It may be more cost effective to use a mosfet and a resistor and a low
current switch. You can buy lots more mosfet for  your $ than you can
switch. A small switch that shorts gate to source a 1M resistor form batter=
y
to gate. Switch rating is then mA and really cheep.

Steve

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Christopher Head
Sent: 19 August 2011 07:48
To: piclist@mit.edu
Subject: [EE] Switch Contact Ratings

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Hi everyone,
I'm looking for a power switch. The power supply is a four-cell LiPo
battery giving up to maybe 17V at full charge. The circuit behind the
power switch may occasionally draw up to 10 to 15 amps. Here's the
kicker: the circuit will never be drawing anywhere near that much
current *when the switch makes or breaks* (expected current draw
during a make or break will be less than 1A, much less for breaking,
slightly more on making than breaking due to capacitor inrush). I'd like
to avoid switches that are rated in the usual way for 15 amps or so, as
those are rather large and expensive for the the project.

It seems to me that switches should experience one of two causes of
failure, either excessive arcing on make/break or excessive resistive
heating while closed. It also seems to me that arcing should be rather
more damaging to the average switch than resistive heating, which leads
me to suspect that an average switch should have a much higher
closed-continuous current rating than its make-or-break current rating.

Unfortunately, the switches I've looked at have only a single current
rating (or a couple at different voltages), and I can't seem to find
any information about this. It's probably a rather uncommon use of a
switch. Does anyone know about this kind of application?

Thanks!
Chris
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