Connecting a DA SSR



  • I am in the process of wiring up an very high powered AC heated bed, using a SSR to control it. The printer originally came with the DC bed connected to the Duet's GND terminal and the 12V from the PSU. I am wondering whether I reuse this wiring to connect my SSR. Or is there a good reason to find a place in the delta towers to run an extra wire connecting Duet bed + and SSR + ?

    Below, a simple drawing of how I plan to wire it.

    0_1534953869003_2018-08-22 18.02.48.jpg



  • Hi,

    If you wire it as shown the bed heater will always be on - I cannot imagine that is what you want.

    Check the normal bed heater connector on the Duet.

    One terminal is marked with a "-" symbol, the other with a "+" symbol.

    Connect those to the SSR control inputs, observing polarity.

    BTW what's a TCO?

    Frederick



  • @fcwilt said in Connecting a DA SSR:

    Hi,

    If you wire it as shown the bed heater will always be on - I cannot imagine that is what you want.

    Check the normal bed heater connector on the Duet.

    One terminal is marked with a "-" symbol, the other with a "+" symbol.

    Connect those to the SSR control inputs, observing polarity

    Why would the heater be always powered? The bed output of the Duet still opens and closes the circuit I imagine.

    BTW what's a TCO?

    TCO stand for thermal cutout, basically a temperature triggered fuse.



  • Mark you different GNDs to be more clear.



  • @sigxcpu As requested 🙂
    0_1534964708494_2018-08-22 21.03.46.jpg


  • administrators

    Yes, that will work.



  • @dc42 said in Connecting a DA SSR:

    Yes, that will work.

    Is there any consequence or disadvantage wiring it this way?


  • administrators

    None that I can think of.



  • @nxt-1 said in Connecting a DA SSR:

    Why would the heater be always powered? The bed output of the Duet still opens and closes the circuit I imagine.

    Because the way you had it drawn originally you had the - terminal of the SSR connected to a terminal on the Duet labeled GND. You had the + terminal of the SSR connected to +12, thus the SSR would be on as long as the power supply providing the +12 was on.

    Now you have changed the diagram to show using the BED- terminal which is NOT ground. Connecting that way will work.

    And as mentioned if it makes things simpler or clearer you can connect the BED+ terminal to the SSR + terminal.

    Frederick


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