Standard AC light switches and DC power

[strnjss]

I've always been curious about this. I do DC electronic projects sometimes, and will just use a standard AC wall switch to control the power from the battery.

It works just fine. Like say I put a switch in series with a battery and a light bulb, the switch will turn it on and off just fine.

However, on the switches, they all say "AC use only". Why? It works, is it dangerous? Does it provide too much resistance and kill batteries quickly? Or is it just that it's only been approved for AC usage for legal purposes?

Just curious.

 

[nehog]

For voltages less than 32 volts you should be OK. Higher DC voltages do require derating of the contacts, and/or arc suppression circuitry to prevent damage and arc overs.

 

[strnjss]

Thanks that's good to know!

 

[sberry]

No cycle to DC, arcing can be a problem.

 

[ddawg16]

And the other issue is contact material....AC and DC contacts typically use different materials....there is a tendancy for DC circuits to cause an electro-plating action over time.

The type of material also depends on low current vs high current vs low voltage vs high voltage......actually, DC circuit contacts present a bigger problem than AC.

It's all FM....

 

[hillbilly1]

DC has a hotter arc when opening and closing the circuit, ac switches are not durable enough to withstand it, so they will have a shorter life.

 

[strnjss]

ok thanks everyone. This is all exactly what I wanted to know!