Proximity Sensors / Mach3 not showing

[irving2008]

Looking at that, the inputs require 7mA at 5V, which somewhat complicates things if using a NPN sensor, as the inputs obvisouly have resistors installed to drive the Optos.

I've got to head to work now, but if nobody has replied by later, I'll figure out some values to use the sensors you have.

assuming 1.2v forward voltage on the opto means that the existing series resistor is (5 - 1.2)/.007 =542, so probably 560R. the suggested series resistors of 1,5k for 12v and 3k for 24v give currents of 6.9mA and 6.4mA respectively.

dropping the 'on' current to 5mA will need a pull up resistor of 220R and the 'off' current through the 220R would be (5-.4)/220=21mA and 0.1W dissipation, needing a 0.25W resistor. I guess 5mA through the opto will be ok and not have noise immunity issues.

It would be better to use a higher supply rail, e.g. 12 or 24v and use the suggested 1k5 or 3k resistors 'off' current/power being 7.7mA/0.1W or 7.9mA/0.2W respectively.