This isn't directly a CNC question, but it's related. I'm trying to make a microcontroller-based speed control for a Brent IE pottery wheel (for our meteorology department; they use it for a spin tank).

The wheel is powered by a KBLC-240D variable speed DC motor control, which is pretty much the same thing (I think) as the KBIC speed control in several Sherline mills (manual here).

The documentation says that I should provide 0-7V between P2+ and F- to enable voltage following, which [url=http://cnc4pc.com/Tech_Docs/KBIC.pdf]seems to agree with. However, I tried this (disconnected the control pot from P2/P3 and connected a bench power supply) and had no luck at all; the motor didn't even turn.

Any idea what I'm missing? I do want to point out that the motor control is wired differently from what I expected; instead of the pot being between P1/P2/P3, the low end (P1) is disconnected entirely making the pot act like a variable resistor instead of a voltage divider, which sounded strange. Additionally, P1 is jumpered somewhere with a resistor, which didn't match what I expected.

Any idea what I'm missing? Thanks--new to me, but once I can figure this out it should be a neat project.