Safety processor

  • It's not directly Duet related, but can add some more safety to a hot printer with sometimes bad and smoking connectors or cheap chinese powersupplies with burning inrush NTC's …
    I had this thing already in mind for some time now and wanted an independent security device that could cut all high power stuff in the printer upon detection of a potential danger.
    The danger my wife has in mind is fire ....
    So this one detects smoke, CO2 and some other gases and can detect high temperatures with 2 independent detector units.
    I want every user to be aware of that and consider this as my contribution to the community.
    Think about it and feel free to use or modify it (as long as you share it too).

    See thingiverse :
    And Github :
    and Youtube :

  • Great, Im looking for something like this for some time now.

    What would make it even better is an included SSR that can switch of the whole printer.

  • Don't hesitate. I use a relay with real contacts…
    After the main power switch there is a small PSU that feeds the safety processor. The safety processor is in control of the mains power for the rest of the printer.

  • Interesting. Im looking on the schematic on thingiverse but im not getting how the relay is integrated in the circuit.

  • Hey guys.

    As another option worthy of a mention in a safety orientated topic, is the XYGAX Smart Switch;

    This auction has ended, but it will explain the features quickly until I have a page setup on my web site.
    With temperature probes available for build chamber, hot end monitoring and bed temps, with a gas sensor as well, added safety is assured.
    The seperate MosFET control for the bed is handy, the Duet is very capable I know, but it's good to have it.


  • Very interesting.

    Why a mosfet as the main power input and not an SSR?

  • @sungod3k:

    Very interesting.

    Why a mosfet as the main power input and not an SSR?

    Hey Buddy.

    Thank you. Yes it is a great little product. This unit was spawned from another product the designer makes for me.

    I posed the question regarding the MosFET compared to SSR to the designer and this is what he replied with;

    "Mosfet is DC SSR is used for AC. So if you have a 110/220V bed and run it from line voltage, the SSR is the correct option and if low voltage then Mosfet is the best option."

    Here is the instruction sheet if you would like to take a look;


  • Ah I see, I didn't think of the fact that your unit is for controlling a setup where the bed and the rest are powered from one PSU.

    In my case my bed is powered from mains, so my safety processor would need to sit before the bed and the printer plug.


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