I'm in the final stages of my conversion of a Novamill to using LinuxCNC. When I acquired the machine, the original control box was intact and functional - so I'm keeping as much of the original electronics as possible, including the stepper drives and so on. I'm just replacing the old serial port interface card with a Mesa card to handle the motion control. All very straightforward - it really is almost a drop in replacement as far as the steppers, home and ESTOP switches and spindle on/off are concerned. The biggest learning curve has been LinuxCNC - but that was anticipated, and is a different story....

So far I have the steppers whirring, homing working and the spindle relay firing - all good. The final part is to add spindle speed control. I am re-using the original PWM to 0-10v converter card that sits in the side of the control box - it handles all the spindle drive isolation issues, and just needs to be fed with a PWM signal by the Mesa card. Again, straightforward.

My question simply is what PWM frequency I should be using? The Denford PWM to 0-10v converter obviously has some filtering in it, so must expect a certain frequency range of PWM input - but what?

I've searched all the usual sources and forums but found nothing concrete. I wondered if any forum members either had an original Denford and could measure the frequency. Or more likely, anyone who has done a similar conversion and could tell me what frequency they used - successfully!

In the absence of further information I am going to try 100Hz, but am ready to be advised otherwise!

Cheers
Graeme