# ATX 12V DC supply

I am using PSTC-12500 power supply unit to power up USB cameras. On the datasheet it says it can provide upto 60A on 5V rail. I highly doubt it, cause our system requires not more than 34A on 5V rail. How can we test peak current on 5V rail?

• Why do you doubt the datasheet? Is your system failing somehow at 34A? You didn't specify. – Adam Lawrence Apr 20 '17 at 20:11
• Also, are you sure you want to test the "peak" current and not the maximum? Those are different values. A "peak" current is a short burst at a specified time period, where as a "maximum" is for continuous use. The testing will be different. – Jim Apr 20 '17 at 20:42

There is a note that says this on the product page:

Note:Combined Total Power From +3.3V And +5V rails Not to Exceed 250W.

So $\frac{250 W}{5 V} = 50 A$ which is contradictory, but I wouldn't be surprised if it could 'peak out' at 60A.

How can we test peak current on 5V rail?

Find a few really high powered resistors and put them in parallel, you'll need a really small resistance. You'll need to be able to dissipate ~250W.

$\frac{250 V}{5 A} = 0.083 Ω$

So if you had 12 1Ω resistors in parallel that would give you 0.083Ω. And the resistors would need to dissipate 25W each. Or you could test it to 40A and you would need less resistors. Or you could add them in one at a time, measure the voltage and see where the supply drops out.

• If you could, mark it as answered – Voltage Spike Apr 21 '17 at 19:11