Convert an ATX Computer Power Supply Into a Bench Top Power Supply

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I have a few 12 V motors and other sensors/electronics that require anywhere from 3-12 Volts. I usually use a battery pack but did not want to continue to go through batteries. For prototyping, I decided to convert an old ATX power supply into table top power supply. This generally will allow you to have terminals for +12V, +5V, +3.3V and potentially a -5V and -12V. These voltages are pretty common for anyone who works with micro-controllers and sensors.

This project uses:
-Project Box
-x2 mounted LEDs
-ATX Power supply
-Various heat shrink sizes
-Toggle Switch
-x2 5 watt resistors
-x2 330 ohm resistors

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Step 1: Preparing an Old ATX Power Supply

There are a bunch of references for building them. First thing I did was find a supply laying around I could use. You can reference the diagram below for the color coding of the ATX supplies.

ATX supplies can put out a good amount of current. If the maximum amount of current were to be pulled I recommend using all the wires at  a given voltage to withstand max current draw. It may be 12 ground wires and 4 +3.3V wires etc...

**WARNING!!!! BEFORE CUTTING WIRES, USE A MULTIMETER TO CHECK THE CAPACITORS TO ENSURE THEY ARE NOT STORING ANY ENERGY. IT WOULD ALSO BE  A RECOMMENDATION TO LET THE SUPPLY SIT FOR SEVERAL DAYS FOR ANY CHARGE TO DISSIPATE"

Remove the cover and cut the adapters off of the wires coming from the supply. You should be left with a large amount of wires that will need to be stripped. 

Step 2: Preparing You Project Box

I went ahead and purchased the box from Radioshack for a few dollars. You may find other tutorials that modify the power supply box. In my case, the supply had a fan on top which limited the room I had for terminals, switches and LED's. I used INKSCAPE to layout what I wanted my box to look like. I printed it out actual size and used it as a template to drill the project box out. I had one swtich, 2 LED's and 5 termianls for my wires. I drilled a large hole in the back to thread all the wires through. 

Step 3: Wiring the Power Supply Up

The same color lines should be soldered together for wiring the supply to get the max amount of current the supply can provide. Once you get the ground and voltage wires together you are a left with a few others. My supply did not have a -5 V. The BROWN wire is the +3.3V sense with needs to be tied in with the +3.3V line. The GREEN wire is soldered to the switch on my supply. The PURPLE wire attaches to the red LED and the GRAY wire attaches to the green LED. 

All the solder connections should utilize heat shrink in the event a connection comes lose and to ensure you get no shorts in the system.

The schematic would be as follows. I did not utilize the fuses in line. The resistors are required for the LEDs and I bought a round switch. Wiring for all other components is correct. I used 2 5 Watt resistors in series in place of the one 10 Watt. Some supplies require an initial load in order to turn on. Before turning your supply on you should CHECK ALL YOUR CONNECTIONS TO ENSURE THE SYSTEM WAS WIRED CORRECTLY.

The red led will turn on when the ATX supply is plugged in. The green led will signify the switch is turned on, supplying power to the rails. Everything worked great and I was very pleased with how everything turned out.

I have a few references on my blog site that have some additional detail.

http://yetticave.blogspot.com/

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    14 Discussions

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    mspencer8

    3 years ago

    Hey what should i do if i want to add several binding post to have different amperage on 5v rail?

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    andrea biffi

    5 years ago on Introduction

    Nice blog! :-)
    about power supply I always would warn about using a lethal power of 400 watt or more for hobby purpose...

    6 replies
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    billbilltandrea biffi

    Reply 5 years ago on Introduction

    Lethal power??.. WE are talking about maximum of 12 VDC here... Not lethal... The wattage has nothing to do with it being lethal... It is voltage at amps that kills..

    0
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    LaurinCbillbillt

    Reply 3 years ago

    Do Not be FOOLED! 1 Volt at 1 Amp has the potential to KILL YOU! I agree it is usually higher voltages that are Dangerous, but this supply must be respected just as any Potential Shock Hazzard Needs to Be! The more one get shocked the lower voltage it takes to feel it. I have been doing electronics for over 50 years and have been shcoked many times, even have a few scars from one or two incidents. I am to the point now that I can feel a shock of the electricity flowing on occation from touching across a 12 car battery connection.

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    jprofferLaurinC

    Reply 3 years ago

    1v 1A definitely CAN NOT kill you. 1v 1,000 A, maybe. It's current that kills, not voltage. You feel the thump of a 12v battery because it has between 400 and 1,000 amps. There's absolutely no danger in an ATX power supply's 12/5/3.3v output.

    0
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    LaurinCbillbillt

    Reply 3 years ago

    Do Not be FOOLED! 1 Volt at 1 Amp has the potential to KILL YOU! I agree it is usually higher voltages that are Dangerous, but this supply must be respected just as any Potential Shock Hazzard Needs to Be! The more one get shocked the lower voltage it takes to feel it. I have been doing electronics for over 50 years and have been shcoked many times, even have a few scars from one or two incidents. I am to the point now that I can feel a shock of the electricity flowing on occation from touching across a 12 car battery connection.

    0
    None
    LaurinCbillbillt

    Reply 3 years ago

    Do Not be FOOLED! 1 Volt at 1 Amp has the potential to KILL YOU! I agree it is usually higher voltages that are Dangerous, but this supply must be respected just as any Potential Shock Hazzard Needs to Be! The more one get shocked the lower voltage it takes to feel it. I have been doing electronics for over 50 years and have been shcoked many times, even have a few scars from one or two incidents. I am to the point now that I can feel a shock of the electricity flowing on occation from touching across a 12 car battery connection.

    0
    None
    LaurinCbillbillt

    Reply 3 years ago

    Do Not be FOOLED! 1 Volt at 1 Amp has the potential to KILL YOU! I agree it is usually higher voltages that are Dangerous, but this supply must be respected just as any Potential Shock Hazzard Needs to Be! The more one get shocked the lower voltage it takes to feel it. I have been doing electronics for over 50 years and have been shcoked many times, even have a few scars from one or two incidents. I am to the point now that I can feel a shock of the electricity flowing on occation from touching across a 12 car battery connection.

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    JamieB1

    4 years ago on Introduction

    what is the -12 rail used for and do i need it to make the power supply?

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    billbillt

    5 years ago on Introduction

    Great Job!!... I am glad this was presented again... I have made dozens of these over the last ten years... There are still some people on earth that will not believe it is possible for this to work... These make a very powerful and trouble free power supply..

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    davehartles69

    5 years ago

    Do you have entered any pictures of your actual wiring?

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    Grunambulax

    5 years ago

    Good idea well executed.

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    petercd

    5 years ago on Introduction

    I dont know if you are aware of it, but in the first pic, the large comment box has obscured all the smaller inner ones, so all you can see is the "project box radioshack" comment. Perhaps you can edit it to be long and thin highlighting the top of the box so that it doesnt obscure the others.

    Overall, nice one, good pics and covered all the details.

    1 reply