DuetWifi: 5V super capacitor to keep power on through a power dip



  • A little bit of background information on the setup, for which I need to do some calculations:
    The printer chassis is the Wanhao D5S series (single extruder, though replaced with a Titan and E3Dv6). 5" PanelDue screen used as main operating interface (WiFi used as backup and to transfer files). I will be supplying its power from a 24V Meanwell power supply (350W, since it will also run a ~160W heatbed).

    The questions I have is regarding 2 DuetWiFi/Ethernet features: The Power Supply on/off; and the saving in case of power failure.
    I will be using a solid state relay in parallel to the power switch (which supplies Mains to the Power Supply), with its 5V trigger running on the PS_ON wiring, this is to allow the printer to shut itself down in case of Emergency Stop and when done with a print (I know to not print unattended, at least for longer times, but sometimes I am outside when it needs to complete, and then shut itself down).

    In my case, I have a scenario I want to protect my prints/printer from:

    1. Power dips, brown-outs. Basically our electricity supplier does not always provide very stable power and every now and then (luckily not too regularly) the power takes a dip. Most of the time this last less than a second, but to be safe I need to keep the printer on for about 3-4 seconds after losing power (hopefully it regains power, and can simply resume).

    In order for the printer to stay on (without switching itself off, on power failure), I think I need a way to keep 5V going into the printer from the 5V at the PS_ON connector (its GND and 5V pins), which is where I am thinking of using a super capacitor (5.5V, 1F, or more). Obviously the capacitor needs a charging resistor to not overpower the regulator, and using a diode, I can bypass the resistor when it should discharge to keep the logic going.

    Can the DuetWiFi automatically continue printing, if power is restored quickly (in stead of requiring manual intervention)?
    I know ideally I should have it on a UPS system, but that is just not financially possible at this time (though in the pipeline for later).


  • administrators

    Hi

    Have a look at this wiki page
    https://duet3d.com/wiki/Setting_up_to_resume_a_print_after_a_power_failure_or_planned_power_down

    The Duet has the capacity to pause a print when the VIN drops below a set level, save the state and then that state can be used to resume.

    Cheers

    Tony


 

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