AC on DC side of PSU?
Hello. The other day I was testing some led's that I intended to use on a new (hopefully) fashionable lid for my computer case. I tested one of them using a resistor and a power supply. But I hadn't even attached the led when I noticed something odd.
When my powersupply is switched off (but plugged into the wall socket), there's an AC current running between me and the ground wire of the power supply - and between me and the 12v wire I meant to use as well in fact.
I tried this with two different power supplies I had laying about (an antec 380w and a modular 620w corsair). The current varies appearently, but it's somewhere between 54 and 110 volts, and as voltage goes down so do herz count. I've seen anything from 25 to 7 hz. Between the two wires, there's less than 0.1v but still enough to detect a 50hz frequency.
When I switch the unit on the voltage becomes half of whatever it was before, and the herz rating changes to 26-27.
There's even enough current to have the diode light up enough that I can tell the colors apart (3 diodes in one housing sharing a common ground) when I use myself as 'plus' and the ground from the psu as ground.
Why? Why do I detect ac current on my power supply?
When the unit is turned on I'm measuring very close to zero voltage ac between ground and +12v, but I still have a 50hz reading on the multimeter. Switching from raw dc reading (of 12.08v on the antec) to ac+dc I notice the voltage reading changing, but the herz is still @ 50.
I'm just a simple enthusiast. I would've always claimed there's no ac on the dc side of a power supply - but appearently that's not so.
Why?
background:
System's in denmark. Means 230v @ 50hz from the wall socket.
multimeter is an mx53 (http://www.aemc.com/products/html/mi...bname=products)
Power supply is turned on by shorting green and a ground on the atx plug using wire from another atx plug that I had cut to pieces a while ago.
I already asked toms hardware some days ago, but the only answer I got was to ask an electrician (which I had done, but to no avail) or try posting here.
When my powersupply is switched off (but plugged into the wall socket), there's an AC current running between me and the ground wire of the power supply - and between me and the 12v wire I meant to use as well in fact.
I tried this with two different power supplies I had laying about (an antec 380w and a modular 620w corsair). The current varies appearently, but it's somewhere between 54 and 110 volts, and as voltage goes down so do herz count. I've seen anything from 25 to 7 hz. Between the two wires, there's less than 0.1v but still enough to detect a 50hz frequency.
When I switch the unit on the voltage becomes half of whatever it was before, and the herz rating changes to 26-27.
There's even enough current to have the diode light up enough that I can tell the colors apart (3 diodes in one housing sharing a common ground) when I use myself as 'plus' and the ground from the psu as ground.
Why? Why do I detect ac current on my power supply?
When the unit is turned on I'm measuring very close to zero voltage ac between ground and +12v, but I still have a 50hz reading on the multimeter. Switching from raw dc reading (of 12.08v on the antec) to ac+dc I notice the voltage reading changing, but the herz is still @ 50.
I'm just a simple enthusiast. I would've always claimed there's no ac on the dc side of a power supply - but appearently that's not so.
Why?
background:
System's in denmark. Means 230v @ 50hz from the wall socket.
multimeter is an mx53 (http://www.aemc.com/products/html/mi...bname=products)
Power supply is turned on by shorting green and a ground on the atx plug using wire from another atx plug that I had cut to pieces a while ago.
I already asked toms hardware some days ago, but the only answer I got was to ask an electrician (which I had done, but to no avail) or try posting here.
).
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