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I'm searching for a way to detect over-/undervoltages across the PSU connectors so that i can have a better chance of finding causes for HW failures/errors . Best way i could think of was logging the voltages and see if i can correlate any abnormalities with on-screen errors or system hangs and such. But i can't find any device that helps me log the voltages (If you know of a better way, do tell)

Regards,
Sonny

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1 Answer

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In an ATX PC Power Supply you have 1.2+, 3.3+, 5+, 5-, 12+, and 12- (and possibly 3.3-) voltages. A potential need of monitoring 7 different voltages! While I do not disagree that faulty PS could shorten the life of items attached, it seems like more work than it would be worth. I'd prefer to spend the money for a known accurate and reputable PS...probably the least expensive option.

If you wish to pursue this, you could buy a bunch of cheap multi-meters from a discount tool store. Of course to be practicable you might consider getting an Arduino and program it to monitor the voltages. This forum post shows how to monitor 12, 5 and 3 volts. It should not be difficult to expand the program to monitor additional voltages. With an Arduino UNO you are limited to 6 analogue inputs, so you would need the Arduino Mega 2560 if you need to monitor more.

Furthermore, you probably want to log not just monitor so you'll want to replace the LCD shield (a board which fits on top of an Arduino) with a data logger shield, such as this one.

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I'll have to disagree with this answer. In cases where a power supply is suspect, a multimeter is almost completely useless because of low sampling time. Most cheap multimeters will show only few updates peer second and if voltage regulation of a switching power supply is to be questioned, the noise on the supply is going to be much more important than the average voltage (unless the power supply is really terrible one form the sub $10 range) and the noise won't be picked up by a multimeter. – AndrejaKo Apr 15 '12 at 12:29
To actually monitor the voltages, an oscilloscope is the right tool, but maybe an Arduino sampling at 10 KSa/s could provide some meaningful results. Viewing averaged results on an LCD definitely won't be useful. Perhaps it could be possible to send samples over serial port to a PC and then use some Excel-like program to analyze the results and see the noise itself and check if spikes go out of regulation. – AndrejaKo Apr 15 '12 at 12:33
Also important is to actually know how the power supply generates voltages in order to know which voltages to check. For most uses, the -12 V, which is the only negative voltage currently in ATX specification, isn't important. On the other hand, it's much more important to figure out how exactly the +3.3 V, +5 V and + 12 V voltages are generated, if they are actually coming from different rails or if they only have separate current limiting on each rail. – AndrejaKo Apr 15 '12 at 12:36
Also as far as voltages are concerned, +12 V is the most important voltage since the most power hungry components (like CPU/GPU) today use their own regulators to lower the voltage form +12 V to whatever they need. – AndrejaKo Apr 15 '12 at 12:37
great comment i'm still interested in other opinions the community has to give – Sonny Apr 15 '12 at 16:18

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