Can I use a switch that reads "15A 120V AC ONLY" on a DC circuit?

Thread Starter

s355

Joined Apr 13, 2021
32
The switch will be connected to the PS_ON and GND of an ATX PSU to power an AT PC. The switch has a sticker that reads "LIGHTED".
 

Reloadron

Joined Jan 15, 2015
5,934
In this case yes, it won't matter. The PS_ON is held at a logic high through a pull up. Placing it at a Logic Low enables the power supply. Since the switch passes no current to speak of yes, what you have will work. Normally you would not use an AC rated switch for switching DC, however, in this case it doesn't matter. The actual current is a few mA. Not sure what the "lighted" is about unless it is an illuminated switch?

Ron
 

Thread Starter

s355

Joined Apr 13, 2021
32
In this case yes, it won't matter. The PS_ON is held at a logic high through a pull up. Placing it at a Logic Low enables the power supply. Since the switch passes no current to speak of yes, what you have will work. Normally you would not use an AC rated switch for switching DC, however, in this case it doesn't matter. The actual current is a few mA. Not sure what the "lighted" is about unless it is an illuminated switch?

Ron
The switch is illuminated.
 

Irving

Joined Jan 30, 2016
1,497
How is it illuminated? Are there separate 'lamp' terminals? Should still work if at least one lamp terminal is separate from the contact terminals.
 

Tonyr1084

Joined Sep 24, 2015
5,969
There's a possibility that the "Illumination" part of the switch MIGHT act as enough of a switch. However, to know for sure, we need to know more about the switch. Does it have a model number? Can you post a picture of it?
 

Thread Starter

s355

Joined Apr 13, 2021
32
How is it illuminated? Are there separate 'lamp' terminals? Should still work if at least one lamp terminal is separate from the contact terminals.
it is in the switch. It is a Cooper toggle switch. No S/N
 

shortbus

Joined Sep 30, 2009
8,570
Normally you would not use an AC rated switch for switching DC, however, in this case it doesn't matter.
I see something similar said here all of the time. But before becoming a member here I have used AC only toggle switches on DC for over 50 or 60 years. With out ever having one fail.

Guess I've either been extremely lucky or this is just another of those theoretical things that don't mean much in real life? As a lifelong machinist there are many things I've read in books that you can't do, that work just fine when you actually do try them, and I think this is another thing like those.
 

Lo_volt

Joined Apr 3, 2014
189
Normally you would not use an AC rated switch for switching DC
@shortbus Arcing is an issue with high voltage DC. DC rated switches require specialized designs to reduce the possibility of arcing when the contacts are opened. This typically involves vanes to cut an arc should it occur on opening the switch. Below 50 volts or so shouldn't be an issue.
 

Irving

Joined Jan 30, 2016
1,497
Is it like this? Illuminated toggle 'glows' when off through a 'grounding' connection, so clearly a neon-lamp IMHO.

1622818129417.png
 
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shortbus

Joined Sep 30, 2009
8,570
@shortbus Arcing is an issue with high voltage DC. DC rated switches require specialized designs to reduce the possibility of arcing when the contacts are opened. This typically involves vanes to cut an arc should it occur on opening the switch. Below 50 volts or so shouldn't be an issue.
That is what most people coming here are asking about, usually in a circuit of around 12VDC, and they're told get one for DC and stay away from an AC switch. I used to argue about it but got too much grief from the "experts". Now that I've been granted the "Expert" status I thought maybe it was time to bring it up again.:)
 

Reloadron

Joined Jan 15, 2015
5,934
@shortbus Arcing is an issue with high voltage DC. DC rated switches require specialized designs to reduce the possibility of arcing when the contacts are opened. This typically involves vanes to cut an arc should it occur on opening the switch. Below 50 volts or so shouldn't be an issue.
OK, I confess I clearly wrote it backwards. I always liked this little video. I think we all can agree that in this situation any switch will work. In the case of some illuminated switches the switch just won't illuminate. There is no current to speak of being switched. My apologies for getting things backwards I will consider turning myself in for firing squad in the morning. :)

Ron
 
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