A thermistor is a resistor whose resistance changes with temperature. I have a silicone heater but it has two wires for the thermister.

I could only assume that the thermistor is sharing a wire with the heater?? That would be odd to be sure.

Maybe you could provide a link the the heater you are considering.

There are two receivers on the board. in analog mode the first one will give an output of 465, this will cause the z motion to slow down. What it is looking for is the second output at about 535. This is the one that should trigger the endstop.

You should be able to trigger these with your hand and see the output with an M119

Do you have more than one power supply? Or are you running your Duet Wifi off USB?

Otherwise I would think shutting off the AT power supply would shut down the entire system.

Please correct me if this is wrong.

So switching to PID did solve the problem.

You don't have to read the rest.

I am curious why this happens. On the SeeMeCnc forum one person attributed it to the hot end temperature changing, but my hot end temperature was steady. This is why I assumed there was a changing speed on the extruder.

I am also using a Bondtech extruder, so I wonder if it is more noticeable on a geared extruder.

Does it only happen when you run an SSR or Mosfet? Using these the current on the Duet for the bed heater is very small. Does it happen when running the heater through the Duet?

Anyway, I am finally getting decent prints (I introduced and fixed several issues when converting a Rostock V2 to V3)
I am loving the Duet Wifi.

I have the power supply at the base of the tool and the Duet in the top (converted Rostock Max V2 to V3) I measured the voltage at a terminal strip near the Duet (12 in wire between Duet and terminal strip) during bed heating and I did see a variation 12.01 to 12.05. The heater is in bang bang mode.
I have a meanwell 350W supply
From M122:
Supply voltage: min 11.8, current 12.1, max 12.2, under voltage events: 0, over voltage events: 0
=== Heat ===
Bed heater = 0, chamber heater = -1
Heater 0 is on, I-accum = 0.0
Heater 1 is on, I-accum = 0.4

I have 12 gauge wire from the PS to the terminal block and to the Duet

With the heater just turned on voltage at the terminal strip, Vin and Bed out all read the same at 12.05
I have 12.66 amps running to the bed through the Mosfet when it is on. There does not seem to be any current running on the control lines from the Duet to the Mosfet. I have 22 gauge wire for the control wires.

I hope this is the right place for this. I currently have one of the bigger mosfets delivering power to my heated bed controlled by a Duet Wifi. The bed heats great and everything works well. But I found when the heater cycles it does something that causes my extruder to run slower (?) I get a fairly regular thick and then thin extrusion pattern. When I turn off the heated bed, the effect goes away. Is there something I can fix here? I have verified all the wiring and connections.