AVR-Chat

On Wed, Mar 19, 2008 at 08:22:11AM -0700, Steven Hodge wrote:
> 
> However, I am switching over to a uC system and now want these
> switches to just supply a logic signal, 3V level.  After the responses
> to my original post I checked the specs on the switches.  The NKK have
> parts which are various combinations of copper and silver, but no
> gold.  The Honeywell data sheet says "Honeywell MICRO SWITCH does not
> recommend the use of silver cadmium oxide switch contacts in
> non-arcing loads. Non-arcing loads are generally loads less than 12
> volts and/or 0.5 amp. NT switches use silver cadmium oxide contacts."
> This is interesting because even my original use of them (12V, 20 to
> 300 mA) does not meet this spec but nonetheless the switches have
> worked fine for 5 years, and continue to do so.  Neither data sheet
> specifically specifies a minimum, or wetting, current.

If the switch is regularly toggled the contacts are probably "wiping"
and keeping themselves clean and healthy.

I suggest in your redesign its time to consider membrane switches. There
are shops that can produce membrane panels in low volumes for reasonable
prices. And can build for high reliability and high usage at the same
time. 

Also consider small non-seal switches behind a vinyl membrane. The vinyl
can be formed with a bellows that helps feel the switch boundaries and
add flex for reliability and longer throw of your selected switch.

-- 
David Kelly N4HHE, dkelly@HiWAAY.net
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Whom computers would destroy, they must first drive mad.