Pete Keillor wrote:

On Fri, 2 Apr 2010 17:58:04 -0500, "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...roducts_id=179

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 outputs
http://www.opto22.com/site/pr_detail...=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


A lot of the stuff I've used (dc motor controls, vfd's) that has a pot
also has another way to control output, such as analog signal input
terminals. I suppose you've exhausted the possibility of such for
your plasma torch?

Pete Keillor

The plasma cutters don't have such a control input (at least the typical
air plasma units don't), because there is no need for them.

Many units do have a control input for "arc on" and an output for "arc
good" and an arc voltage tap as standard equipment, because those are
the control signals required for CNC control, but arc current is not
needed as a dynamic control.