The power supply of a personal computer without much difficulty can be converted into a car charger. It provides the same voltage and current as when recharging from the car's standard electrical network. The scheme is devoid of homemade printed circuit boards and is based on the concept of maximum ease of improvement.
The power supply from a personal computer was taken as a basis with the following characteristics:
— rated voltage 220/110 V;
- output voltage 12 V;
- power 230 W;
- maximum current no more than 8 A.
So, for starters, you need to remove all unnecessary spare 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 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 the result when the power supply will always work when it is plugged in, and also eliminate overvoltage protection. Protection turns off the power supply if the outgoing voltage exceeds a certain specified value. We need to do this because the voltage we need should be 14.4 V, instead of the standard 12.0 V.
The enable/disable signals and surge protection actions are routed through one of the three optocouplers. These optocouplers link the low 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 with 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 performs the function of a voltage regulator on all outgoing tracks of the power supply. This board contains a trimmer resistor that allows you to change the output voltage in a small range.
The capabilities of the trimmer resistor may not be enough (because it allows you to raise the voltage to approximately 13 V). In this case, it is necessary to replace the resistor connected in series with the trimmer with a resistor with a lower resistance, namely 2.7 kOhm.
Then you should add a small load consisting of a 200 Ohm resistor with a power of 2 W to the output through the 12 V channel and a 68 Ohm resistor with a power of 0.5 W to the output through 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 trimmer resistor mentioned above, we set the output voltage at 14.4 V.
Further, 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 block through the +12 V channel (which we will have +14.4 V), and through the +5 V channel (which we do not use). A 200 Ohm 2 W resistor was used as a load on the +12 V (+14.4) channel, and a 68 Ohm 0.5 W resistor on the +5 V channel (not visible in the photo, because it is for an additional fee):
We also need to limit the current strength at the output of the device at the level of 8-10 A. This current strength value is optimal for this power supply. To do this, you need to replace the resistor in the primary winding circuit of the power transformer with a more powerful one, namely 0.47 Ohm 1W.
This resistor acts as an overload sensor and the outgoing current will not exceed 10A even if the output terminals are short-circuited.
The last step is to install the protection circuit from connecting the charger to the battery with the wrong polarity. To assemble this circuit, we need a car relay with four terminals, 2 diodes 1N4007 (or similar), as well as a 1 kΩ resistor and a green LED that will signal that the battery is connected correctly and is charging. The protection scheme is shown in the figure.
The scheme works in this way. When the battery is properly connected to the charger, the relay is activated and closes the contact due to the energy remaining in the battery. The battery is being charged by the charger, which is indicated by the LED. To prevent overvoltage from the EMF of self-induction that occurs on the relay coil when it is turned off, a 1N4007 diode is connected in parallel with the relay.
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. They need to solder crocodiles for easy connection to the battery terminals.
I would also advise you to mount an ammeter in the charger case to control 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 - the lack of indication of the degree of battery charge. But to calculate the approximate time to charge the battery, you can use the data from the ammeter (current "A" * time "h"). In practice, it was found that in a day a battery with a capacity of 60 Ah has time to charge 100%.
If you have an old computer power supply (ATX) at home, then you should not throw it away. After all, it can be used to make an excellent power supply for home or laboratory purposes. The refinement will be minimal and in the end you will get an almost universal power supply with a number of fixed voltages.
Computer power supplies have a large load capacity, high stabilization and short circuit protection.
WikiHow is a wiki, which means that many of our articles are written by multiple authors. When creating this article, 46 people worked on editing and improving it, including anonymously.
A computer power supply (hereinafter referred to as PSU) costs about $30, while a laboratory power supply can cost you $100 or even more! By modifying a cheap and often free ATX PSU that can be found in any unnecessary computer, you can make a good laboratory PSU yourself with good power, short circuit protection and a stabilized 5V output. On most PSUs, the other outputs are not stabilized.
Take an ATX PSU or disconnect it from a non-working computer.
Disconnect the cable from the power supply and turn off the switch on the rear panel (if any). Also, make sure you are not grounded so that the remaining current will not pass through you.
