SSR bed heater + Duet2 config



  • Hello!

    Background: (I'm building a railcore). I'm trying to setup an SSR controlled main voltage bed heater, but I cannot get the SSR/bed heater to power on.

    Board setup: Duet2Wifi+Duex-5, Firmware 3.1.1 (2020-05-19b2)

    SSR setup: Output side: Mains + bed heater. Input Side:Duet Bed heater(-) connected to ssr input(-) and Duet bed heater(+) connected to input(+).

    I have minimally confirmed that the SSR works (applying a 5V potential across the input side turns on an indicator light on the SSR). However, when connected to the Duet2 this indicator light never turns on (i.e. when bed heater is set to active and set temperature is elevated). This suggests to me this is probably an issue with how I have my board configured. Hopefully a typo or left out GCode! I've looked at it for hours along with others' configuration files, and can't find what I've missed. Maybe someone could take a look at my config file and see if anything stands out as wrong or has troubleshooting suggestions?

    Thanks!

    heater relevant config.g:

    ;heaters
    M950 H0 C"bedheat" Q10 T0
    M950 H1 C"e0heat" T1
    M950 H2 C"e1heat" T2
    M140 H0 ; the bed heater is heater 0
    
    M570 S360                                  ; Print will be terminated if a heater fault is not reset within 360 minutes.
    M143 H0 S150                                ; Maximum H0 (Bed) heater temperature
    M143 H1 S400                               ; Maximum H1 (Extruder) heater temperature 
    M143 H2 S250
    M140 S0 R0                           ; Standby and initial Temp for bed as "off"
    
    

    full config.g
    config.g



  • I can't see anything specific that it doesn't like.
    I would say that M140 needs to come before M143 when setting up a bed.

    Can you post the output of

    M98 P"config.g"
    

  • administrators

    I suggest you use a multimeter to measure the voltage across the bed heater output of the Duet, to check that it has voltage when you turn the bed heater on, and to confirm that you have the correct polarity at the input to your SSR.

    Note, the heater will fault after a few seconds of being turned on, if the thermistor doesn't confirm that the temperature is rising.



  • This may be silly but I ran into the same thing and realized that I had switched the polarity on the wires. You may want to make sure you got + going to + and - to - on from the board to the SSR.



  • M98:

    11/30/2020, 7:08:09 PM 	M98 P"config.g"
    Warning: Heater 0 appears to be over-powered. If left on at full power, its temperature is predicted to reach 295C
    Warning: Heater 2 appears to be over-powered. If left on at full power, its temperature is predicted to reach 533C
    Warning: Macro file config-override.g not found
    

    Voltimeter: Good call. This seems to be the issue. I connected appropriate probes to the heater+ and - duet ports and observe 0.15V voltage regardless of the heating state in the web panel. Not sure why there is a background voltage, but this is obviously not sufficient to trip the 4V cutoff of the SSR. Is there something in my configuration that would lead to the voltage being so low/not working? I measured the voltage directly at the connector ruling out a wiring problem. If it is a duet hardware issue, is it possible to just run the ssr off of one of the 5 extruder heaters on the duex board?


  • administrators

    @ginoocch said in SSR bed heater + Duet2 config:

    If it is a duet hardware issue, is it possible to just run the ssr off of one of the 5 extruder heaters on the duex board?

    Yes it is.

    Is the 15A bed heater fuse on the Duet intact?



  • I didn't even know that SSR had polarities.

    I was lucky 2 times in a row 😰



  • @dc42 said in SSR bed heater + Duet2 config:

    Is the 15A bed heater fuse on the Duet intact?

    Yes, its fine.

    Switching to E02 on the duex worked great, and now I get a fun light indicator 😁 Thanks for your help!


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