Thread: Help Calculating Switch Rating

.1 amps at 12 volts if my brain is working... Current rating of the switch won't change, it has a designed maximum current rating, and a maximum voltage rating. You can run it at a lower voltage, but you can't exceed its current rating. Total load is 8 watts, that's a different story. 8 watts at 12 volts is .67 amp, but that will kill the switch.

Also, is the switch designed for AC or DC? A maximum AC current rating will be a lot higher than a maximum DC current rating for a given switch.

It depends on what kind of load the switch is rated for. Inductive loads (eg brush motors) will cause a significant arc, burning the contacts at higher operating voltages. Plain resistive loads will arc less so there will be less difference in current handling capacity from high to low voltages. Basically there's the current the switch will hold long term without melting, and the current at which the contacts rapidly evaporate when used to break a circuit frequently.

I'd find out more about the switch before proceeding with its re-use in a 12V system.

Originally Posted by bee utey

I'd find out more about the switch before proceeding with its re-use in a 12V system.

Agreed, and if it is only rated at .1 amp, it can't be much of a switch...

It is the DB3 model microswitch - 0.1A @ 240VAC (so correct, not much of a switch )
*link to datasheet in post below

But also has a VDC rating which is 0.1A @ 80VDC

I need to switch a solenoid that pulls peak 0.8amps at 12v. Trying to figure out if the switch is good for that or if I need a relay.

So we think a drop to 12v makes no difference to amount of amps it can handle?

I wouldn't use that one for what you want, it won't last 5 minutes. Does it need to be a micro switch like that - what application is it being used in? There are plenty of micro switches that will drive that coil without issue, but not that one...

whoops this is the correct datasheet
http://datasheet.elcodis.com/pdf/19/...0/db2ca1aa.pdf

Originally Posted by bacicat

I wouldn't use that one for what you want, it won't last 5 minutes. Does it need to be a micro switch like that - what application is it being used in? There are plenty of micro switches that will drive that coil without issue, but not that one...

See this post:
http://www.aulro.com/afvb/projects-t...ml#post1871275

I figured I could use it to trigger a relay but then wondered if it could handle it without one... I suppose not.

So its not good for any more than 0.1Amps at 12V then?

Power = current^2*resistance

Voltage is irrelevant.

If you draw 0.8A through the switch, it will have to dissipate 64 times more energy than it's rated for. I'd be very, very surprised if it survived.

-Martin