Active FAN when heater is ON

  • Hello,

    i just installed my Duet2 ethernet (V1.04a) on my 3D printer here and I have faced a little difficulty here. Firmware version is 2.01

    I have a chamber heater with fans for spreading the heat around. The fans are on a separated connection.
    So right now I plugged my heater in heater E6 connection and my fan on E3 fan connection (on the DUEX 5 board).
    My problem is that I can't find a way to start the fan as soon as the heater is turned on. I could use a thermostatic control, but the thermistor is quite far away from the heater and i'm pretty sure I'll burn some stuff before getting a temperature rise to start the fan. Is there a way to start the fan on at full power as soon as I start the heater without having it on all the time?
    I don't want to simply have the fan controlled by separate G-code because there is too much risk of someone forgetting to turn it on.

    thank you and have a nice day

  • If you have a spare thermistor and open connector on the board, you could place it closer to the heater and use it to control the fan.

  • administrators

    I assume you are using an SSR to control the heater. How about connecting the fan and the SSR control terminals in parallel?

  • @phaedrux I could put it straight on the heater, but then I got 2 heaters...
    I don't love this solution, but it's a good backup.

    thank you for your help

  • @dc42
    Yes I can do this. I was more looking for a straight ON FAN when heating, but this seems safe enough.
    When I hooked it up to another output, I had problems with PWM.
    I'll test it and see what it does.

    thank you!

  • Hi guys,

    I did some testing this morning.
    in fact, what I see as a problem here is the remaining heat on the heater. It can be very hot when I stop heating with it.
    I need the fan to continue running for a few seconds once the heater is off to cool it down.
    I was so sure to have this kind of feature in the firmware, that i didn't check at all. This is the behavior I see as optimal:

    -> heater ON -> Turn fan ON
    -> Heater OFF -> Let fan ON for a delay then turn OFF

    It seems simple, but I can't seem to find a way to implement this. If anybody knows how to do this, then I would love to hear it. I see the solution with the thermistor can do this, but I thought it might be simpler to have it straight from the firmware.

    thank you and have a nice day

  • Hi guys!

    I'm also looking for solution for this problem. Can anyone help us?

  • @barcwik
    If you're happy with controlling it through c-code without feedback then: (however I'd rather put the fan under thermostatic control. Maybe explicitly starting it and switching to thermostatic control once chamber temperature has been reached.)

    -> heater ON -> Turn fan ON

    M106 P2 S255 ;turn on chamber/fan2
    M141 S50 ;turn on chamber heater
    M149 ;optional wait for chamber temperature

    -> Heater OFF -> Let fan ON for a delay then turn OFF

    M141 S0 ;turn off chamber heater
    G4 S10 ;wait 10 seconds
    M106 P2 S0 ;turn off chamber/fan2

    you'd also want to consider what happens when things don't go according to plan, and where to place the g-code

    Huh, didn't intend to tag Sim234, but seems it does so if you qoute and delete the refrence in the post.

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