using M3 command to open and close a switch

[anagh]

Hello, I have a duet 3. I want to use the M3 command to open and close a switch. Initially, I tried to use a relay by connecting it to a fan output (out3). My hope is to be able to use the output3 voltage to switch the relay and close the switch. Here is what I used in config.h for that.

M950 F0 C"out3" Q100 ; create fan 0 on pin out3 and set its frequency
M106 P0 S0 H-1 ; set fan 0 value. Thermostatic control is turned off
M563 P0 S"Spindle" F0
M453 S"Spindle" P"out3" R12000 F2000 T0

I read somewhere that the P parameter for M453 has been discontinued. When I remove P parameter, the "Spindle" in the DWC becomes inactive

But when I send M3 S10000 command and connect a multimeter across the out3 pin, I don't get any voltage. Can anyone help me with this. The firmware I am using is 3.1.1.

If there is any other better way to open or close a switch with M3 command (I can not use any other command), please let me know. Thanks!

[Phaedrux]

Why must you use M3? I don't understand the requirement.

Rather than treating it as a fan, why not treat it as an i/o pin and switch it with M42.

https://duet3d.dozuki.com/Wiki/Gcode#Section_M42_Switch_I_O_pin

[anagh]

@Phaedrux This is mainly due to legacy reasons. My Gcode has several M3 and M5 commands. If I decide to switch them with M42, it will be cumbersome. Also, I use one more machine with a different controller which uses M3 and M5. So I will have to maintain separate sets of Gcodes for both machines.

I can use M42 as a last resort. But preferrably, I would like to use M3 and M5.

[A Former User]

Does your M3 specify an fixed RPM with the S parameter? If so you should be able to use just M435 C"out3" Rn where n is the same RPM you use for M3.

@anagh said in using M3 command to open and close a switch:

M453

in 3.2 M435 has a dedicated pin for on/off shouldn't that do what you need it to do regardless of speeds?

https://duet3d.dozuki.com/Wiki/Gcode#Section_M453_in_RepRapFirmware_3_2_and_later

in either case skip the M950 and M106 not sure you need M563 either.

[anagh]

My M3 does not specify a fixed speed. For the other controller, my Gcode just has M3 without the S parameter.
I will try using just M435 and let you know how it goes. Thanks for your help!

[anagh]

@bearer I tried using M453 C"out3" R5000 in config.h. After that when I send the M3 S5000 command, I get a message saying "M3 S5000 command not supported in machine mode FFF". When I just M3, it accepts it but I don't get any voltage across out3 and after that when I send M5, I get the same error message of command not supported.

Am I doing something wrong here?

[A Former User]

@anagh said in using M3 command to open and close a switch:

not supported in machine mode FFF

sounds like M453 didn't put the firmware in cnc mode

what do you get if you query with M450?

https://duet3d.dozuki.com/Wiki/Gcode#Section_M450_Report_Printer_Mode

[anagh]

In hindsight, the error is funny. In your earlier message, you mentioned M435 instead of M453. So I typed in M435 instead of M453 even though I knew I had to use M453.
I corrected that and now it is working. I have to use M3 Sxxxx to turn on the switch instead of just M3 like I did for the other controller but I will live with it.
Thanks a lot for your help.

[A Former User]

lol, sorry - don't trust random strangers on the internet at 3am

anyways, as long as the other controller doesn't complain about he S parameter then I'd say thats the way to go then.

[Alpenprinter]

I have a quite similar Problem:

I want to switch a on/off realy to switch the spindle via the M3/M5 command.

The relay is connected the fan port 7 of a Duet3 board.
I configured the following lines:

"M453 P7 S0 T0 C"out1+out7+out2" ; set CNC Mode"

Result:
"M3" does not switch the relay, but "M3 S1" does.
"M5" stops the spindle, as intended.

How can I configure the board, so I can switch the spindle with "M3" only, without M1, because this is how the gcode ist generated my the postprocessor?