AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Steven Hodge" <stevehodge@...> 
wrote:

> ... the actual data sheet ... says
> ... "gold: 0.4 VA max @ 20 VDC or
> peak AC".   Does that seriously mean
> the switch can only handle a pathetic
> 33 mA at 12 VDC (or 20 mA at 20 VDC)?

Once you're reading the data sheet, your beef is now with the 
manufacturer.  Either use another switch, or ask the manufacturer to 
clarify.  My guess is that "VA" is a misprint and the switch can 
handle 0.4 amps.  But, don't act on my guess.

> In my case the switch is input to a
> regulator which ... has the usual
> input capacitor on it.  Does this
> qualify as a resistive load?  It
> would seem to me that it does.

How can a capacitor qualify as a resistive load?  But, it isn't an 
inductive load, which gets rid of the biggest problem.  With a large 
capacitive load, the weird stuff happens when the switch makes and 
the break action is benign.  You'll get a large surge current on the 
make.  My opinion is that for your microcontroller application you 
can ignore this.  All other things being equal, just choose a switch 
with a slightly higher current rating than you need.

I don't think anyone is in disagreement here.  Someone said that if 
the manufacturer chooses not to give a switch a DC rating you should 
not use it in a DC application.  That's a fairly strict position to 
take and I would be a bit more relaxed myself, but it is the 
technically most defensible thing to do.

Graham.