Spindle speed control

TonyPagett

I want to add a PWM output from my Duet3D board to control a VFD and spindle.
I have a PWM to voltage (1-10v) board that converts a PWM value into voltage. (5v =50%, 10v=100% etc) that connects to my VFD.

QUESTION:

Can I use heater 4 (on pin 13 of the Duet board) as a PWM output by using the following in my post processor?

M307 H4 A-1 C-1 D-1 -- to disable heater 4
M42 P4 Snnn --to send a PWM value

jay_s_uk

What firmware version are you on?
Have you seen M453 which sets the machine in CNC mode to allow the use of M3 and M5?

A Former User

my Duet3D board

presume you have a duet 2 wifi or duet 2 ethernet? running reprapfirmware v2.x?

Can I use heater 4 (on pin 13 of the Duet board) as a PWM output by using the following in my post processor?
M307 H4 A-1 C-1 D-1 -- to disable heater 4
M42 P4 Snnn --to send a PWM value

by persuming its a duet 2 you're refering to the 50 pin expansion header, that should give you a 3.3v pwm signal, but you might want to use

https://duet3d.dozuki.com/Wiki/Gcode#Section_M453_Select_CNC_Device_Mode
https://duet3d.dozuki.com/Wiki/Gcode#Section_M3_Spindle_On_Clockwise_CNC_specific_Laser_on_Laser_specific

instead of M42, also beware in some case the firmware invert the heater output pins

TonyPagett

@jay_s_uk
I do use M453 cnc mode. How do I assign a particular pin as a PWM output?
Would it just be a case of M453 P4 R24000 (max spindle speed) and then M3 S255 for max speed?

jay_s_uk

depends of the version of the firmware you are on.
Whats the output from M115?

TonyPagett

@jay_s_uk
v2.03

I have just been looking at using a fan output instead. M106 P2 Snnn.
Would this work?

jay_s_uk

@TonyPagett said in Spindle speed control:

Would it just be a case of M453 P4 R24000 (max spindle speed) and then M3 S255 for max speed?

If your standard heater ports are available I would just use one of those.
And yes, it would be as you've suggested, just using the right pin number (and freeing up the pin)

I would also consider upgrading to RRF3 when a CNC orientated version of DWC is released as you can also add a direction pin rather than jumpering forward to ground.

This is a helpful page. https://openbuilds.com/threads/workbee-cnc-w-duet2-and-chinese-spindle-control.14004/
Also connect the grounds on the VFD to a ground on the PSU for the duet (but this would be a DC ground and not an AC ground).

I use 3.2 beta 2 on my machine and I have this PWM converter https://www.amazon.co.uk/1-3KHZ-Voltage-Module-Digital-Converter/dp/B0789738RC/ref=sr_1_3?crid=AAYEZCBCA2WZ&dchild=1&keywords=pwm+to+analog+converter&qid=1603813874&sprefix=pwm+to+ana%2Caps%2C160&sr=8-3

TonyPagett

@jay_s_uk
Many thanks. I will do a few tests using various options.
FYI, my VFD allows me to disable the REV direction (which I have already done to prevent broken end mills!!)
Many thanks again.