Where is the best place to locate the thermistor for the heated bed?
I've seen a suggestion to put it through the center hold in the PCB and place it up against the glass printing bed. This makes sense in that you're reading the temperature of the actual pinting surface, but it also seems like you may end up with oscillation issues: The controller is sensing that the glass is not hot enough so even when the PCB reaches the desired temp it continues to drive it hotter and only shuts off once the glass is the right temp. When it shuts off, the PCB is hotter than the goal temp and continues to transfer heat to the glass so the glass gets too hot. There is a similar effect on the cool down due to the sensor being separate from the heating element.
Is this a problem? I have an axial thermistor that came for the PCB and I don't think it will fit through the hole in the PCB as it's too big. I could get one of the smaller ones, but if it is better or doesn't matter I'll just attach it to the center underside of the PCB.
BTW, I was planning on clamping the glass directly onto the heated PCB, so maybe the temperature difference is negligable.
Thanks,
Bret