Remove the screws that secure the PSU to the computer case and pull it out.
Cut off the connectors (leave a few inches of wire on the connectors so you can use them for something else later).
Discharge the power supply by leaving it unplugged for a few days. Some people connect a resistor (10 ohms) between the black and red wires (power cord on the outside), however this ensures that only low voltage is discharged - which is not dangerous anyway! But high-voltage capacitors can remain charged, which, if current is maintained, can be potentially dangerous or even fatal.
Gather the necessary parts: screw terminals (terminals), an LED with a 330 ohm current-limiting resistor, a switch (optional), a 10 ohm resistor of 10 W or more (see Tips), and insulating heat shrink tubing.
Open the PSU by removing the screws connecting the top and bottom of the case.
Separate the wires by color. If you have wires not listed here (brown, etc.), see the Tips section. Color code for wires: Red = +5V, Black = ground (0V), White = -5V, Yellow = +12V, Blue = -12V, Orange = +3.3V, Purple = +5V reserve (not used), Gray = PG (output) and green = ON (must be shorted to (0V) to turn on the PSU).
Drill holes in the free space of the PSU case. First mark the centers of the holes with a nail using a hammer, drill holes with a drill or dremel, then enlarge the holes with a reamer until they are the right size for the connecting terminals. Also, drill holes for the switch and LED (optional).
Insert the terminals into the corresponding holes and fasten with nuts at the back.
Make all necessary connections.
Check that the connections are secure by gently pulling on the wires. Locate bare wires and insulate them to prevent short circuits. Use super glue to fix the LED in the hole. Replace the cover.
Connect the cable to the connector on the back of the PSU and plug it into a power outlet. Turn on the main switch on the PSU if you installed one. Check if the indicator lights up. You can check the operation of the PSU by connecting a 12 V bulb to different outputs; can also be checked with a voltmeter. Make sure there is no short circuit in any wire. Tidy up the external case of the power supply unit.
Hello dear ladies and gentlemen!
On this page, I will briefly tell you about how to convert the power supply of a personal computer into a charger for car (and not only) batteries with my own hands.
A charger for car batteries must have the following property: the maximum voltage supplied to the battery is no more than 14.4V, the maximum charging current is determined by the capabilities of the device itself. It is this method of charging that is implemented on board the car (from the generator) in the normal mode of operation of the car's electrical system.
However, unlike the materials from this article, I chose the concept of maximum simplicity of improvements without the use of self-made printed circuit boards, transistors and other "bells and whistles".
A friend gave me a power supply for rework, he himself found it somewhere at his work. From the inscription on the label, it was possible to make out that the total power of this power supply is 230W, but no more than 8A can be consumed through the 12V channel. Having opened this power supply, I found that it does not have a microcircuit with the numbers "494" (as described in the article proposed above), and its basis is the UC3843 microcircuit. However, this microcircuit is not included according to the typical scheme and is used only as a pulse generator and a power transistor driver with an overcurrent protection function, and the voltage regulator functions on the output channels of the power supply are assigned to the TL431 microcircuit installed on an additional board:
A trimmer resistor is installed on the same additional board, which allows you to adjust the output voltage in a narrow range.
So, to convert this power supply into a charger, you first need to remove all unnecessary. The redundant is:
1. 220 / 110V switch with its wires. These wires just need to be unsoldered from the board. At the same time, our unit will always operate from 220V, which eliminates the danger of burning it if this switch is accidentally switched to 110V;
2. All output wires, except for one bundle of black wires (in a bundle of 4 wires) is 0V or "common", and one bundle of yellow wires (in a bundle of 2 wires) is "+".
Now we need to make sure that our block always works if it is connected to the network (by default, it only works if the necessary wires are shorted in the output bundle of wires), and also to eliminate the overvoltage protection action, which turns off the block if the output voltage becomes ABOVE some specified limit. This is necessary because we need to get 14.4V at the output (instead of 12), which is perceived by the built-in protection of the unit as an overvoltage and it turns off.
