PSU-On Switch Amperage?

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[H]ard|Gawd
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I am installing a desktop PSU into (or rather outside) of a 1U network appliance however the network appliance does not have a momentary switch to activate the PSU. To work around this I am going to install a SPST switch to toggle the PSU on and off, removing the green wire from the 24-pin connector and another ground wire.

My question is, how many amps should my SPST switch be? I am unsure how many amps the green to GND requires to activate the PSU and thus far have had no luck in finding this answer online. I primarily want to avoid burning the switch up. :confused:
 
Generally, any logic line coming off a switch is going to have a ~10,000 Ohm resistor on it (pulling it either high or low). Shouldn't have more than a couple mA on it.
 
Is this SP/ST switch just going to be a straight toggle switch? Most household circuits on 120/60 are 15 amps. 15A is a pretty common toggle switch.
 
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You could always measure it yourself if you have a DMM. A 1-2A switch should be plenty though.
 
If it was up to me I would simply use the pins on the motherboard for the momentary contact switch and a separate L.E.D for the power switch so that I that I know that the power supply did turn on or blinking like in sleep mode. You would just use a small momentary switch 1/2 amp should be enough and it should work. Also holding down the small momentary switch for four seconds or longer would power down the power supply. Once the power supply is turn on there is a brief brief period of time for the power supply to reach operating voltage to stabilize and then the signal on pin 8 (power good) goes to a logical +5v and tell the motherboard and the CPU to start. This would be easier and idea for me rather than having to mess with the main power connector.
 
jack57 said:
If it was up to me I would simply use the pins on the motherboard for the momentary contact switch and a separate L.E.D for the power switch so that I that I know that the power supply did turn on or blinking like in sleep mode. You would just use a small momentary switch 1/2 amp should be enough and it should work. Also holding down the small momentary switch for four seconds or longer would power down the power supply. Once the power supply is turn on there is a brief brief period of time for the power supply to reach operating voltage to stabilize and then the signal on pin 8 (power good) goes to a logical +5v and tell the motherboard and the CPU to start. This would be easier and idea for me rather than having to mess with the main power connector.
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I think you need to re-read the original post. We're not talking about a computer here.
 
Green wire to ground is only a few mA as said before at a few volts. It's only used for signaling and doesn't carry any significant power.
 
I now understand now that he is using a network attached server that has a power switch but not a momentary switch like on a standard desktop machine. Sounds like you are bypassing the internal power supply in order to use a computer power supply. This may imply that the 24 pin computer power connector is not directly compatable with your device and you are rewiring the computer power supply. Like I said before you only need a small low current momentary switch for your needs.
 
jack57 said:
I now understand now that he is using a network attached server that has a power switch but not a momentary switch like on a standard desktop machine. Sounds like you are bypassing the internal power supply in order to use a computer power supply. This may imply that the 24 pin computer power connector is not directly compatable with your device and you are rewiring the computer power supply. Like I said before you only need a small low current momentary switch for your needs.
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A momentary switch would be completely useless in this situation. Continuity must be maintained between the PS_ON wire and one of the grounds in order to keep the PSU running. A momentary switch cannot do that.
 
Wow, thanks for the posts! As I originally mentioned, this will be for a network appliance (firewall) which only has a single rocker switch on the back of the PSU and now that I have had some time to think things over I am wondering if the mobo has its own circuit for connecting the green and gnd wires together. My appliance currently has a 200watt 1U power supply, which if I remember correctly has the green wire on the ATX connector going directly to the board so I am thinking the board has a circuit that is "always on". As mentioned earlier there is no momentary switch for signaling.



There are 2 reasons as to why I am changing the PSU. 1) It has an annoying 40mm fan for cooling that really ramps up and 2) its old and the 12V line is more like 11V (as measured with a DMM) so it is out of spec. So to work around those shortcomings I will be removing this PSU and replacing it with an external Seasonic 400-watt fanless PSU. Yes, it is slightly overpowered but the reviews at Johnny Guru nailed it at 90% efficient for the wattage I will be running it at. I will post here if I remember with my results, as to if a switch is necessary. I may run the leads through my DMM (thanks for the idea Zero82) to see what the draw is.

One more thing, since this is a desktop PSU and will be external do you guys think that I should run a separate ground wire from my network appliance chassis to the chassis of the PSU? I was thinking this may be appropriate since I was unsure if the PSU typically grounds through the mounting screws when mounted inside of an ATX case.
 
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