Nominally voltage for 12v ATX supply while printing.

  • I'm trying to track down some issues I've had for some time and want to see if I should look into the boards more for possible damage / misconfiguration, or wiring, or perhaps a power supply issue.

    Here's my setup.

    Power Supply: Corsair CX600M
    Controller: DuetWifi + Duex5, Duex5 is missing a cap on of it's stepper drivers, which is currently unused. Long story, but I found it lying next to the board one day. Board is power from 5v standbye from atx.
    Display: 7", panelDue, see issue below.
    Hot End Heater: E3D 40 Watt - 12 volt - Heater and DuetWifi are power from a single 12v rail, fans are 12v
    Wiring to hotend: 16 gauge stranded copper.
    Bed heater: 12 volt PCB, insulated with 2-3mm silicone sheet, then 12mm of cork on bottom, 6mm of MIC 6 aluminum bed on top. 305mmx305mm dimensions. Driven by 2 x 12volt rails from power supply through a custom built mosfet driver, signaled using DuetWifi bed heater low side switching.

    Everything works fine minus the issues below otherwise heats up fast and the bed much faster than you'd think with 12 volt, thank you insulation. The typically voltage during printing is 10.8 - 10.9 with the bead heater off, and 11.1 with the bed heater on. Strange I know, could just be coincidence. Is 10.8 normal during printing?

    1. Print cooling fan surges when started, I have to issue a M106 F200 or similar to get it to run smoothly. Surging means attempt to run to full speed, then dropping to null and then repeating indefinitely. The timing of the surges is directly dependant on the percent of fan speed requested. The higher the speed requested, the shorter the idle duration between surges. %100 requested = no idle time and fan appears normal. Anything less than %100 requires M106 F200 or M106 F300, etc.. to remove the surging and run smooth. I do have this in my config.g with the hope it would resolve things, but to not avail, surging behavior remains: M106 P0 F200 B0.1 L0.05

    2. Heater faults on the hot end. I don't know if this config or wiring, combination of the two, weak heater, etc… But I get a lot of heater faults when starting up. I've modified what I believe to be the proper items to make it more lenient, but they still occur often. Here's my M570 if that helps: M570 S120

    3. PanelDue, in order to keep the backlight from flashing and keep display from glittering, I have to supply the DuetWifi with 5v over a separate USB supply.

    I've checked input voltages and do see on average .5-.7 higher input voltage than output, which I don't find terribly surprising. Since so many issues appear to be voltage related, I am curious if the operating voltage as indicated by the web interface is normal?

    I will post my full config.g below my signature as well.

    Any help / guidance would be greatly appreciated, normally I would track it down myself, but my hobby time is next to nil right now... 🙂



    ; CoreXY sample config file for dc42 Duet firmware

    M111 S0 ; Debug off
    M550 PBigRed ; Machine name (can be anything you like)
    M551 Preprap ; Machine password (used for FTP connections)
    ;*** If you have more than one Duet on your network, they must all have different MAC addresses, so change the last digits
    M540 P0xBE:0xEF:0xDE:0xAD:0xFE:0xED ; MAC Address
    ;*** Wifi Networking
    M552 S1 ; Enable WiFi

    M555 P2 ; Set output to look like Marlin
    M575 P1 B57600 S1 ; Comms parameters for PanelDue

    ; Machine configuration
    M569 P0 S0 ; Drive 0 goes forwards (change to S0 to reverse it)
    M569 P1 S0 ; Drive 1 goes forwards
    M569 P2 S0 ; Drive 2 goes forwards
    M569 P3 S0 ; Drive 3 goes forwards
    M569 P4 S1 ; Drive 4 goes forwards
    M569 P5 S1 ; Drive 5 goes forwards
    ; If you use an endstop switch for Z homing, change Z0 to Z1 in the following line, and see also M558 command later in this file
    M574 Z0 S1 ; set endstop configuration (X and Y and endstops only, at low end, active high)
    M574 X1 Y1 S0
    M667 S1 ; set CoreXY mode
    M350 X16 Y16 Z16 E16 I1 ; Set 16x microstepping with interpolation
    M92 X100 Y100 Z400 ; Set axis steps/mm
    M92 E809.42:300 ; Set extruder steps/mm
    M906 X1000 Y1000 Z1200 E1000 ; Set motor currents (mA)
    M201 X900 Y900 Z60 E1200 ; Accelerations (mm/s^2)
    M203 X18000 Y18000 Z1200 E2500 ; Maximum speeds (mm/min)
    M566 X600 Y600 Z60 E200 ; Maximum jerk speeds mm/minute
    M208 X326 Y305 Z635 ; set axis maxima (adjust to suit your machine)
    ;M208 X-22 Y-25 Z-0.5 S1
    M208 X-22 Y-25 Z-5 S1 ; set axis minima (adjust to make X=0 and Y=0 the edges of the bed)
    G21 ; Work in millimetres
    G90 ; Send absolute coordinates...
    M83 ; ...but relative extruder moves

