Re: Opinions: Hall Effect (digital output type) as limit switch???

Hi Alan,

Good points!

>>What about optical interrupter type sensors?

I wonder if you could make a sealed unit with a vane that's actuated
by a lever...
I retrofitted a Roland Guitar effects pedal from microswitch( which
squashed to oblivion ) to opto-slot detectors once. It worked for
years, but eventually dust got in there. Was easy to cleanout.

>For the "known problem" of power supply failure, with the proper
>"logic", it might be possible to make them "fail open", that is to
>say,if the power to the sensors fails, it causes a limit signal.

Yeah! if you add a diode with a cathode pointing to the supply, anode
to the output, and a series smt fuse/resister to the sensor
supply,and a resister( 1k) across the power leads at the sensor, when
the supply(or sensor short) failed, the output would be terminated to
ground via the diode on a sensor power fault; either at the sensor or
at the main sensor supply. Hmm....

>P.S. I've seen Hall effect switches on some old 5.25" floppy drives,
>That might be a source of cheap switches to experiment with.

I'll check... Digikey has them for under $2 too.

Thanks,
Lee