Chamber heater wiring problem



  • I'm trying to set up a chamber heater. I have only 1 hotend, and my hotend is using the PT100 board. My bed is using a normal NTC thermistor. Both the hotend and the thermistor report and control the temperature, but I can't get the chamber thermistor to report anything but an error. I'm trying to use the second hotend thermistor and heater connectors for the chamber. I've got a normal NTC thermistor for the chamber temp.

    Here's a pastebin to the config.

    https://pastebin.com/fa7kJ9XP

    Any ideas?


  • administrators

    Do you get the error report on the chamber thermistor as soon as you start the Duet, or only when you try to heat the chamber?

    If it's right from the start, what reading do you get if you plug the bed thermistor into the E1 thermistor connector?

    You need to use M307 to force bang-bang mode, not M301 (that was for older firmware).



  • Ah, thanks, I'll switch to M307.

    It's in the error state immediately as i power it on. No change if I swap to the other extruder thermistor connector. I did execute X3 on the end of M305, which got me a temp display pegged at 88c, it doesn't really move.

    M305 P2 T100000 B3974 R4700 H30 L0 X3

    But X3 must not be right.


  • administrators

    Did you try plugging the bed thermistor into the E1 connector as I suggested? This would tell us whether it it the thermistor that is at fault.

    In the error state, what is the temperature reading?



  • I did, infact I tried a spare thermistor, then I tried with a new thermistor plugged into the spare channel so that it had a thermistor in each channel. Then I swapped them around. No such luck.

    @dc42:

    Did you try plugging the bed thermistor into the E1 connector as I suggested? This would tell us whether it it the thermistor that is at fault.

    In the error state, what is the temperature reading?


  • administrators

    And the temperature reading?



  • @dc42:

    And the temperature reading?

    I don't get a reading, it just says "error", unless I use the X3 parameter, in which case I get 88



  • @dc42:

    And the temperature reading?

    Oops, M105 reports T:20.3 B:21.8 C:-273.1


  • administrators

    It's been a while since I tested the chamber heater support, so I'll re-test it.

    You could a!so try plugging the thermistor into the E0 thermistor connector and using X1 in your M305 P2 command.



  • That also gave me an error state with a large negative temperature. I'm wondering if the combination of the first hotend temperature control using a PT100 is a factor?


  • administrators

    Use of a PT100 for the hot end shouldn't affect the availability of the E0 and E1 thermistor inputs.

    Perhaps you have a bad crimp connection on the thermistor? As you have a known working bed thermistor, try plugging that into the E0 or E1 thermistor connector, and your other thermistor into the bed thermistor connector, to see what readings you get.



  • Thanks! That was exactly the suggestion I needed to figure it out. Turns out the 5 thermistors I have on hand that came with connectors pre-crimped, something is wrong with them. None of them give a temperature reading, but plugging in the bed thermistor gives a sane chamber reading. Obviously that means something is wrong or unknown about my spare thermistors. An ohm meter also doesn't give a reading with them. Must have got a bad batch.



  • yup, all 5 crimped onto the insulation instead of bare wire, by the supplier.


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