Duet2 WiFi using heater pins for fans?



  • What I have:
    Duet2WiFi
    Firmware 3.1.1 (just upgraded from 2.05.1)
    24v power supply
    12v buck converter
    Fans 0,1,2 being supplied 12v from converter

    My fan2 is inoperable (probably mosfet) so I need to add two fans.

    Following this example from the wiki
    M950 F3 C"heater2" Q100 ; Fan 3 is connected to heater 2 pin, PWM at 100Hz
    my config.g contains this under fans

    ; Fans
    M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency
    M106 P0 S0 H-1 ; set fan 0 value. Thermostatic control is turned off
    M950 F1 C"fan1" Q500 ; create fan 1 on pin fan1 and set its frequency
    M106 P1 S1 H1 T45 ; set fan 1 value. Thermostatic control is turned on
    M950 F2 C"fan2" Q500 ; create fan 2 on pin fan2 and set its frequency
    M106 P2 S0 H-1 ; set fan 2 value. Thermostatic control is turned off
    M950 F3 C"heater5" Q500 ; create fan 3 on pin heater5 pin, and set its PWM frequency at 500Hz
    M106 P3 S0 H-1 ; set fan 0 value. Thermostatic control is turned off

    I have the power connected to same 12v converter as the onboard fans and the negative connected to the heater5 pin. I also tried C"ext.heater5" but had no better results. The fan runs continuaously and cannot be controlled by M106 commands. i.e.

    M106 P3 S0 or M106 P3 S155, or M107 P3

    Can someone point out my error?
    Thanks


  • administrators

    You didn't mention a DueX, so I assume you don't have one. The exp.heater5 pin on the expansion connector is a low-current 3.3V-only pin, so it can't control a fan directly unless you use an external driver of some sort. You may well have damaged it if you connected a fan between it and +12V.



  • Can i use any of the pins on the expansion connector for a fan or laser control?



  • @GeorgeM said in Duet2 WiFi using heater pins for fans?:

    Can i use any of the pins on the expansion connector for a fan or laser control?

    they're all* have the same limits, if you need to sink or source any amount of current the answer is probably "no, not without a buffer or driver inbetween".

    iirc most of the pins are in the 2-3mA range, so pretty much noting that isn't a very high impedance input is a no-go.

    *some have a little more than 2-3mA but still not enough to drive anything like a fan



  • So to go off in a little bit of a different direction. Can I use one of the heater pins to control my laser. It will operate on 5 volts. Do I set it up as a servo as this example:

    M950 P0 C"exp.heater5" ; create output/servo port 0 attached to heater 5 pin on expansion connector

    Will doing it that way give me PWM control?



  • it would totally depend on how much current you need to sink or source into the laser, and if the pin would ever see 5v or not - also if 3.3v is sufficient to trigger the 5v input.

    so it depends on the laser



  • The laser control can work on up to 24v. Here is the the laser driver specs:

    Specifications:
    Specification HCDBSAFDA2_5AMP
    Current Source Range: 0 – 2.5 Amps
    Current Limit Jumper Settings: 0.5, 1.0, 1.5, 2.0, 2.5 Amps
    Compliance Voltage w/12V adapter: 8 volts
    Current Resolution: 0.1%
    Current Adjustment: Analog Trim Pot
    Current Range Accuracy Always greater than limit, no more than 15%
    Laser Diode Protection: Soft Start, Reverse Voltage, Current Limit, Thermal Shutdown
    Integrated Safety Features Laser Enable Key Switch, Integrated Laser Interlock, Power off Reset, LED Indicators
    AC Adapter Input Voltage: 100 – 240 VAC
    Control Signal Digital Isolation Voltage: 4500 Vrms
    Minimum Control Signal ”Turn On” Voltage: 2.8 Volts
    Control Signal Maximum Voltage: 24 Volts
    Control Signal Maximum Current: 50 ma
    Control Signal Maximum Frequency: 5KHz
    Connectors: Screw Terminal and Molex Mini-Fit Jr™ Connectors



  • @GeorgeM said in Duet2 WiFi using heater pins for fans?:

    specs

    insufficient data. yes it will trigger at 3.3v, but no info on impedance or source/sink current at 3.3v, only max current. 2.8v logic threshold leaves very little room for adding a series resistor to limit the current.

    i'd measure the current at 3.3v or go with a buffer for good measure.


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