Remapping fan to heater output



  • In the 2.02 releases, it is possible to remap a fan to a heater output, in order to drive a Berd-air pump, using the A param.

    What is the exact syntax? For example, how do I define a tool fan using the first heater of the Duet? And the first heater of the Duex5? What should as use as P param, to avoid masking the real fan output (so I can still use it as normal fan output)?

    Thanks.



  • Hi Everyone,

    Sorry to hijack the thread as I would also like to know. I have not seen anything on the g code list. I also have another question about this. I am going to install a berd-air pump and was wondering if you are going to be using a heater output, is the inline thermistor still required or can the mosfet handle it?

    Kind Regards,
    Sam



  • Ok, I found in the code that logical pin 0-9 are heaters, and logical pins 20-... are fan channels.

    I guess heaters 0 and 1 are heaters on Duet board, and heaters 2-9 are heaters on Duex5.

    Is it the same for fan channels? Are 20-22 mapped to FAN0-FAN2 of the Duet? And 23-28 to FAN3-FAN8?



  • Heaters can handle up to 5A; I don't think berd-air pumps exceed that value. So, no thermistor needed.



  • @fma the std 12V Berdair style pumps can draw close to 9 amps on startup inrush current so be careful.



  • I bought a 24V chinese model; I'll check what is the maximum current...

    Thanks!



  • @fma 24V ones are fine I use them as well with no issues think they have around 27ohm resistance on the windings where the 12 volt ones are much lower (the one I measured was 2.7 ohms)



  • So I could even connect it to a standard fan output?



  • @fma I do but just for added safety I use a separate mosfet board as well but pretty confident a normal output would be fine (I used the mosfet board cos I already had it and was using the 12 v pumps before)



  • @dougal1957 I'd keep an eye on that misfit board, they have a tendency to misbehave. 🤣



  • Doh dyslexic fingers lol corrected now



  • Mmm, I just checked, and the resistance of my Berd air pump is 3.6 Ohm... Too low to connect on a heater output.

    So I need to put a thermistor to avoid too much current at start up. What model should I use?



  • @fma have you managed to figure out the m106 syntax to remap to a heater?



  • Changelog file says to use additional 'A' param to map a different output. See my post above for values.

    Note that I didn't make tests yet...



  • So something like M106 P3 A1?



  • That's what I understood.



  • @fma that sounds like one of those that was sold as 12-24 Volts pumps (Which is what I Got initially) the true 24 Volt ones are about 27 ohms IIRC in fact my spare measures 55 ohms they all seem to vary ie the QC on them is Crap



  • Oh well when my pump arrives I will give it a go. Thanks for your help


  • administrators

    @fma said in Remapping fan to heater output:

    In the 2.02 releases, it is possible to remap a fan to a heater output, in order to drive a Berd-air pump, using the A param.

    What is the exact syntax? For example, how do I define a tool fan using the first heater of the Duet? And the first heater of the Duex5? What should as use as P param, to avoid masking the real fan output (so I can still use it as normal fan output)?

    Thanks.

    Yes, there is a new A parameter in the M106 command, which is the logical pin number to use for the output (same as in M42 and M280).

    Caution: this is a temporary solution. The way this feature is used will almost certainly change in a future release, because we need something more flexible for Duet 3.



  • Thanks for the clarification.


 

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