    ; Z probe
    M558 P5 X0 Y0 Z1 T8000 F300 H10 ; Analog Z probe, also used for homing the Z axis
    ;G31 Z3.15 P500 ; Set the probe height and threshold (put your own values here) - .4 Hardended Steel / glass
    G31 Z0.15 P500 ; Set the probe height and threshold (put your own values here) - .4 Hardended Steel
    ;G31 Z.3 P500 ; Set the probe height and threshold (put your own values here) - .6 Hardended Steel
    ;G31 Z.25 P500 ; Set the probe height and threshold (put your own values here) - .8 Brass

    ; Thermistors and heaters
    ;*** You can use S and B parameters to define the parameters of the thermistors you are using
    M305 P0 R4267 H0 L0 ; Put your own H and/or L values here to set the bed thermistor ADC correction
    ;M305 P1 R4267 H0 L0 ; Put your own H and/or L values here to set the first nozzle thermistor ADC correction
    M305 P1 X200 ; Use PT100 Channel 1 for Heater 1 Temp
    M305 P2 R4267 H0 L0 ; Put your own H and/or L values here to set the second nozzle thermistor ADC correction
    ;M301 H1 P10 I0.10 D100 T0.50 S1.0 ; PID settings for extruder 0
    ;M301 H2 P10 I0.10 D100 T0.50 S1.0 ; PID settings for extruder 1
    M307 H1 A283.6 C117.8 D9.7 B0
    M570 S120 ; Increase to allow extra heating time if needed
    M143 S276 ; Limit temp to 276 for hot end

    ; Tool definition
    M563 P0 D0 H1 ; Define tool 0
    G10 P0 S0 R0 ; Set tool 0 operating and standby temperatures
    ;*** If you have a dual-nozzle build, un-comment the following 3 lines
    ;M563 P1 D1 H1 ; Define tool 1
    ;G10 P1 S0 R0 ; Set tool 1 operating and standby temperatures
    M572 D0 S0.05 ; Pressure advance settings

    ; Print Cooling Fan
    M106 P0 F200 B0.1 L0.05 ; Set PWM frequency to reduce high pitch whine.

    ;*** If you are using axis compensation, put the figures in the following command
    M556 S78 X0 Y0 Z0 ; Axis compensation here
    T0 ; select first hot end

    ; Setup PWM Fan outputs for LED light control
    M106 P5 H-1
    M106 P6 H-1
    M106 P7 H-1

  • I run mains on my bed so a little different to my setup, but my ATX runs at 11.95 volts consistently. I've got a large resistor (low value) on the 5v rail for regulation and I've connected the 3.3v sense to the 3.3v rail too. My system is reliable after these changes
    S3D will blip the fan on start up if you flick the gcode file. Why don't you supply 5 v from the ATX supply? I run my bltouch and other bits from the 5v rail parallel with that resistor I've got in my setup.
    FWIW I have a largish 12-24v DC to DC converter so I can run 24v to my steppers too. That works at treat.

  • administrators

    As @gavatron3000 says, you probably need a dummy load on the 5V rail to improve the 12V regulation.

    The PanelDue should run OK from the internal 5V regulator on the Duet, assuming you have that regulator enabled. It won't work so well if the only 5V power source to the Duet is via its USB socket from a PC.

  • 5v rail…. Ah, that might be my issue!

    One more tidbit of info, I leave the DuetWifi running all the time via +5vsb.

    Since I am using the +5vsb for powering the DuetWifi via the +5v ext pin, it makes complete sense that would not have the amperage to drive everything. According to the specs, +5vsb provides 3A max. +5v provides 25A max. The 3A from +5vsb feels on the edge of driving everything, hence why using +5v via USB works?

    So here's what I will do, tie in +5v 25A rail to the +5v ext in pin, leave +5vsb that's already there. When the DuetWifi isn't printing and the ATX supply is off, 3A seems to be enough to dimly light the 7" screen and keep the logic board running.

    Tie the sense lines to their respective rails. If needed will add a dummy load to +5v, but hoping the existing load will be enough and the sense lines connected to their rails will help.


  • That's basically how I have mine setup 5vsb only powers duet, 5v rail powers everything else. But I have a feeling that you have to have a reasonable load on the 5v rail but see how you go with what you've got

  • administrators

    3A is more than enough 5V power for a Duet WiFi + PanelDue. The built-in 5V regulator is only rated at 2A. However, the 5V external power is fed through a diode, so that actual voltage on the Duet's 5V rail will be more like 4.5V. There is another diode on PanelDue to protect against miswiring and prevent USB power to PanelDue from powering the Duet. So the backlight voltage will be reduced to about 4V, which probably isn't enough to run the backlight at full power.

    You could bypass the diode on PanelDue now that you know the wiring is right.

  • To finish off this thread. I rewired the leads from the Power supply to the duetwifi and duex5. Used the 12 volt connections from the atx female connector attached to the atx male connector from the PS and then some PCIe 12 volt lines for the bed and finished it off by attaching another 12volt plug to the sata / molex ports on the PS. The 5vsb remained for powering the DuetWifi.

    After that cleanup work and using additional 12v connections to the PS, everything is stable now and working as expected. 12v readings never dip below 11.5 and rarely go below 11.6/7 when printing, the bed is on and the hot end is on. I'd call this done.

    The only reamining issue is the part cooling fan that surges based on the requested fan %. The higher the percent, the shorter the interval between surging. A quick M106 F200 clears it up though.

    Thanks for your hep!


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