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Re: Door Bells.
- Subject: Re: Door Bells.
- From: "David Buckley" <db@xxxxxxxxxxx>
- Date: Wed, 09 Jun 2004 06:04:48 -0000
--- In ukha_d@xxxxxxx, "John Andrews" <groups@j...> wrote:
> Don't go for wireless, just take 5 volts from the PC through
> the door bell contact and then to the parralel port - thus
> when someone presses the door bell, the parralel port will
> go high.
Just a bit of general advice as to connecting random contacts to
inport ports - always use a pull up resistor, and the contact to
short to earth when something happens. This reduces (and generally
eliminates) noise pickup, and reduces chances of capacitive coupled
spikes killing something. Just a 1K resistor to 5V is all thats
needed.
Oh yes - you need to turn your software upside down, as "on"
becomes "low".
David.
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