As it turned out, both the on-off signal and the overvoltage protection action signal pass through the same optocoupler, of which there are only three - they connect the output (low-voltage) and input (high-voltage) parts of the power supply. So, in order for the unit to always work and be insensitive to output overvoltages, it is necessary to close the contacts of the desired optocoupler with a solder jumper (i.e., the state of this optocoupler will be "always on"):
Now the power supply will always work when it is connected to the network and no matter what voltage we make at its output.
Next, you should set at the output of the block, where it used to be 12V, an output voltage equal to 14.4V (at idle). Since it is not possible to set 14.4V at the output only by rotating the trimmer resistor installed on the additional power supply board (it only allows you to do something somewhere around 13V), it is necessary to replace the resistor connected in series with the trimmer with a slightly smaller resistor nominal, namely 2.7 kOhm:
Now the output voltage setting range has shifted upwards and it has become possible to set 14.4V at the output.
Then, you need to remove the transistor located next to the TL431 chip. The purpose of this transistor is unknown, but it is turned on in such a way that it has the ability to interfere with the operation of the TL431 microcircuit, that is, to prevent the output voltage from stabilizing at a given level. This transistor was in this place:
Further, in order for the output voltage to be more stable at idle, you need to add a small load to the output of the block through the + 12V channel (which we will have + 14.4V), and through the + 5V channel (which we do not use). A 200 Ohm 2W resistor was used as a load on the +12V (+14.4) channel, and a 68 Ohm 0.5W resistor on the +5V channel (not visible in the photo, because it is for an additional fee):
Only after installing these resistors, you should adjust the output voltage at idle (no load) at 14.4V.
Now it is necessary to limit the output current to a level acceptable for this power supply (i.e., about 8A). This is achieved by increasing the value of the resistor in the primary circuit of the power transformer used as an overload sensor. To limit the output current at the level of 8 ... 10A, this resistor must be replaced with a 0.47Ω 1W resistor:
After such a replacement, the output current will not exceed 8 ... 10A even if we short-circuit the output wires.
Finally, you need to add a part of the circuit that will protect the unit from connecting the battery with reverse polarity (this is the only "homemade" part of the circuit). This will require a regular 12V automotive relay (with four pins) and two 1A diodes (I used 1N4007 diodes). In addition, to indicate the fact that the battery is connected and charging, you will need an LED in the panel mount case (green) and a 1kΩ 0.5W resistor. The schema should be like this:
It works as follows: when the battery is connected to the output with the correct polarity, the relay is triggered by the energy remaining in the battery, and after it is triggered, the battery starts charging from the power supply through the closed contact of this relay, which is indicated by the lit LED. A diode connected in parallel with the relay coil is needed to prevent overvoltages on this coil when it is turned off, arising due to self-induction EMF.
The disadvantages of the received charger include the absence of any indication of the degree of charge of the battery, which makes it unclear - is the battery charged or not? However, in practice it has been established that in a day (24 hours) a conventional car battery with a capacity of 55Ah has time to fully charge.
The advantages include the fact that with this charger the battery can "stand on charge" for an arbitrarily long time and nothing bad will happen - the battery will be charged, but will not "recharge" and will not deteriorate.
Hello, now I will talk about converting the codegen 300w 200xa ATX power supply into a laboratory power supply with voltage regulation from 0 to 24 Volts, and current limiting from 0.1 A to 5 Amperes. I'll post the diagram that I got, maybe someone will improve or add something. The box itself looks like this, although the sticker may be blue or another color.
Moreover, the boards of the 200xa and 300x models are almost the same. Under the board itself there is an inscription CG-13C, maybe CG-13A. Perhaps there are other models similar to this one, but with different inscriptions.
The original diagram looked like this:
It is necessary to remove all unnecessary, the wires of the atx connector, unsolder and wind unnecessary windings on the stabilization group choke. Under the throttle on the board, where +12 volts is written, we leave that winding, the rest we wind. Unsolder the braid from the board (the main power transformer), in no case do not bite it off. Remove the radiator along with the Schottky diodes, and after we remove all unnecessary, it will look like this:
The final scheme after the alteration will look like this:
In general, we solder all the wires, parts.
