Re: Pullup resistor on a NC touch probe, Mach3?

-

> The pull up resistor is necessary. Without it when the switch opens the
> pin is just floating, nothing causes it to go to a high condition. With
> the pullup when the switch is open the resistor pulls the pin to +5

volts.

>
> If the probe switch is closed when the probe is NOT touching anything,
> then this would be an active high signal- it will normally be at

ground-

> low- until the probe touches something, then the pullup causes it to go
> high.
>
> ron giger
>

I should have said the probe is NC when not touching, the circuit
opens on a touch. I have it set up directly to the pins, 11 and gnd,
active high, and it seems to be working. But I didn't think it was
good to have a NC switch connected directly to the parallel port pins.
It looked like a limit switch to me, and seemed to need a pullup
resistor.

thanks,
Monte