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  1. #11
    Quote Originally Posted by Robin Hewitt View Post
    If you are using opto couplers then your signal is current not voltage dependant and you are effectively proof against electrical interference.

    If it isn't working you are barking up the wrong tree if you think screening and more volts is going to help.
    Guess I didn't pay too much attention to the cabling, screening etc. Fact is that I get faulty signals from endstops if I run them at 5V without opto. Now I changed that to 24V proximity sensors and an opto near the BOB to ground the input pin. Now that's working.

    So the stepper drivers 5V opto inputs Enable/Pulse/Direction. Those are wired single ended with common anode.
    Just figured to go all in and use Line drivers where I can, and make it as stable a possible.

    The MAX490 chip looks perfect, if I read the specs. right. Then it can drive an opto directly (20mA) ?

    Thanks again, Bo Andersen.

  2. How far from ESS to drivers? Unless it's more than a metre or so this sounds more like a ground loop issue than induced noise. Not convinced you're addressing the right problem.

  3. #13
    Quote Originally Posted by irving2008 View Post
    How far from ESS to drivers? Unless it's more than a metre or so this sounds more like a ground loop issue than induced noise. Not convinced you're addressing the right problem.
    Thank you for your reply.
    From the ESS to the BOB, i would say <75cm, and from the BOB to the driver <50cm

    So the ESS drives the Opto-LED on the BOB, which again drives the Opto-LED in the drivers. (This is coming from converting, from Par-Port, to the ESS)
    Not sure if I can skip the BOB, and use the ESS directly to the Driver Opto-LED. But for convenience I kept them......

    When you say "Ground-Loop" is that from the PE (Earth symbol) so all units PSU's, PC, VFD etc. to be grounded.
    All the 0V pins on all PSU's: PC-PSU, 5-12-24-48V to have a common 0V
    Right now all the PSU's are running without common 0V.

    Best Regards, Bo Andersen.

  4. It is very easy to forget that as soon as you add a metal enclosure you are not just wiring electrically, you are also wiring inductively.
    Do you remember the old trigger operated soldering irons? They had transformer with lots of turns on one side and about 2 or 3 turns on the other shorted out by a thermocouple. The thermocouple received hardly any volts but massive current causing it to reach solder melting temperatures in a second or two and then miraculously stop on account of the fact that it was a thermo couple :)
    Anyway the point is, you don't need a lot of turns to make a transformer, one will do. The easiest way to make a single turn transformer coil (earth loop) is to drill a hole in a piece of metal then put a wire through it. Pass an alternating current through that wire and current will start to flow around the rim of hole. Drill another hole nearby with another wire through it and you have a circuit. No nearby hole and it will merely start to warm up.
    If you want to put wires through a metal plate I would suggest you knock one ruddy great hole, fill it with a Tufnol sheet then drill holes through that.
    If you make sure that everything going in or out goes through the same hole it will all cancel out. Simples.

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