We make a shunt, from which we will remove the voltage. The meaning of the shunt is that the voltage drop across it tells the PWM how current is loaded - the PSU output. For example, the resistance of the shunt, we got 0.05 (Ohm), if we measure the voltage on the shunt at the time of passage of 10 A, then the voltage on it will be:
U \u003d I * R \u003d 10 * 0.05 \u003d 0.5 (Volt)
I won’t write about the manganin shunt, because I didn’t buy it and I don’t have it, I used two tracks on the board itself, we close the tracks on the board as in the photo to get a shunt. It is clear that it is better to use manganin, but it works more than fine anyway.
In general, they need to be calculated, but if anything, a program for calculating throttles slipped somewhere on the forum.
You can not apply if it is already ringing on the 7th leg of the PWM. It’s just that on some boards on the 7th pin there was no general minus after desoldering the parts (I don’t know why, I could be wrong that it wasn’t :)
We solder the PWM wire to the 16th pin, and we feed this wire to the 1st and 5th pins of the LM358
This resistor will limit the voltage output by the PSU. This resistor and R60 forms a voltage divider that will divide the output voltage and supply it to 1 leg.
The op-amp (PWM) inputs on the 1st and 2nd legs are used to set the output voltage.
The task of the PSU output voltage comes to the 2nd leg, since the second leg can receive a maximum of 5 volts (vref), then the reverse voltage should come to the 1st leg also no more than 5 volts. To do this, we need a voltage divider of 2 resistors, R60 and the one that we will install from the PSU output to 1 leg.
How it works: let's say a variable resistor put 2.5 Volts on the second leg of the PWM, then the PWM will give out such pulses (increase the output voltage from the PSU output) until 2.5 (volts) comes to 1 leg of the op-amp. Suppose if this resistor does not exist, the power supply will reach the maximum voltage, because there is no feedback from the PSU output. The resistor value is 18.5 kOhm.
The load resistor can be supplied from 470 to 600 ohms 2 watts. Capacitors of 500 microfarads for a voltage of 35 volts. I didn’t have capacitors with the required voltage, I put 2 in series, 16 volts 1000 microfarads each. Solder the capacitors between 15-3 and 2-3 PWM legs.
We put the diode assembly that was 16C20C or 12C20C, this diode assembly is designed for 16 amperes (12 amperes, respectively), and 200 volts of reverse peak voltage. The 20C40 diode assembly will not work for us - do not think to install it - it will burn out (checked :)).
If you have any other diode assemblies, make sure that the reverse peak voltage is at least 100 V, and for the current, whichever is greater. Ordinary diodes will not work - they will burn out, these are ultra-fast diodes, just right for a switching power supply.
Since we removed a piece of the circuit that was responsible for supplying power to the PSON PWM, we need to power the PWM from the 18 V power supply on duty. Actually, we install a jumper instead of transistor Q6.
Then we cut the common minus that goes to the body. We make sure that the common minus does not touch the case, otherwise, shorting the plus, with the PSU case, everything will burn out.
This voltage will be used to power the volt-ammeter.
We will use this wire through a 58 ohm resistor to power the fan. Moreover, the fan must be deployed so that it blows on the radiator.
We solder the wires, as well as resistors to them. These wires will go to the LM357 op amp through 47 ohm resistors.
With a positive +5 Volt voltage at this PWM input, there is a limitation of the regulation limit at the outputs C1 and C2, in this case, with an increase at the input DT, there is an increase in the duty cycle on C1 and C2 (you need to look at how the transistors are connected at the output). In a word - stopping the output of the power supply unit. This 4th PWM input (we supply +5 V there) will be used to stop the PSU output in the event of a short circuit (above 4.5 A) at the output.
Attention: this is not a full version - see the forum for details, including photos of the conversion process.
Discuss the article LABORATORY PSU WITH PROTECTION FROM A CONVENTIONAL COMPUTER
