The reason I asked about the closed loop was to see if the system really could produce enough volts to bring it up to speed - it obviously can't. There's something basically wrong with either the rate of pulses being produced by Mach, or the conversion to volts. If you have a 'scope you could monitor the incoming step pulses and see if they do correspond with what you're asking for. I would do all this with an open loop.
Regarding the step width, I find that it doesn't make any difference to the speed - but of course I have a different Bob to you.

I am using a 2hp Baldor three phase AC motor and a teco FM100 VFD . My Encoder(pulse generator) is on the spindle. I am currently running it 1 to 1 to avoid any confsion , the pulley ratio in mach is set for 1 to 1 also. Mach is reading the spindle speed from the pulse generator and I am verifying the readings with an optical tach at both the motor output shaft and the spindle. The encoder is giving accurate readings in mach. My problem is the VFD is looking for a signal between 1 and 10 volts to vary the speed from 400 rpms to 2200 rpms as measured at the motor output shaft and I cant get a high enough voltage out of my analog output unless I have some wild speed entered like 10,000 rpms


My only problem currently is getting the speeds called out (s***) to give me a suitable voltage at the analog out put on the cnc4pc breakout board.  Any value under s1000 has an output of less than 1 volt which is not high enough to even get the motor to turn I have to enter values like s20000 or higher to get the full 10 volts from the analog output.
Does anyone have any thoughts on how I might be able to adjust the output voltage to be in the range needed for the speeds I am calling out , I need values more like 2volts when s150  but currently have to enter a value of s3000 to get 2 volts at the analog output terminals on the cnc4pc board. I can do the fine tunning in the vfd if I can just get it in the right range.

I also wonder how to get the pulse width value in motor configuration to remain constant and not drop by 1 each time the motor config window is opened

In your case, Id call an S100000 as previously posted, then measure the result. Lets say you get a real rpm of 3000 , so then select configure pulleys, and set the pulley max to 3000.
 Now select S3000M3, and the spindle will then do 3000RPM, then select S1500 , what RPM do you get? Should be close to 1500 if your vfd is linear. Slowly decrease will the voltage is too low to run it, then set that S speed as the pulley minimum, then check linearity and see what happens.. Is it better?

Art

Don't forget that you do have some adjustment of voltage output on your Bob according to the PDF. I'm a bit surprised though that it isn't much higher already.

Tony

I know you'll have done it, but I'll ask anyway. Have you connected the auxiliary 12v supply to the analogue output stage? I hadn't realised, until I read the pdf in a bit more depth, that the analogue side is powered separately from the rest of the board. If you haven't it will certainly give very low outputs.


Tony

yes I have the 12v power supply attached  to the analog side. 
I set up the spindle pulleys as reccomended and am now getting the values I need, I guess I dont fully understand setting up the pulley ratios. Thanks For all the help

I think I have figured out where my confusion was, I was thinking the max speed value in pulley set up was just a limit on the maximum speed the software would allow but its actualy the speed at which the full 10 volts is avail thru the analog out put. I had the value set at 20k so I had to have s20000 to get a full 10v out, reset it to 3000 and its now in the range I was looking for

Ah I see! I thought the same thing. I've had a little play and achieved a rather better linearity in open loop. My numbers were more or less right, but I hadn't looked at it in that way when setting up.

I'm pleased you're finally getting going. What machine are you using? Mine's the Boxford TCL125.

Tony