Duet3D Ethernet - Sensitivity to static discharges



  • Hi, friends!
    I'm using Duet 2 Ethernet (main board v.1.04, ethernet board v.1.05) for about one year. It connects directly to the secondary LAN of my PC with short cable, static IP for both PC and board. Board is fixed to the plexiglass cover of my printer, not shielded, not grounded. Power supply is original Meanwell 24V 480W - it's grounded with printer's chassis and well connected with mains earth.
    Web control interface very often falls with "Connection Lost". Reloading page brings me to the connection timeout. Also I can't ping it (unreachable), LAN's LEDs - orange is always on, green is blinking when pinging it. Looks, like Wiznet chip is alive.
    Several months ago, because of this problem, I've soldered Ethernet board to main with IDC connector pins, but problems stayed. Fall of web control doesn't affect printing process - printer continues to print, but the only way to bring interface back is to reset main board.
    What I've noticed is that problem happens when I do something close to the printer. I don't touch it but static discharges may be a problem - now air is drier and looks like the problem appears more often.
    Maybe solution is to ground main board, but there is no ground connector and connect minus to ground may be not the best idea. Your thoughts, please.



  • @AfanasevSA advice when building the RepRapPro Ormerid was to tie the negative to the mains protective earth. Not neutral. I've been meaning to make a board that creates a bit of isolation for the dc negative from the mains earth but not had the time. Someone on here gave a circuit diagram that maybe suitable for that. Until I have sorted that I ground dc negative, the stepper motors, and cable shielding.



  • Buy a mains socket tester and make sure you mains protective earth is ok. After doing that run your machine through a plug in RCD breaker and I think most faults that would leave the earth dangerous trip the breaker.



  • @DocTrucker, I've decided to make some tests before connecting power supply minus with mains earth and chassis.

    1. When web interface has fallen, I've restarted it with M552 S0 => M552 S1 (by USB-console), and it went back. Did SPI had restarted with this sequence and W5500 nRST had triggered? I think that electrostatic discharge affects nRST because trace to the SAM4 is very long, and it uses an internal uC pull-up resistor. This is not always good for EMC, IMHO. Thinking about placing 10k resistor from nRST to +3.3V with a small cap to the GND.
      What if web interface will fall during print process and I'll send M552 S0 => M552 S1? Will it restart web immediately?
    2. There is C_GND through-hole, that is connected with GND using parallel RC. Thought about to connect C_GND with chassis.


  • Fixing static problems on printers, CNC, pick and place, etc, etc: Home run your grounds.

    Get a bolt. Size and shape will become obvious as you read this: Put it in a location such that you can run a wire from every negative power connector, and every metal frame member, to that bolt. Do "home run" or "star" each of these wires (do not multi-connect a given wire). Crimp (not solder) a ring terminal on every one. Stack the rings on that bolt and tighten.

    Try it and see if it is stable.

    If so, done.

    If not, run one more wire (ring terminal, etc) to the bolt, and connect that wire as directly as possible to protective earth ground.

    Every single time I've done this to someone's machine, it cleared up all glitchiness, etc, etc.

    Also, if your machine has belts, spray (lightly) them with almost any spray lubricant (that won't attack the belt rubber). If you are going to buy something, silicone based sprays work well... generally you can use almost anything that doesn't evaporate or attack.



  • @Danal, thanks for your answer, it's almost full. Interesting about belts. The same technique for boards - use star topology, don't route wide loops for single ended signals (ground is a return path for single ended signals), be careful with long high impedance lines and so on. This is EMC and it's cool.
    I want not only to eliminate the problem, but to find the reason, the most EMC-sensitive line.
    So, my first question from previous post is still actual. I'll try some solutions and post the result here. Maybe my 5 cents will be useful for colleagues, maybe not, but the result is interesting.



  • There is a ground tab right next to the 8P8C socket which might help out to connect to GND.

    If the wiznet chip is still alive but it's not talking to the main controller it could be the spi comms getting jacked up.

    If you have a PanelDue or usb and a laptop you could try to reset the network using M552 S0 followed by M552 S1 to see if a reset will bring it back up .



  • Hi everyone!
    18kOhm pull-up resistor from W5500 nRST to Vdd and 10nF pull-down capacitor to GND - all the day without problems.


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