Configuring chamber 'heater' with no actual heater

achrn

I have a MB6HC based printer with an enclosure, but no active heating (obviously it gets warm in there from bed and nozzle).

Board: Duet 3 MB6HC (MB6HC)
DSF Version: 3.3.0
Firmware: RepRapFirmware for Duet 3 MB6HC 3.3 (2021-06-15)
Attached Raspberry Pi 4

I like to see what the temperature in the enclosure is, so there's a thermistor in there for that. I find it convenient to see that on the front page, so I've defined a chamber heater on an output that's actually not connected to anything (out3, as it happens):

M308 S2 P"temp3" Y"thermistor" T4701 B4266 C1.048787e-7 A"chamber"
M950 H2 C"out3" T2
M141 H2

I've noticed that if I don't execute any M307 at all on the heater I can actually set temperatures on my chamber 'heater' and let it go active, without triggering a heater fault.

This is potentially handy, because I also have a fan that vents the chamber (which cools it) and I could make that refer to the chamber set point (via daemon.g). However, I won't bother if this doesn't-fault behaviour is accidental and is going to disapear now I've highlighted it. So my question is: is 'no-M307-means-no-heater-faults' a behaviour that's likely to stay around?

An alternative is to set chamber temperature but always set the chamber heater off. I'd quite like to set the temperature from gcode, and I can't find a way to set the chamber heater status to off (but have a temperature set) from gcode - is there one I've missed?

(I found some past discussion that says you can't set chamber heater state other than setting it to a temperature of 0 if you want it off and debated whether there was any use for such a function.)

dc42

@achrn you don't need to define a heater using M950. Just define the sensor using M308, then click on the Extras link in the tools/heater status in DWC to include that temperature in the graph.