Re: Minimum switch current
- From: Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx>
- Date: Wed, 01 Aug 2007 16:59:21 +0100
John Fields wrote:
Eeyore wrote:
Robert Scott wrote:
I noticed that some switches are specified for a minimum current as well as a
maximum current. Someone once told me that this is because that minimum current
is needed to "burn away" oxides where the metals contact. Well, this is a
problem for me because I am designing a low-power device that will run on a coin
cell battery. The switch that I want to use is specified for 1 ma. minimum
current. But I want to use the internal microcontroller pull-up for this user
input switch. Are there some types of switches that have no minimum current?
How much trouble can I expect if I just ignore the spec? What about putting a
01 uF cap around the switch to produce a short burst of high current when the
switch is closed?
A capacitor is probably the worst idea ever.
What you're describing is usually called 'dry switching'.
---
Whether that's what it's usually called or not,
It's the term I'm familiar with. In a typical application you might be switching say
50uA as a control signal. That's dry enought for my liking.
it's wrong. Read my reply to Sloman's post in this thread.
I don't agree with your post.
My answer does at least point out that there are switches designed for this kind of
use. Tact switches would be a classic example. Gold plated contacts are not essential.
http://www.google.com/search?&q=tact+switch
Graham
.
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