How to attach spindle electrically for cnc shield (grbl) ?
There is a speed control knob attached on PSU.
Spindle to PSU to CNC shield ?
or
Spindle and PSU independly ?
Can´t find a tutorial…
please help, thank You,
Jesse
(Edit to add context - my comments are based on different equipment. Check @dart1280 comment below - he’s using the same spindle and power supply in the question)
The PWM signal from the control board will take the place of the knob currently on the power supply, which is probably providing a 0-5v signal to control spindle rpm.
I have a DPDT switch on my MPCNC installation to allow me to easily change between using a similar knob and allowing CNC control of spindle RPM. I’m using and older CNC Shield/Arduino stack and the PWM AC controller connected to the DW660 spiral cutter, so I can’t speak to the specific RAMBO pin to connect to.
If you have DC spindle, you may also want to use the Spindle Direction pin in conjunction with a relay to allow you to reverse spindle direction. I haven’t tried that myself since I’m using a non-reversible AC spindle.
1 Like
I would check the control knob. It’s probably a pretty simple pot, set up as a voltage divider.
Many of those take an input signal from 0-10V (12V is fine, anything over 10V will come up as 100% speed) so what you do is take a 12V PWM signal at 0-84% duty cycle and feed that to the control input. The duty cycle will simulate an average voltage which will be used to control spindle speed.
Feed it the power independently.
2 Likes
ok thanks
I have the same DC spindle…the pot on the psu is NOT pwm, if you look at the psu output wave form it is a really, really nasty chopped 80V supply. Your best bet if you really need to set up pwm control is buy yourself a better 80V supply and rig up a separate MosFet pwm board. I looked into this some time ago and decided the cost of a decent 80V DC step down regulator was prohibitive and so decided to just use the nasty variable psu manually and not use the PWM output from GRBL.
1 Like
ok, thanks Mike, good info 