I have had some challenges getting spindle speed control working correctly for my mill.
My mill is an X3 with a CNC4PC C11G break out board and Mach 3.
The speed control is wired as per:
The problem I am having is that the spindle doesn’t start unless I have the speed set to 2000rpm or higher. The range for my spindle is 1000 rpm – 3100 rpm and I have the pulleys set to 1000rpm (low) 3100rpm (high.)
I have tested the voltages coming off of the speed control on the C11G and I see 10.95 volts at the 3100 rpm and about 3.2 volts at 1000 rpm.
What seems to happen is that the relay to turn on the spindle doesn’t switch (you can hear it click) until about 6.5v or about 2000rpm. You have to set tie spindle to higher than 2000rpm to get it to start spinning. Once it is spinning, you can then slow it all the way down to 1000rpm.