These were on sale for $0.79 USD. Now they are now $1.49.
They have 2 key markings for fire, police, and ambulance as
well as 3 green LED, 1 yellow, and 2 red. The size is such
that you can shave off about 3/32" and fit it into clear
covered exterior outlet box. The face is printed on the back
of a clear plastic sheet set into the front so you can peel
it off and make your own if you wish.

http://www.goldmine-elec-products.com/prodinfo.asp?number=3DG1
7927

Allen

-----Original Message-----
From: piclist-bounces@mit.edu
[mailto:piclist-bounces@mit.edu] On Behalf Of Isaac Marino
Bavaresco
Sent: Wednesday, April 03, 2013 8:53 PM
To: Microcontroller discussion list - Public.
Subject: Re: [PIC] Pull Up Resistors

With this arrangement you will need some unusual switches
(three
terminal make-make)

And with the conventional method it is also possible to
detect multiple
simultaneous presses.


Isaac


Em 3/4/2013 19:25, Allen Mulvey escreveu:
> Thank you all for the excellent information and resources.
I
> had checked Microchip and MikroElektronica sites and found
> nothing. I missed the significance of the current rating
for
> the internal pullups.
>
> I have been experimenting with a slightly different kind
of
> matrix keypad. Instead of shorting row and column, it
> grounds both. This eliminates the need to scan and allows
> the selection of multiple key presses although not all may
> be unique. I think much of the problem I have seen has
been
> caused by capacitance. Earlier I didn't think about the
R-C
> timer effect. If I connect the keypad with a foot of cat-5
> cable the 20k resistors work fine. If I use 6" of ribbon
> cable 20k is too big but 4k7 or slightly less works fine.
> There also appears to be a difference depending on which
end
> of the cable the resistors are attached although I have
not
> tested this very well.=20
>
> Thanks again,
> Allen
>
>
>

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