Monitoring ATX Power Supply w/ Arduino

Projects General Guidance
1

I'm trying to make a quick ATX (computer) power supply monitor, specifically to determine how much power is being used on each line. I'm mostly concerned about +3.3V & 5V, which should help keep voltages in a safer level to avoid blowing up stuff. I'm not familiar with Arduinos, but I was thinking this might be a good project to learn about Arduinos. I'm not sure if the best way to do this would be some current shunts or hall effect sensors, it looks like both would work, but current shunts will leave me with a mV-level input to the Analog Input pins, and I'm not sure if that's going to leave enough resolution to make an accurate reading. I've found some hall effect sensors that look like they'll work, but they're more expensive than I'm looking for at the moment. From a couple of hours of research, it looks like either method should be pretty easy, but I was wondering if anyone can give me advice on what may or may not have worked?

Also, I was hoping to output to an RS-232 port for simple record keeping, I'm a little confused on how the serial monitor works, or if I'd need to buy/make an RS-232 shield.

Thanks!

2

Just got the PDF of a 1-wire battery monitor today, I think it can be used for a ATX supply too - Mixed-signal and digital signal processing ICs | Analog Devices -

The Arduino has a 1-wire library and I think it would make a nice project.

Rob

3

Hi,

You might consider using an Op-Amp to amplify your input signal, this could be good as they are very high impedance and hence the monitoring equipment wont affect the value it is watching.

As for the monitoring, the Arduino boards usually have a USB port on them which can easily be emulated on your PC to behave as a Serial Port and hence no extra hardware is required for this task. You will found a lot of information on this topic as it is a popular method of communication between Arduino and PC.

4

I like the idea of using an op-amp, but what if I wanted to go super simple? I was reading the AnalogRead specs and see that I can provide my own external reference voltage. Can I just provide something small, say 500mV (or lower?), or will the Arduino's ADC not function well with such a low reference voltage?