Quick question on Duet 2 / Duex electrical outputs



  • Before I screw things up badly, a quick sanity check :
    I understand that all outputs are active low. I was going to use the bed heater as the high voltage (24V). This will be used to run some SSR's. Obviously the heater terminals are ok with that voltage but are other outputs ok with that or should I elect to use a lower voltage as the high side of the SSR's ? The low side of the SSR's would be connected to whatever outputs I end up using, not sure which ones yet.



  • I've always just wired the low voltage side of the Solid-State-Relay to the heavy duty bed terminals. To be clear given the way your question is phrased: Two terminals on the SSR to two terminals on the bed screw connector. The SSR then gets 12 or 24V, which most of them support up to 30 something.

    Anyway, the 'simple' way works just fine. I have several printers running this way, the oldest for probably four years now.



  • Maybe I should give a bit more detail .... Yes, one SSR will be hooked to the heavy bed terminals and will in fact run the heater on the bed. I will have two more SSR's that I want to control via gcode - one for enclosure lights and one spare. The reason for the question - there is only a single high side going to all three SSR's and three separate low sides running to the control pins. I wanted to make sure that nothing would blow up if I had 24V on the control pins when thy are not active.
    Hope this makes sense.
    I see no reason why this should NOT work but thought it would be easier to ask then to replace stuff that had it's magic smoke come out.


  • administrators

    @jens55 said in Quick question on Duet 2 / Duex electrical outputs:

    Before I screw things up badly, a quick sanity check :
    I understand that all outputs are active low. I was going to use the bed heater as the high voltage (24V). This will be used to run some SSR's. Obviously the heater terminals are ok with that voltage but are other outputs ok with that or should I elect to use a lower voltage as the high side of the SSR's ? The low side of the SSR's would be connected to whatever outputs I end up using, not sure which ones yet.

    Which "other outputs" are you referring to?



  • @jens55 said in Quick question on Duet 2 / Duex electrical outputs:

    Maybe I should give a bit more detail .... Yes, one SSR will be hooked to the heavy bed terminals and will in fact run the heater on the bed. I will have two more SSR's that I want to control via gcode - one for enclosure lights and one spare. The reason for the question - there is only a single high side going to all three SSR's and three separate low sides running to the control pins. I wanted to make sure that nothing would blow up if I had 24V on the control pins when thy are not active.
    Hope this makes sense.
    I see no reason why this should NOT work but thought it would be easier to ask then to replace stuff that had it's magic smoke come out.

    If I understand this correctly, MAGIC SMOKE WILL COME OUT if wired as you describe.

    Wire the bed heater SSR to the screws that normally drive the bed heater, following polarity. Done.

    Wire the other two such that one side goes to +3.3V (this can be common between the two) and the other to the individual g-code controlled pins. Again, following polarity as marked on the SSR.



  • @dc42 said in Quick question on Duet 2 / Duex electrical outputs:

    Which "other outputs" are you referring to?

    LOL .... I haven't quite figured that out. The Duex has 4 uncommitted general purpose i/o pins, then there are fan outputs and endstops. I know I can use heaters and fans but thought I might see what my options were.



  • @Danal said in Quick question on Duet 2 / Duex electrical outputs:

    Wire the other two such that one side goes to +3.3V (this can be common between the two) and the other to the individual g-code controlled pins. Again, following polarity as marked on the SSR.

    Let me see if I have that correct. Any heaters can be used the way I envision. I would like to confirm if fans are also usable and are switched on the low side.
    The general I/O pins can not be used as I envision, nor can endstops. The I/O pins and endstops are also switched on the low side but can only have 3.3V on the high side ?



  • I am having troubles finding a full schematic for the Duet2 wifi and the Duex5. Could someone provide a link please?



  • I have decided to use the bed heater on the Duet2 wifi to supply power (24V) to my SSR's, the low end of the bed heater will control SSR #1 and I will use two of the heater outputs on the Duex5 as the additional SSR controls. I just would like to verify that all of these outputs use the same 24V rail so that I can use the 24V from the bed heater and not have to run lines for the high side of the two heaters I will be using.


  • administrators

    @jens55 said in Quick question on Duet 2 / Duex electrical outputs:

    @Danal said in Quick question on Duet 2 / Duex electrical outputs:

    Wire the other two such that one side goes to +3.3V (this can be common between the two) and the other to the individual g-code controlled pins. Again, following polarity as marked on the SSR.

    Let me see if I have that correct. Any heaters can be used the way I envision. I would like to confirm if fans are also usable and are switched on the low side.
    The general I/O pins can not be used as I envision, nor can endstops. The I/O pins and endstops are also switched on the low side but can only have 3.3V on the high side ?

    Correct.


  • administrators

    @jens55 said in Quick question on Duet 2 / Duex electrical outputs:

    I have decided to use the bed heater on the Duet2 wifi to supply power (24V) to my SSR's, the low end of the bed heater will control SSR #1 and I will use two of the heater outputs on the Duex5 as the additional SSR controls. I just would like to verify that all of these outputs use the same 24V rail so that I can use the 24V from the bed heater and not have to run lines for the high side of the two heaters I will be using.

    Correct.


  • administrators



  • Thank you for the assistance !


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