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    Adding Third Hotend Cheaply

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    Duet Hardware and wiring
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    • binterryan76undefined
      binterryan76
      last edited by

      I wand to add a third hotend but i dont want to buy the whole duex expansion board just for one more thermistor and heater. Is there a way i can add those components more cheaply like with a solid state relay hooked up to the heater pins on the expansion headers (to reduce the current requirements through the pins)? The thermistor is low current enough that would it be possible to plug it directly into the expansion headers? Thanks.

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      • dc42undefined
        dc42 administrators
        last edited by

        Yes that's possible. There is a wiki page about adding external drivers. You can connect the control terminals of an SSR between +3.3V and one of the extra heater signals on the expansion bus. The signal level is 3.3V, which is enough for most commercial SSRs but might not be enough for the cheap ones on AliExpress etc. unless you reduce the value of a resistor on the SSR.

        You will need to connect a 4K7 resistor between the thermistor input and the VREF pin on the expansion bus.

        Duet WiFi hardware designer and firmware engineer
        Please do not ask me for Duet support via PM or email, use the forum
        http://www.escher3d.com, https://miscsolutions.wordpress.com

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