Using Computer PS - Simple Question

[txcowdog]

I understand the method of using three AT style power supplies in series with a floating ground, but, do I need a bleed resistor or a capacitor across the 12v or 5v output? I thought I read that somewhere, but, now that I am ready to put it together, I can't find the reference. Thanks for any input you might have.

[jerber]

You need a 4R7 10 Watt resistor between the ground and the +5V (red). By an AT power supply the 5V needs to draw at least 1 Ampere in order to work properly.
If you mount the resistor inside the supply in the airflow of the fan then you can get away with a 5 Watt resistor.

By 3 supplies you need 3 4R7 resistors for each supply one. You can also use 1 15R 25watt (or 15W see above...) resistor between the ground of the first supply and the +5V of the third (wich should be +15V).

You don't need a capacitor but it is better if your motors draw alot of current.
And if you going to use a very large capitator then you also want to use a bleeder (in combination with a switch) to discharge them.

You can find some PDF's on the gecko site wich contain info on how big the capicitator should be.

[txcowdog]

Jerber,

I kinda had one figured out, but putting three in series was the stumper. Now I see I need to put a resistor in each PS and it looks like I can get away without a capacitor because the steppers are only 1.4A

Thanks for the help.