Control of the temperature of the printing chamber

  • I need to be able to control, using PWM, 2 solid state relays that control the resistance of the bed to 230 AC and the resistance of the printing camera this also use 230 AC.

    1. I think I need the extension board to have more PWM outputs but I don't know if this extension is only compatible with Duet 2 or also with Duet 2 Maestro

    2. On a Duet 2 or Duet 2 master board, how many PWM pins are available?

    3. Is it possible to reassign the pins in the firmware? For example, the output of the bed heater to me is not useful because I go to 230 AC, I need to assign a PWM of 5V DC to control the solid state relay.

  • @Javier-M Regarding you point#3, you most certainly can connect an SSR to the bed heater output to control a 240V bed heater. IIRC, by default the PWM frequency for the bed heater output is 10Hz, mainly because it is "kinder" to SSRs.

  • administrators

    Most SSRs accept 3 to 32V control voltage input. Such SSRs can be connected to any of the following on the Duet:

    • Any heater output (including the bed heater output)
    • Any fan output (you would need to use RepRapFirmware 3 to be able to reassign a fan output as a heater output)
    • On Duet WiFi or Duet Ethernet with no expansion board connected, any of the 5 heater outputs on the expansion connector. They are active low, so connect the SSR control terminals between the output and +3.3V.
    • On the Duet Maestro, to the MOD pin of the Z probe connector, if you are not already using that pin (e.g. to control deployment of a BLTouch). Again, you would need to run RepRapFirmware 3 to be able to reassign this pin to be a heater.

  • These two SSRs that you want to control, why two? Do they need to be independently controlled? Or are they different phases of electrical power? Or some other reason?

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