Heater extruder with SSR



  • Hi everyone! Newbie here, so I get to the point:

    I'm using a prototype extruder with several heating elements, specifically 3x220W that are actually driven by a SSR due to their high power. This SSR has an input current of 7mA max with an input voltage of 12-24Vdc, I see that the duet2 design is rated to 5A per extruder heater connection: does this mean that I will have 5A going to my SSR (and then blowing it up)? If so, how can I connect the SSR without damaging it?

    Thank you!



  • 7mA max means it will take only 7mA to turn it off and it will not take more.
    But It is ok to connect it to a 5A output because Duet doesn't "force" 5A flowing through the device.
    5A output on Duet means you can connect a device with takes up to 5A, but the connected device determines how much current will flow through it.



  • @dragonn thank you very much for you kind reply!

    I'm working on this thing has my master thesis project so I'm worrying about pretty much anything, lol!

    So I have the feeling that there are going to be a few more of my posts/threads in the forum in the future, regarding various aspects of this project.

    Thanks again for the kind help!



  • @man_mar said in Heater extruder with SSR:

    3x220W that are actually driven by a SSR

    I am not an expert but may need to adjust the output PWM frequency of the Duet to work well with the (presumably) zero crossing AC SSR that you are using. The issue is that the duet can turn on the SSR any time but can turn it off only when the mains voltage crosses zero.



  • More and more SSRs have built in zero crossing detection, and will also only switch on at the zero crossing, effectively causing the minimum on period to be a half cycle.


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