How to make 2 power supplies start at the same time?

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martakz's picture
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Hi

I want to power 2 ATX powersupplies at the same time and make them turn on and off in parrelel. How can I do this? I could splice the sense lines...but I dont think the guy wants this. Would a replay work, using the 12V from a molex to short a sense and the ground?

Cheers

T

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martakz's picture
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Dang...sorry about the typo.

Dang...sorry about the typo. I ment a relay. I could also use a transistor I suppose...

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aladds's picture
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yes, connect the ground and t

yes, connect the ground and the green wires of the secondary powersupply to the switching part of the relay, and the two that control it to the ground and the 5/12v depending on the relay, to the primary powersupply

simple realey

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martakz's picture
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How reliable is a standard 12

How reliable is a standard 12V relay? Its going to be operating a beast of a watercooler and peltier on one of my friends sub-zero devices. I dont want it to not turn on one day!

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G4from128k's picture
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If you are worried that the c

If you are worried that the cooling system won't turn on and that the CPU will fry, then use a fail-safe design. Turn-on the cooling system's PSU first with the main power switch/button and use the relay to activate the PSU for the logic board. That way the CPU will never be uncooled.

martakz's picture
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I'll tell him, but hes pritty

I'll tell him, but hes pritty certain he wants soft power. I'll make it how he requests as I am being payed (peanuts)...so I'll give it ago. Thanks for the suggestions Smile

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martakz's picture
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I'll basically make this [url

I'll basically make this http://www.moddin.net/reviews/dualpsu1/

Out of interest, could I use a transistor instead of a relay? No moving parts and smaller Smile

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martakz's picture
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Ooo! I found some mosfets in

Ooo! I found some mosfets in my tool box! They should work? They are rated at 50V at 20 amps. N channel as well...

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G4from128k's picture
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Another fail-safe is a therma

Another fail-safe is a thermal switch. Many household appliances (space heaters, box fans, etc.) have thermal switches that break 120 AC power if the device gets too hot. If you can find one with the right temperature rating. you could mount one of those on the processor (assuming its properly insulated). A thermal switch would also cover internal failures of the cooling system where the cooler's PSU seems OK, but the pumps or Peltier device are broken.

martakz's picture
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Well, aparently, the bios is

Well, aparently, the bios is set up to force a turn off if the proc reaches over 50C. I just want the second PSU to shut down as well.

I think I will go solid state for this circuit. Relays have a finite life and are a bit slow at starting.

Can I use the n-channel mosfet?

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Eudimorphodon's picture
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Re: Well, aparently, the bios is

martakz wrote:

Can I use the n-channel mosfet?

That's way, way overkill. Just use a simple inverter circuit. The one-transistor+two resistor design featured in Mac->ATX power converter designs should do fine.

(You just need something that'll connect the power-on sense line on the secondary PSU to ground when voltage comes up on the primary. The load on it is going to be miniscule.)

--Peace

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I know its overkill ;) The m

its sure overkill WinkLaughing out loud The mosfets were originally purchased to build some fan controllers (Capable of controlling multiple fans hense the high mosfet rating) and a protoype peltier controller (which will be replaced with PWM. The mosfet idea was just a bit of fun to see how much I could stress my fan controller. With big heatsinks on the mosfets it acutally worked.)

Im only going to use what I have already. I was unable to source those transistors from the iMac conversion easily. Maplin did not have them + they have that massive postage charge. There are no local shops Sad As I have loads of these mosfets lieing around I might as well use them for something useful.

Btw, I was hoping you would reply. I know you have the seen the orgianl iMac PSU. I am pritty sure there is a 12V relay on the board somewhere...near the power plug? Its black, says 12v on it...and looks like one. Could there be one on the board?

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Eudimorphodon's picture
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Re: I know its overkill ;) The m

martakz wrote:

Btw, I was hoping you would reply. I know you have the seen the orgianl iMac PSU. I am pritty sure there is a 12V relay on the board somewhere...near the power plug? Its black, says 12v on it...and looks like one. Could there be one on the board?

I really should throw that out. But since I haven't... ;^>

This is it:

http://www.naisweb.com/j/relayj/mech_jpn/mech_jpn_jw/mech_jpn_jw.html

Or slightly more specifically:

http://www.naisweb.com/j/relayj/mech_jpn/mech_jpn_jw/jw___0001.html

--Peace

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Yup! Thanks, thats the one :

Yup! Thanks, thats the one Smile

I should really chuck mine out too. Its blown and pritty useless, but Im sure I will find uses for more of the components. Im keeping it mainly for that large filter capasitor...

Out of interest...what was that relay used for? The power on and off to the monitor or part of the soft power hardware?

Im definatly going solid state with this mod though...much more reliable than relays and simpler too. Heck, if I get it working its £10 I can spend on some decent components...

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martakz's picture
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Should I add a fewmega ohms o

Should I add a fewmega ohms of resistance between the gate and the earth of the transistor? This is to stop the mosfet allowing too much current to flow throuh to the ground from the 12v activation (First PSU)

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Re: I'll tell him, but hes pritty

martakz wrote:

I'll make it how he requests as I am being payed (peanuts)

Cows don't eat peanuts... do they? Wink ;D

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martakz's picture
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This one does :) Especially

This one does Smile Especially choclolate coated ones. Moooooo!

Btw...its going to be changed back to the MacTV when I find some image edditing software for this Pc.

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martakz's picture
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Well it should looks somethin

Well it should looks something like this?

Ive still got to work out the resistor value. How many amps should I put through the thing?

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martakz's picture
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It needs no resistor. The tr

It needs no resistor. The transistor is has a heigh enough internal resistance according to my multimeter. MY ASS! Its faulty. Once on it will only turn off if the supply voltage is turned off then on then off again.

I need some standard transistors. Anyone got any I could buy? Maplin postal charge is too much..

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