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# Can I use AC switches on a DC circuit?

Go to solution Solved by mariushm,

Those switches should be good for up to around 50v DC and up to around 2-3A

Most switches are rated for less voltage and current on DC (or as you can see in the page, they don't mention at all because they're smaller values).

The reason for these lower DC ratings are because each time you change the switch position and the two metal bits get close together to make contact, there's potential to have an electric arc generated between the metals for a few microseconds or nanoseconds until the two metal parts are completely touching. Same deal for breaking contact, as the metal bits break apart there can be electric arcs, sparks etc

These sparks can cause the metal bits to pit or to oxidize, to get a layer of carbon or whatever over the metal, making a poorer contact, which increases the resistance, which in turn causes the contacts to heat more at higher currents.

With AC voltage and currents, you have a sine wave or sort of sine wave (depending on your supply) which goes from some negative voltage through 0v and then to a positive voltage, and then back again through 0v down to the negative voltage (for example your 120v AC  is -170v ... 0v ... 170v , 60 times a second you go through 0v.  So, if there's an arc or something in the switch, every time the AC sine wave gets near 0v, the electric arc is being killed, so the damage is limited to a few ms at most.

I'm planning on using these switches in a circuit I'm building. I'm only planning on putting around 5V through them (4 AAs) so I'm wondering if they'll be fine to use since they only say AC 125V and nothing about DC. Thanks!

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3 minutes ago, Johnprogames360 said:

Maybe you should read the community standards:

On 8/27/2018 at 5:44 PM, Whiskers said:

No spam

And have you even read the OP?

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should be fine, im no expert but i cant see why not. unless those are radically difrent than any switch that looks just like that i have used before they should work just fine for DC too

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Those switches should be good for up to around 50v DC and up to around 2-3A

Most switches are rated for less voltage and current on DC (or as you can see in the page, they don't mention at all because they're smaller values).

The reason for these lower DC ratings are because each time you change the switch position and the two metal bits get close together to make contact, there's potential to have an electric arc generated between the metals for a few microseconds or nanoseconds until the two metal parts are completely touching. Same deal for breaking contact, as the metal bits break apart there can be electric arcs, sparks etc

These sparks can cause the metal bits to pit or to oxidize, to get a layer of carbon or whatever over the metal, making a poorer contact, which increases the resistance, which in turn causes the contacts to heat more at higher currents.

With AC voltage and currents, you have a sine wave or sort of sine wave (depending on your supply) which goes from some negative voltage through 0v and then to a positive voltage, and then back again through 0v down to the negative voltage (for example your 120v AC  is -170v ... 0v ... 170v , 60 times a second you go through 0v.  So, if there's an arc or something in the switch, every time the AC sine wave gets near 0v, the electric arc is being killed, so the damage is limited to a few ms at most.