +12 V rectifier winding and the ring core, remove unused windings for the -5 V, -12 V and +3.3 V rectifiers. You may have to wind several turns of wire to the remaining winding until the required inductance is obtained (Fig. 8).

If the key transistors VT3, VT4 were faulty, and the original ones cannot be purchased, then you can install more common transistors like MJE13009. Transistors VT3, VT4 are screwed to the radiator, usually through an insulating gasket. It is necessary to remove the transistors and, to increase thermal contact, coat the gasket on both sides with thermal conductive paste. Diodes VD1 - VD6 designed for a forward current of at least 0.1 A and a reverse voltage of at least 50 V, for example KD522, KD521, KD510.

We replace all electrolytic capacitors on the +12 V bus with a voltage of 25 V. During installation, it is also necessary to take into account that resistors R17 and R32 heat up during operation of the unit; they must be located closer to the fan and away from the wires.
The VD12 LED can be glued to the PA1 microammeter from above to illuminate its scale.

Setup

When setting up the memory, it is advisable to use an oscilloscope; it will allow you to see the pulses at the control points and will help us significantly save time. We check the installation for errors. We connect the rechargeable battery (hereinafter referred to as the battery) to the output terminals. First of all, we check the presence of generation at pin No. 5 of the MS sawtooth voltage generator (Fig. 9).

We check the presence of the indicated voltages according to the diagram (Fig. 5) at pins No. 2, No. 13 and No. 14 of the MC1 microcircuit. We set the resistor R14 slider to the position of maximum resistance, and check for the presence of pulses at the output of the MC1 microcircuit, at pins No. 8 and No. 11 (Fig. 10).

We also check the signal shape between pins No. 8 and No. 11 of MS1 (Fig. 11), on the oscillogram we see a pause between pulses; the lack of pulse symmetry may indicate a malfunction of the basic driver circuits on transistors VT1, VT2.

We check the shape of the pulses on the collectors of transistors VT1, VT2 (Fig. 12),

And also the shape of the pulses between the collectors of these transistors (Fig. 13).

The lack of pulse symmetry may indicate a malfunction of the transistors themselves VT1, VT2, diodes VD1, VD2, the base-emitter junction of transistors VT3, VT4 or their base circuits. Sometimes a breakdown of the base-emitter junction of transistor VT3 or VT4 leads to the failure of resistors R22, R25, the diode bridge VDS1, and only then to the blowing of fuse FU1.

According to the diagram, the left terminal of resistor R14 is connected to a reference voltage source of 16 V (why 16 V - to compensate for losses in the wires and in the internal resistance of a heavily sulfated battery, although 14.2 V is also possible). By reducing the resistance of resistor R14 until the pulses disappear at pins No. 8 and No. 11 of the MS, more precisely at this moment the pause becomes equal to the half-cycle of pulse repetition.

First start-up, testing

A correctly assembled, error-free device starts up immediately, but for safety reasons, instead of a mains fuse, we turn on a 220 V 100 W incandescent lamp; it will serve as a ballast resistor and in an emergency will save the UPS circuit parts from damage.

We set the resistor R4 to the position of minimum resistance, turn on the charger (charger) to the network, and the incandescent lamp should flash briefly and go out. When the charger operates at a minimum load current, the radiators of transistors VT3, VT4 and the diode assembly VD11 practically do not heat up. As the resistance of resistor R4 increases, the charging current begins to increase; at a certain level, the incandescent lamp will flash. Well, that's all, you can remove the llama and put fuse FU1 in place.

If you still decide to install a diode assembly from a 5-volt rectifier (we repeat that it can withstand current, but the reverse voltage is only 40 V), turn on the UPS to the network for one minute, and use resistor R4 to set the current to load 2 - 3 A, turn off the UPS. The radiator with the diode assembly should be warm, but under no circumstances hot. If it is hot, it means that this diode assembly in this UPS will not work for a long time and will definitely fail.

We check the charger at the maximum current into the load; for this it is convenient to use a device connected in parallel with the battery, which will prevent the battery from being damaged by long-term charges during the setup of the charger. To increase the maximum charging current, you can slightly increase the resistance of resistor R4, but you should not exceed the maximum power for which the UPS is designed.

By selecting the resistances of resistors R34 and R35, we set the measurement limits for the voltmeter and ammeter, respectively.

Photos

Installation of the assembled device is shown in (Fig. 14).

Now you can close the lid. The appearance of the charger is shown in (Fig. 15).