Strange 24V fan behavior - won't turn off



  • Hi everyone,

    I recently installed a Duet Wifi into my Wanhao Duplicator 6. While I was at it, I switched my fans over to 12V Noctua for the board cooling and the hotend cooling block. I will describe how I wired those:

    I have a 24V-to-12V buck converter running off of the 24V Meanwell power supply. 12V output to the V_FAN pin where the fan voltage jumper would be. The 12V fans are plugged into their respective spots on the board. One is connected to and Always On spot (the board cooling fan) and the cooling block fan is plugged into FAN0. They both work as expected and are controllable. FAN0 is set to thermostatic control and works as expected.

    The 24V blower fan is plugged into the VIN pin of the fan jumper and the GND of the FAN1. This allows me to control it just fine EXCEPT that I can't seem to turn it all the way off like the cooling block fan.

    I checked my config.g to make sure that the blower FAN1 is not thermostatically controlled. It is not. I changed the starting PWM to S0. The fan still spins. I tried sending [c]M106 P1 S0[/c] and it still spins. When I send [c]M106 P1 S0.1[/c], it increases output slightly. [c]M106 P1 S255[/c] increases it all the way. So I am able to control it, just not shut it off.

    Is this related to the fact that I am mixing voltage with my fans, or unrelated?

    Here is my config.g:

    [[language]]
    ; Configuration file for Duet WiFi (firmware version 1.20 or newer)
    ; executed by the firmware on start-up
    ;
    ; generated by RepRapFirmware Configuration Tool on Mon Mar 05 2018 19:19:49 GMT-0700 (Mountain Standard Time)
    
    ; General preferences
    G90                            ; Send absolute coordinates...
    M83                            ; ...but relative extruder moves
    
    ; Network
    M550 PSuperDuplicator6         ; Set machine name
    M551 Preprap                   ; Set password
    M552 S1                        ; Enable network
    M587 S"" P""        ; Configure access point. You can delete this line once connected
    M586 P0 S1                     ; Enable HTTP
    M586 P1 S0                     ; Disable FTP
    M586 P2 S0                     ; Disable Telnet
    
    ; Drives
    M569 P0 S0                     ; Drive 0 goes backwards
    M569 P1 S1                     ; Drive 1 goes forwards
    M569 P2 S0                     ; Drive 2 goes backwards
    M569 P3 S1                     ; Drive 3 goes forwards
    M350 X256 Y256 Z256 E256 I0        ; Configure microstepping with interpolation
    M92 X1280 Y1280 Z12800 E1520         ; Set steps per mm
    M566 X1000 Y1000 Z12 E120        ; Set maximum instantaneous speed changes (mm/min)
    M203 X6000 Y6000 Z180 E1200    ; Set maximum speeds (mm/min)
    M201 X500 Y500 Z250 E250       ; Set accelerations (mm/s^2)
    M906 X1000 Y1000 Z1000 E1000 I60   ; Set motor currents (mA) and motor idle factor in per cent
    M84 S30                        ; Set idle timeout
    
    ; Axis Limits
    M208 X0 Y0 Z0 S1               ; Set axis minima
    M208 X200 Y200 Z185 S0         ; Set axis maxima
    
    ; Endstops
    M574 X1 Y1 Z1 S0               ; Set active low endstops
    M558 P0 H5 F120 T6000          ; Set Z probe type to switch and the dive height + speeds
    G31 P600 X0 Y0 Z1              ; Set Z probe trigger value, offset and trigger height
    M557 X15:185 Y15:185 S20       ; Define mesh grid
    
    ; Heaters
    M305 P0 T100000 B4138 C0 R4700 ; Set thermistor + ADC parameters for heater 0
    M143 H0 S120                   ; Set temperature limit for heater 0 to 120C
    M305 P1 X200                   ; Configure thermocouple for heater 1
    M143 H1 S280                   ; Set temperature limit for heater 1 to 280C
    M307 H0 A178.5 C673.1 D0.1 S1.00 V23.9 B0
    M307 H1 A237.3 C174.3 D5.6 S1.00 V24.1 B0
    M307 H2 A-1 C-1 D-1
    
    ; Fans
    M106 P0 S1 I0 F500 H1 T45      ; Set fan 0 value, PWM signal inversion and frequency. Thermostatic control is turned on
    M106 P1 S0 I0 F500 H-1         ; Set fan 1 value, PWM signal inversion and frequency. Thermostatic control is turned off
    M106 P2 S1 I0 F500 H-1         ; Set fan 2 value, PWM signal inversion and frequency. Thermostatic control is turned off
    
    ; Tools
    M563 P0 D0 H1                  ; Define tool 0
    G10 P0 X0 Y0 Z0                ; Set tool 0 axis offsets
    G10 P0 R0 S0                   ; Set initial tool 0 active and standby temperatures to 0C
    
    ; Automatic saving after power loss is not enabled
    
    ; Custom settings
    
    

  • administrators

    That behaviour is caused by the fan flyback diode. V_FAN must be the highest fan supply voltage in use. So change V_FAN to 24V and connect your 12V fans between the output of your buck converter and FAN- (or GND for the always on fan).



  • Thanks! Will do.


 

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