Hello everyone,

So i have a problem with controlling my VFD with mach3 BOB

This is the BOB in question: https://www.vallder-rs.com/en/c/300/...s-board-detail

This is the VFD in question: https://www.vallder-rs.com/en/c/436/...nverter-detail ( its 1.5kw one)

Min spindle speed is 6000 and max 24000 rpm.

I connected everything correctly and configured everything correctly i am sure of it.

When i start the spindle at min speed it starts speeding up and stops at 6000 for a second and again starts speeding up to around 12000 and stops there.

When i change speed in mach3 to 12000 ( through S12000 command) it starts slowing down for some reason.

I think i found the problem but do not know how to solve it.

To connect the mach3 BOB to VFD i use 3 VFD screw terminals called FV , GND COM and S1 respectively. S1 is used for starting the spindle and FV is used for +10V analog.

The voltage between S1 and COM GND is 12.3V without anything connected. Voltage between FV and COM GND is 0V as it should be.

I have 4 wires running from BOB to VFD : +10V , GND , relay COM , relay NO.

the problem is that GND and relay COM have to go the same point of VFD ( GND COM);

On BOB without connecting it to VFD 0-10V analog outputs correct voltage for all given S commands.

When i start the spindle on 6000 relay activates and spindle starts speeding up the voltage somehow gets transfered over to FV from S1 and gets higher then it should be, to around 4V between FV and GND COM.

The way to solve this is obviously to isolate GND from relay COM, but i do not know the way to do it.

If this post is confusing i will record a video to demonstrate what is the problem.

Thanks in advance for your responses.