System board to control power supply

[MolsonCa]

Not sure where to post this, as it does not completely apply to power supplies or motherboards...

Does anyone know of some simple controller board, just to manage the system power?

I put a box together, just to hold hard drives. It is a Chenbro case with 16 hard drives and a Corsair TX750W (CMPSU-750TX) power supply. It will be used for external direct attached storage for 3 or 4 other computers, via multi lane sas cables.

I would like the power supply to act like an AT power supply with just on / off. Then if there is a power problem, I can be sure that the box will power up, and the drives will spin up.

For right now I have an old atx board in the box, attached to only the power supply. I set the bios to power on after power failure.

This is working ok for now, but I was wondering if anyone has ever used or seen some kind of small board that is designed for this... To just manage the power button. Something that is just on or off, but maintains state over power interuptions

 

[Harvey]

Newegg lists a number of AT supplies.

Mounting one in a case designed for an ATX supply may require some cutting and/or drilling, and you'll need to calculate your power requirements. For example, this WD drive requires:

12 volts @ 490 mA + 5 volts @ 500 mA = 8.38 watts.

For 16 drives that means, under maximum load, your supply must provide:

12 volts @ 7.84 amps = 94.08 watts
5 volts @ 6 amps = 30 watts

The total power required at maximum load = 134.08 watts.

That's actual power consumed if all drives are simultaneously at their most active, and it does not account for the conversion efficiency of the supply, which is less than 100%.

That does not mean you can use any such supply rated at 150 watts, which also includes the rating for the 12 volt supply. You will have to be sure the supply you buy provides the maximum current required at both required voltages.

Also, drives get warm in operation so don't forget to provide adequate cooling and ventilation for this box.

Hope that helps.

 

[MolsonCa]

Yeah, thanks...

I already have the power supply. I was wondering if anyone has seen or used some controller board that accepts the ATX in and handles the power button of the case.

No MoBo needed.

 

[Harvey]

Originally posted by: MolsonCa
Yeah, thanks...

I already have the power supply. I was wondering if anyone has seen or used some controller board that accepts the ATX in and handles the power button of the case.

From that standpoint, the difference is, AT supplies use a hard mechanical power switch while ATX supplies use a logic signal that is a momentary closure to ground. The trace from the power connector on an ATX motherboard goes directly to the logic connection for the power supply.

Once the logic is engaged in the "on" state, it stays on until it receives a logic signal from the system to power down.

 

[myocardia]

You don't need a motherboard, and you don't need an adapter, you only need a $.99 momentary contact switch from Radio Shack, along with reading this page.

 

[MolsonCa]

Fantastic. It looks like it could be just what I am looking for.

I'm glad the thread is finally on the right track.

I tried the opposite of this years ago. I jumped the PWR pin on the mobo, but that only caused the power supply to constantly cycle on and off.

This sollution looks like it would do what I want. I will try it on an old power supply this weekend, then let you guys know if i have success or cook the PS.

 

[MolsonCa]

There is an on off switch on the back of the ps. So I am guessing that I can eliminate the external switch altogether, and just use a wire to jump the leads.

 

[myocardia]

Just leave the PSU's external switch turned on. BTW, I forgot to say that you'll want to cut the two wires, and solder them to the wires from your momentary SPDT switch.

 

[MolsonCa]

Well, it is a nice ps, so I'm not sure I want to wreck it.
I picked it because it has 8 molex connectors + 8 sata connectors.

I may want to use it with a mobo later, so I think I will jump it with a wire for now. I will solder the wire, but I will try to push the leads through the plastic connector first. Then I will tape everything else up.

Thanks for your help. It is exactly what I was looking for.