[ChrisAttebery]

Hi guys,

I have a problem I'm trying to solve. I have a C6 speed control hooked to a KBMM motor controller. I'm running the KBMM off of a 220V circuit and using a 90V motor, so I only need about 5V out of the C6 to get top speed on the motor. That end of the rpm range works great. The problem is that the low end needs about .5-.7V just to get the motor turning. I have played with all of the spindle settings in Mach3 but it just wants to put out a nice linear output. At 1000 rpm in Mach I get about 400rpm at the spindle.

I need to find a way to offset the output of the C6. I thought that a non inverting summing op amp would do the trick, but I can't seem to get it working. I'm using a LM741 running off the 12V supply for the C6. The problem is that the lowest voltage I can get on the output pin is 2V. I think I've either screwed up the circuit design or I need a different op amp. I've attached a PDF drawing of the schematic. Can one of you help me out?

Thanks,


Chris