William Bross wrote:
>
> Hi Roman,
> I just pulled out some of my older membrane keypads from 1988 and 1992.
> These have been 'beat to death' in retail industry distribution centers 5
> to 6 days per week, hundreds of presses per shift, 2 to 3 shifts per day.
> On the keys that still work, the resistance is between 10 and 20 ohms.  The
> manufacturers spec is <100 ohms guaranteed.  BTW, these are the all mylar
> keypads, conductive paint traces and metal backplate.  If I have some time
> this afternoon, I'll pull out some of my REALLY abused keepers and do some
> tests on them.  Hope this helps your confidence level.


Thanks very much for taking the time to do that Bill!
That's great news, the design will tolerate some
ohms drift on the contact but there is a finite top
limit to the system. About 300 ohms. I'll put up a
page soon, in case anyone else wants to connect
a 12-key pad to 3 pins on a 12c508 etc, or 16-key
pad to 4 pins. :o)
-Roman

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