RE: how to turn on a power supply without a motherboard

Anonymous Says:
November 29th, 2005 at 9:19 pm e
I have a few questions. First, what are the outputs of your power supplies? I remember MIT saying you need 5V/4A per board. Second, how did you calculate the required resistor values (1.5K, and 3.3K)? And lastly, do you have one power supply per board, or how do you have it setup?

Ok, the resistor to keep the power supply on and the 5 volts with 4 amps are independent of one another.

The PS-ON is a pin on the power supply that is dedicated toward just saying, "Hey, I'm on" and powers up the power supply (PSU). The motherboard normally will create this however here by connecting a ground to it, it creates the connection. Badabing, it turns on.

My resistor values are what was required to keep the power supply on. You could do a straight up wire to do this, but I used the minimal resistor value needed. I systematically went through and found the minimal value for both the PSU's I bought.

The reason why I like computer PSU's are they already have a powerful 5 volt line in them and they are cheap. A multitasker if you will (That's right, I watch Good Eats). Also they already provide a "cleaner" power chances are cheaper than I could custom make an AC to DC power adapter.

From there you only need to worry about Amps. Volts are constant; the amps will split among the "branches".

I have 2 PSU's for my disco dance floor, each power supply is rated to 30 amps for the 5 volt line. Without overloading it, it can then can power 7 boards. It does have a 60 amp overload. I'm opting for caution and using 2 when I could use just one.

To split the power, I created a power splitting block. I have two (one per PSU)

With that, I must go to Diversy Rock & Bowl for ... bowling before my friend Elysia kicks my ass for not showing up to her birthday party. Seriously, she hits ... and hard. And I'm man enough to say it hurts cause I'll send her after you for making me late (which I already am but shhh).