Fan1 does not have enough voltage



  • I have a Noctua 40mm fan installed on my hotend, and when the Fan1 header is set to thermostat control, and the hotend temp is unplugged to force it to come on (i do this for testing, I am not actually ready to print yet) the fan bus comes on, but does not get enough power to start the fan spinning. If I give it a bump with my finger it will spin up and then its fine. What can i do to increase the power to that fan? I measure it at just over 10 volts on my hotend carriage. Is this a normal reading, or am i getting a voltage drop somewhere? Could I install a small capacitor somewhere near the end of the wire to provide a starting pulse?



  • see http://reprap.org/wiki/Gcodes#M106_in_RepRapFirmware in particular the B Parameter in the M106 command

    Doug



  • I see the B parameter, and that makes sense. However, its not a PWM fan? It only has 2 wires, hot + ground. I thought PWM fans always have 4 wires?

    Update: I added B1 to that line in config.g and rebooted. It did not make any noticeable difference.

    ; Fans
    M106 P0 S0.3 I0 F500 H-1 ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P1 T45 H1 B1 ; Set fan 1 to run anytime heater 1 is above 45C Blip at full power for 1 second
    M106 P2 S1 I0 F500 H1 T45 ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned on


  • administrators

    Test the fan by sending M106 P1 H-1 S1. This should make it run at full speed regardless of the hot end temperature.



  • @dc42:

    Test the fan by sending M106 P1 H-1 S1. This should make it run at full speed regardless of the hot end temperature.

    Ok, So i tried it. And the result is the same. The blades twitch a bit but dont start until i bump it. Then it runs fine. I just got my part cooling fan in, and im about to wire it up and test it too.



  • Just over 10v sounds like something is quite wrong in the wiring/PSU, should be a lot closer to 12v.



  • Thanks for the input yall. i just measured it again, and at the Duet i get 11v and at the fan i get 5v this time.
    that means my wire is way to thin… =( back to the drawing board,



  • 11v at the Duet is low too - would recommend re-evaluating all wiring and connections. Shouldn't see a drop of more than a quarter volt anywhere.



  • @elmoret:

    11v at the Duet is low too - would recommend re-evaluating all wiring and connections. Shouldn't see a drop of more than a quarter volt anywhere.

    With all fan wiring unplugged, i read 11.85v on the fan1 header. Definitly a wiring issue. too long a run to be using cat5 wires. I will have to dismantle and go with 22 or 20 guage.
    The total run length is around 4 feet from fans, thru the cable chain, down the inside of one leg, and routed around to where the Duet is mounted. I havnt tried to power up the Z bed levelling sensor, but i bet it would wind up with the same issue. So its time to rewire.


 

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