Wiring thermistors to GND instead of VSSA?



  • Hi to all,

    I'm sorry if this could seems to be a silly question. But I'm new to Duet and I'm going to use it instead of a RAMPS/Arduino in my new hypercube evo.
    I grouped all the connection in order to minimize the number of wires going to hot end, because I'm using a 12 pins connector to make it easier the hot end swap.
    At now termistor is wired to the same GND of the end stops and the always on fan.
    Is it possible to use the same configuration even in the Duet or I have to re configure the connector carrying even the VSS wire to the hot end?

    Thanks to all will help me.


  • administrators

    I really don't advise sharing ANY low voltage (e.g. thermistor) wiring with higher voltage (heater or fan) wiring.

    If your hot end heater and fans all run from the same voltage, you can use a common +VIN wire to feed all of them.



  • @dc42 thanks for your advice. That's exactly what I'm going to do, to use the same +Vin for heather and fan.
    In the board, what's the difference between gnd and vssa? Just the fuse?


  • administrators

    On the Duet WiFi/Ethernet, it's the VSSA fuse and the fact that VSSA goes to a point on the ground plane close to the MCU, to ensure that noise on the ground plane caused by stepper motors etc. doesn't interfere with the ADC readings from the thermistors.

    On the Duet Maestro, VSSA is also used to calibrate the ADC in order to improve accuracy, especially when using PT1000 sensors.



  • Thankyou so much!


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