Pocket ATX Power Supply


Introduction: Pocket ATX Power Supply

About: Bit of a background in various electrical and mechanical fields, obscure sense of humour and typically willing to help...

I used an ATX extender cable to create a handy device for turning on a computer power supply when it is not in a computer.

This can be used to test a power supply or allow you to use the power for other electronic circuits.

You need to strip off some of the wire insulation from 4 different wires as shown.

Solder the green wire to a black wire then cover the solder joint with electrical tape.

Solder a power resistor between a red wire and black wire then cover the solder joints with electrical tape.

With the supply plugged in and switch in the on position the power supply will not turn on. When this plug is connected to the main ATX connector the poser supply turns on.



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13 Discussions

What happens if I touch one of the outputs? let's say the 12v, will I get electrified with the high amp ? isn't that a risk?

2 replies

Usually, nothing will happen. If your skin is wet or you are tired though, you might get the tingles. It´s the same as touching the washing machine when the wall plug is not earthed. Humans can feel really small amounts of electric current if it can pass through the skin.

At the risk of getting into a lengthy debate with both informed and uninformed persons... the short answer to both of your questions is YES!

There is ALWAYS a risk when dealing with electrics whether it is AC or DC. Yours depends on many factors including but not limited to the electrical pathway to ground and the conductivity of your skin. Further, if you are grounded and touch the DC output with metal next to your skin like with a ring, prepare for an instant and nasty burn on your ring finger as the metal heats up rapidly.

We have grown accustomed to, yet incorrectly think that low voltage DC is safe. For example how many times have you put a 9 volt battery in your pocket with loose change or keys, or tested to see if it was live by sticking it on your tongue? Or leaned on a car battery while checking the oil. DC is typically contained in friendly and innocuous looking packages, how can it possibly hurt us?

Just remember that ANY Voltage and Amperage combination can be lethal under the right circumstances.

Treat any electrical source with respect!

I just connect the green wire to a black wire / case using another wire / conductor...

This is quite clever; I'll have to salvage a couple junked supplies and do this. Have you thought about creating one with just dedicated banana plug connectors or the like to pop on a random PSU?

1 reply

What is the point of the resistor? I'm very curious... I've never used one with my ATX PSU conversions...

1 reply

The PSU is a switched-mode type of power supply. Most power supplies of this type need at least a small load function properly. That is why we need a load (The resistor).

Very smart trick. well done.
I have heard that a 30 ohm resistor will also work and draws less power.

1 reply

I've seen the 30-Ohm hard-soldered into the board between the +5V & GND on a lot of supplies over 300-Watt.. I can imagine that 10-Watt 10-Ohm is still drawing down some of the voltage, despite the supply bumping up the output to match.. It's mainly a minor load to maintain the switching circuitry. (if there was zero load, the supply would shut-down automatically, sensing an open circuit..) There are some supplies, (some of the 200-Watt DELL supplies, some (Pre-HP) Compaq supplies, the pins on the ATX connector were swapped... (tale of a sudden POP, followed by a wisp of smoke as the LM358N blew-up.) the two converted supplies I have, have a 33-ohm, 5W across the +5V (one, an ANTEC, the 5W metal film resister is soldered to the board inside. the Dell Optiplex supply I converted, I clamped it to the inside of the case in front of the air vent, and flipped the fan to draw air through the case. (old style, it forced it through.. as it was drawing from the CPU.)