Hi, I'm using mach 4 and im trying to set up my rapid change atc, I can control spindle speed with the vfd to be around 1500-2000 easily but on mach 4 it seems my  minimum  spindle speed is set to 8000rpm, I can turn it on and use the override to increase rpm but I cant go lower. even with the command M3 S2000 it still wont go below 8000, where can I find the setting to change this? I have ess installed as well.
Any help would be appreciated, this is the last step I need to figure out.

Thanks

Check the settings in the chart under Config>Control and select the Spindle tab.

A setting such as 8000 minimum is common for 24000 RPM spindles because that is the speed below which the motor will have too little torque to be useful and trying to cut at low speed may cause the motor to overheat, especially if it is not water cooled.

the settings should all be fine, here is a picture of the config and the ess config

Your Mach4 Config>Control settings look correct.

I am not familiar with the ESS configuration page, but your setup seems reasonable.

You can confirm that the ESS and the C25XP are responding correctly by measuring the voltage on the analog output of the C25XP at the two pin connector next to the adjustment potentiometer. If you request zero speed the voltage there should be almost zero. A speed of 2000 should produce approximately 0.8 volts. If you do not get results similar to this, you should consult with CNC4PC and/or Warp9TD.