Additional fan on Duet 0.6?



  • Hi,

    I have a new duet wifi sitting ready to go for a large delta build I'm about to embark on, but in the meantime I have just finished a kossel sized build with a duet 0.6.

    Everything is working good, and it was useful to go through setting up the duet so I'm ready to go on the large build, my only wish is on the recently finished kossel with 0.6 board to have an additional fan output

    Basically on the kossel I have 2 fans on the effector, and a led ring, I have wired them all up together and tied them to the single FAN0 output and configured that as a thermo fan so they all come on above 80c.. it works fine, but it would be nice if I could have 1 fan (E3D cooling) and the ledlight configured with the Thermo option, and the 2nd fan configured as a gcode controllable cooling fan, without going to the extent of buying the duex4 expansion.

    If I could wire up one additional output, simlar to the FAN1 option on the 0.85 and use that as say thermo for the LED and for the main E3D fan, so doesnt need to be PWM just simple on/off based on hotend temp, and leave the 2nd fan connected to FAN0 as a pwm controllable cooling fan that would be perfect. I know the alternative is to leave the led & fan permanently on, but I'd really rather not, as I do prints overnight and while I am at work, so having a fan and led running for hours unnecessarily after the print is finished is not all that great.

    I understand there is GPIO pins available on the expansion connector, can I wire up say a common arduino driver module to one of those for the additional fan?

    Apologies if this has been answered already, I couldn't find the info (or at least not in a format I understood lol)


  • administrators

    That's all possible in principle but would need a firmware change. Probably the simplest approach would be to use one of the extruder heater outputs on the expansion bus to driven additional fan mosfet.

    An approach that wouldn't need any firmware change would be to attach a fine wire to the pin on the microcontroller that controls the second fan on the Duet 0.8.5, and use that to drive the mosfet.



  • Awesome thanks dc,

    Just to make sure I got it right - I should be able to look at the schematic for the 0.8.5 and identify the mcu pin that goes to FAN1, then find that same pin on the 0.6 and solder a fine wire to that, and that can control something like an arduino mosfet module?

    I've looked at the 0.8.5 schematic and it looks like there is a common pin PC4_PWML1 which is FAN1_PWM, this I have identified as pin 116 on the mcu, PC4_PWML1 also goes to pin 18 on the 0.8.5 expansion connector.

    The same pin 116 on the mcu labeled PC4_PWML1 on the 0.6 schematic goes to pin 25 on the 0.6 expansion connector

    So if I have it right, I should be able to control a external mosfet module (obviously wired correctly and suitable mosfet) using pin 25 on the 0.6 expansion connctor as FAN1 in firmware?


  • administrators

    I didn't realise that the mcu pin that is used as the second fan control pin on the 0.8.5 also went to the expansion connector on the 0.6. But if it does, then you could indeed connect the mosfet gate to that. I suggest a 1K series resistor, because that will protect the mcu in the event of the mosfet being mis-wired or shorted.

    Because the firmware will recognise your board as a Duet 0.6, you will need to use the I1 parameter in the M106 command to invert the PWM for the second fan. But I'll change the code in 1.17 RC3 to do the inversion automatically.



  • Awesome, thanks DC.

    I'll go ahead over the holiday break and try hooking one up, and let you know how I go



  • It Works!

    I need to print out a bracket for the mosfet module and run the wires neatly, but I can confirm pin 25 on the Duet 0.6 expansion wired to a basic arduino mosfet module works and is gcode referenced as M106 P1 (same as FAN1 on Duet 0.8.5)

    I had a basic arduino mosfet module on hand - the common cheap ones that are plentiful on ebay. After reading an old post from dc, here http://forums.reprap.org/read.php?13,596548 I removed the standard 1k to ground resistor and replaced that with a 10k, as well as adding a 1k resistor in series with the signal pin.

    As suggested dc, I needed to use the I1 parameter but aside from that its a fairly simple add-on, obviously a better mosfet module would avoid the resistor changes as well.

    Thanks for your help!


  • administrators

    @Crash69:

    It Works!

    I need to print out a bracket for the mosfet module and run the wires neatly, but I can confirm pin 25 on the Duet 0.6 expansion wired to a basic arduino mosfet module works and is gcode referenced as M106 P1 (same as FAN1 on Duet 0.8.5)

    I had a basic arduino mosfet module on hand - the common cheap ones that are plentiful on ebay. After reading an old post from dc, here http://forums.reprap.org/read.php?13,596548 I removed the standard 1k to ground resistor and replaced that with a 10k, as well as adding a 1k resistor in series with the signal pin.

    As suggested dc, I needed to use the I1 parameter but aside from that its a fairly simple add-on, obviously a better mosfet module would avoid the resistor changes as well.

    Thanks for your help!

    I am glad it worked. You should not need to use the I1 parameter if you upgrade to 1.17RC3 firmware.



  • @dc42:

    You should not need to use the I1 parameter if you upgrade to 1.17RC3 firmware.

    Confirmed,

    with 1.17RC3 loaded I no longer need to run the I1 parameter.

    Thanks again


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