DC Spindle from Bed Heater with PWM

timl

Hi,

Just got my Duet 2 Wifi (Firmware: 3.2.2) and getting am just everything setup to replace the GRBL control board in a small generic 3018 CNC until I can build a new machine.

I have one of these spindle motors: (https://www.amazon.co.uk/Genmitsu-GS-775M-20000RPM-Suppression-Electrical/dp/B08DTHDSMV/ref=sr_1_3?dchild=1&keywords=775+cnc+spindle&qid=1622126186&sr=8-3), before it was just directly connected to the control board.

Before I connect it all up I was just wondering if anyone could confirm that I will be able to do the same by simply connecting it to the bed heater output and controlling the speed with the PWM setting using the following code from the configuration file:

; Heaters
M140 H-1                        ; disable heated bed (overrides default heater mapping)

; Tools
M563 P0 S"Spindle"                   ; define tool 0

; CNC Mode and Spindle Settings
M453 C"bedheat" T0 R20000

Thank you,

Tim

droftarts

@timl Should be okay on the bed heater output, it's rated for 15A. There is this in that Amazon listing:

An alternative is to replace the stock power supply with one having greater current capacity (24V 8-10A), but that may burn out the controller with an abrupt 100% speed command.

Seems like you may need to ramp up speed to avoid burning out the controller. There's an example in the description on the Amazon page.

Looks like a nice little motor. I really must get around to finishing my CNC machine, one of these days...

Ian

o_lampe

@droftarts said in DC Spindle from Bed Heater with PWM:

Seems like you may need to ramp up speed to avoid burning out the controller.

Would it be possible to write a Meta Code macro in RRF to do the ramp-up?
How would you set this up?

define a GPIO pin as 'spindle-output' trigger
the trigger-macro reads the PWM duty cycle (that's the hard part of the equation)
the macro ramps-up the heater output
optionally sets another trigger, when motor is ramped up