fan2 always on at boottime 3.2beta1

  • Hey,

    after some time I updated my firmware to 3.2-beta1 and since then my "fan2" pin is always on at the start of the RepRapFirmware. I have a Duet 2 Ethernet board.
    This probably would'nt be a problem if a fan had been connected, but I have a laser connected.

    With only M950 F2 C"nil" command there is no change in this behaviour, but I managed to switch it off instantly after start with the command M950 P0 C"fan2".

    But I'd rather have it being switched off from the beginning as it was before the update for security reasons.

    Do you know what suddenly causes this behaviour? Should'nt be all pins switched off by default?


  • @LichtiMC Try putting S0 in the M106 for that fan (or if you have S1, change it to S0).

    The scenario where a fan might need to be fully on when power is applied is if power has been cycled for any reason, but a hot end is still hot. In that case, you want the fan to run as soon as power is applied to prevent heat creep causing a blockage, rather than wait for the Duet to boot (which if you have an SBC can be a can be a considerable amount of time).

  • Thanks for your suggestion.
    With "M106 P2 S0" in config the laser is still on for half a second or so.

    So I guess there's no possibility to set the pin to "default off" at start.

  • @LichtiMC said in fan2 always on at boottime:

    Thanks for your suggestion.
    With "M106 P2 S0" in config the laser is still on for half a second or so.

    So I guess there's no possibility to set the pin to "default off" at start.

    Possibly not. It used to be the case that the default was for fans to be off at the start but I think this was changed. The rationale being that if one has a thermostatic heat sink cooling fan and one cycled the power, possibly due to a failed print, then it could be some time before the fan started up again, which cause a hot end blockage due to heat creep. I could be wrong but I think that is why it is what it is.

    One thing to watch out for is that I have been reporting that my heat sink cooling fans do random "blips" on my machine using version 3 firmware. There doesn't see to be any pattern or logic to it and it has been present since the earliest 3.0 Beta firmwares up until 3.1.1. (I can't say if it's still there on 3.2.). I haven't noticed anyone else reporting this but unless you have a noisy fan and run the machine in a very quiet environment, you won't notice. For a fan, it isn't particularly a problem (unless you happen to have you fingers in it when it "blips") but if you connect a laser to a fan output, that would be a very different matter (you wouldn't want the laser bursting into life if you happened to be looking directly at it at the time).

    I'm not saying that you definitely will see this problem - just that it can and does happen with fans on my machine and has been doing every since I changed to version3 firmware some 14 month ago.

  • @LichtiMC would it be possible to move from a fan output to a heater output? Then it wouldn't be on as default

  • Moderator

    Can you post your full config.g please?

    Also post the results of M122 and M98 P"config.g" please.

    Fan2 should be off by default. It's only Fan1 that will run at power up as it was intended for use with the heat sink fan as deckingman mentions.

    Just to be clear, when you were running 3.1.1 the fan was off at startup, but when switching to 3.2 beta1 the fan2 will power on at startup briefly?

  • administrators

    Are you sure you mean Fan2 ? The fan output that is on by default on the Duet WiFi is Fan 1.

    Of course, if you are inverting the fan output to drive the laser, then off by default becomes on by default.

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