Arduino, Devices and Efficient Power Supply

I released today a solution - simple and very low cost - to have a complete power supply for Arduino applications where the components needs to be powered with medium-high currents at various voltages.

ATX Power 1.1 is the power switcher based on a logic that recreate the same behaviour powering a computer desktop.
Using an ATX Power Supply you obtain a power unit giving to your circuit +3.3, +5, +12 V as needed.
I received on IRC some considerations that it's so simple to short-circuit the power-on signal to the COM on the ATX Power Supply. It's not real: the logic circuit shows when the system is powered-on and when it is in standby mode. Then, as described in all the sites I read and on the ATX12V Design Guide, short-circuiting the power-on signal of an ATX Power Supply directly to the GND should seriously damage the power supplier.

To see the project, circuit, images and more, go to the following link:

This small circuit can work with a variety of ATX Power Supply units, from 150W to 400W.

Did you also think about the minimum load you need on the different lines?

Usually you must know what is the load of every line seeing the specific load of every device. In a specifc case (mine) I'm using 12V to power a DC motor controlled by a darlington with a variable current between 4 and 12 V (corresponding to different rotation speeds) that loads from 1.2 to 1.5 A with a maximum load of 2A per pitch.
The 5V I use to drive three stepper motors that have a load of 1.2A for every channel, controlled by three half bridges. While at least two of three stepper are running via PWM the load is at least 2 - 2.5 A
Then Arduino board is powered by the computer simply because I need a computer connected but there are no problems to power also Arduino. 3.3 V in this application should be used for the thermal sensor to increase the sensibility.

Looks like I may dig thru my parts boxes and see what parts I can come up with for making one of these. I have been just "hotwiring" one to work with a jumper pin up to this point. I have the 555 and the resistors. I just need to see if I can come up with an on/off switch. I may take one off an old copier at my office.

Hi, tell me if you need some parts. Actually I'm using this to power with 5 and 12V a cnc controller I recently built working with an Arduino board that is powered by the usb. It is also possible to make something more sophisticated using arduino to power on or standby the external power sources so everything is controlled by software.

good luck, and if you done something with this project, please register to and post a comment to the project page.

Wow, nice work! I can see a lot of older ATX >400W power supplies are going to be happy. I'll grab one next time I see it. Really a waste to toss them away because new computers are more power-hungry. I don't have a desktop now since I moved too many times.