Jim Wilkins wrote:

On Apr 2, 6:58 pm, "Karl Townsend"
wrote:
I need to control a pot with my CNC control. One option is to get a pot
turner like this:http://www.cnc4pc.com/Store/osc/prod...25&products_id...

This would work but I'm not real keen on having a device to physically turn
a knob.

I've got a whacky idea that I'd like to run past the EE types in the group.
I have a large number of unused Opto 22 digital outputshttp://www.opto22.com/site/pr_details.aspx?cid=4&item=G4ODC5

For sake of argument, lets keep the numbers simple. Get four resistors, 100,
200, 400, 800 ohm in series in place of the pot. In parallel with each
resistor put an opto output. Then using base two, any resistance from 0 to
1500 ohms is possible. The switch time on these outs is 100 microseconds -
I'm thinking a pot to control power level on the plasma cutter couldn't
possibly notice the switch time. I don't know if these devices will work at
0 volt between the otpo 22 output connections.

Or is there another easy way to do a pot with a CNC control?

Karl

What you suggest would work if the pot is a two-terminal variable
resistance.


If it's two terminal, then it is a Rheostat, not a Potentiometer.


If it is a three-terminal voltage divider you need to
understand and describe the possible CNC outputs and pot circuit more
thoroughly.

FETs have an ON resistance well below 1 Ohm without an offset at zero
volts.

http://en.wikipedia.org/wiki/Digital...alog_converter

jsw


--
Lead free solder is Belgium's version of 'Hold my beer and watch this!'