External Reset Switch



  • Hi,

    Is there an "approved" place to connect an external, normally closed, reset switch?

    Thanks.

    Frederick


  • administrators

    Do you want to hard reset the board? If so the reset pin is on the expansion header on pin 44.
    https://duet3d.com/wiki/Duet_WiFi_wiring_diagrams

    That said you may prefer to use a soft reset such as running M112 gcode via a trigger:
    https://duet3d.com/wiki/G-code#M581:_Configure_external_trigger

    This page on the wiki may help:
    https://duet3d.com/wiki/Connecting_an_Emergency_Stop_button



  • @T3P3Tony:

    Do you want to hard reset the board? If so the reset pin is on the expansion header on pin 44.
    https://duet3d.com/wiki/Duet_WiFi_wiring_diagrams

    For this option I need to bridge pin 44 with gnd? Or another pin?


  • administrators

    Yes pull the pin to ground



  • Thanks for the info.

    I was thinking of duplicating the function of the reset button on the board but I have a Duex5 so I cannot use the expansion connector.

    Is there any other place to connect to?

    Frederick


  • administrators

    My recommendation would be to use the external trigger to trigger M112/M999 as explained in the link because there is not another location that the reset wire is exposed.



  • @T3P3Tony:

    My recommendation would be to use the external trigger to trigger M112/M999 as explained in the link because there is not another location that the reset wire is exposed.

    Thanks much - will give that a try.

    Frederick



  • Can someone specify a bit more in detail what is going to happen AFTER executing an M112 midprint or mid-homing or something else?
    I assume, every command in the bugger is getting executed UNTIL the internal gcode buffer reached the point where M112 is listed? This way, it is more like a delayed stop?! (just assuming)
    What if M112 is executed while homing? Or a long G1-move?


  • administrators

    M112 may be delayed a little depending on how busy the processor is. Whereas the reset button stops everything immediately and restarts the Duet.



  • Does "a little" mean: "after the currently executed commands are done"? Or does the DUET interrupt mid-command?


  • administrators

    M112 will interrupt mid command. But until I migrate the firmware to RTOS, it may have to wait for an SD card or network transfer to complete before the processor sees the M112 command.



  • @fcwilt:

    Is there an "approved" place to connect an external, normally closed, reset switch?

    Fredrick,

    Is this intended to be a "Reset" or an "E-Stop" in the TRUE sense of e-stop? True e-stops, as found in the machine shop floor CNC world are quite rare on 3D printers.

    Even if the switch looks like below, it is often wired up as a "Stop" not an "E-Stop". What is the difference?

    • "Stop" signals something to stop. Most of the time, this works. However, it is easy to see circumstances where it might not: What if the firmware is off in an interrupts disabled loop, that happens to toggle one of the motor driver 'step' pins? Or whatever. It does happen…

    • "E-Stop" forces it, no matter what the machine state, including totally hung software, firmware, and most of the hardware. As an example, many "E-Stop" on CNC are wired into a board with gates that inhibit the stepper driver enable lines. Pure hardware, and 'very far downstream' close to the motion.

    If you want a true e-stop on a piece of hardware that doesn't have that input, here's one way to get there:

    My CNC E-Stops that are on boards like the Tiny-G that did not truly accommodate E-Stop in the hardware… those E-Stop switches are wired to cut the power provided to the controller board (and motor drivers logic side, where external drivers are used). Hitting the latching E-Stop physical switch stops the machine INSTANTLY, within the realm of friction and inertia. The motors certainly do not take even one more step.

    Switches like this, wired in a loop with using the NC side of the switch, with that loop providing power to the controller board:



  • In the individual case of the Duet, the full power for all drivers, bed, etc, (the main big green VIN with screw connectors) should NOT pass through the e-stop loop.

    Instead, set the jumper "Ext 5V EN", and then use the e-stop loop to break the 5v flowing into the separate (pin) connector (labeled "EXT 5V" in duet wiring diagrams).



  • Why not fit an emergency stop yellow switch with big button in the mains supply to the machine? Or use an rcd plug placed next to the machine which has a test button, this is even better as it breaks live and neutral and offers protection from ground leaks, shorts and current imbalance all at once. If you have power fail/resume correctly setup you can potentially restart your print once the problem is resolved.



  • @DjDemonD:

    Why not fit an emergency stop yellow switch with big button in the mains supply to the machine? Or use an rcd plug placed next to the machine which has a test button, this is even better as it breaks live and neutral and offers protection from ground leaks, shorts and current imbalance all at once. If you have power fail/resume correctly setup you can potentially restart your print once the problem is resolved.

    Because cutting the mains will allow the machine to operate for several seconds. This SHOULD be a shutdown, as the board senses power loss, etc. And your point about resume is valid if everything is set up correctly.

    But… that is a "Stop", not an "E-Stop". Which may be fine for 3D printers. And it is certainly your decision.

    At the same time, make an informed decision: If you want true E-Stop, freeze the machine instantly, not one more step, then cutting the mains misses that mark.


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