Switch rated 3A at 125VAC - how many DC amps ?

[RPatrick]

Hello,

I have a pushbutton switch rated for 3A 125VAC and I am considering using it in a DC application at 9.6 volts. Is there any way to tell how many amps it will handle DC from this info?

Thanks !

[steve lewin]

Not really but a quick look at a few catalogues suggests that the DC rating may well be about the same i.e. 3A. I certainly wouldn't use it for more than that as DC is generally harder on switching contacts than AC.

Steve

[Mr.RC-CAM]

Switches that have a 125VAC current rating will have identical low voltage ratings.

Mr. RC-CAM

[BMatthews]

The above are all correct but having said that I've been using a micro toggle switch to control my E power glider for dozens of flights with no problem. It's also a 3 amp switch that's carrying 16 or so amps.

In practical terms the currect capability is controlled by the contact resistance. This resistance warms the switch and in extreme cases will cause the plastic parts to melt and then the switch will deform and fail. For some applicatons the switch may function fine at first but the small sparks that occur during the disconnect will erode the contacts and raise the contact resistance over time so the switch can fail later on.

For the time being set it up with your motor (I'm assuming that's what this is for) and run it for a while with the switch out of the prop blast. If it gets more than slightly warm then it's a good bet that it's living on borrowed time. If it stays cool then it's probably fine.

If you're making a small starter or something like that for very short term duty then go ahead and just do it. If it doesn't get overheated under your finger tip it'll probably live a good long life.

[RPatrick]

Thanks for all the great input. I can always count on Ezone when I need sound technical advice !

On the box the switch said 1.5A at 250VAC, and 3A at 125VAC. I was wondering if continuing to halve the voltage would continue to double the amperage capabitlities. By looking at it (it looks pretty light duty) I have to agree with you guys. Its probably good for about 3 to 5 amps. I am going to do the safe thing and just get a bigger switch.

[boomerace]

Cut your switch into the red wire going from the esc to the RX. Then even a micro switch will do the job! In fact this is what Castle Creations recommends for a brushless esc!
boomer

[RPatrick]

This switch is not going to be used with an ESC. It is for a non - RC project, and will need to carry the full amperage load.

Sorry for the confusion.

Great point though !