Thanks for all your help I have now got the probe working. I added a
pulldown resistor had to fiddle to get the right value 3.3k proved fine.
Alan
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On Wednesday 01 July 2009, alan battersby wrote:
>Hello everyone,
>I thought that I would make a probe for my setup. My idea was to have
>one fixed plate and one movable plate attached to the probe head. These
>plates are initially in contact and move apart as the probe hits the
>surface thus brea
Parallel port pins typically are open collector (They can only sink current
to ground) with an internal pull-up resistor.
You will need to short to ground on contact or add an inverter to your
setup.
alan b
Dave Caroline wrote:
>short to ground the input probably has a pull up resistor
>
>Dave Caroline
>
>and maybe invert the sense
>
>
Even better would be to pull up to +5V with a 4.7k or so resistor, and
have the switch short to ground. This way, you're not relying on the
parallel port pull-up
short to ground the input probably has a pull up resistor
Dave Caroline
and maybe invert the sense
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