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A question about serial communications...?

RS485 lines need biasing resistors at some point in the network. None of the devices I'm using seem to have this.

Is there a nice neat module that I can bolt onto a DIN rail that does this, or do I have to have fiddly resistors knocking about inside panels?

I've searched everywhere, and can find nothing that does this.

Help!

4 Answers

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  • 1 decade ago
    Favourite answer

    RS485 lines only need termination and biasing resistors for long lines, where the reflections can cause the receivers to detect spurious bits.

    Several years ago, I used a DIN-rail mounted termination & biasing resistor package from Schneider Electric in the control compartment of medium voltage switchgear. It was nothing more than a circuit board with DIN mounts, resistors, and a couple of Phoenix connectors for jumpering the resistors in or out. (Schneider Electric calls their version of RS-485 'J-Bus', so maybe a search on that term would turn up something.)

  • John
    Lv 5
    1 decade ago

    Im surprised the device you are using does not have a slot to add biasing resistors or a terminator.

    I did have a similar problem as yours, but did not have a DIN rail. I had Phoenix connectors, so I had one of the techs grab a few Phoenix connectors and stick a resistor in the correct slots.

    I suppose you could just make one and stick in your DIN rails and put some loctite so they do not come loose

  • Anonymous
    1 decade ago

    you could use an empty din rail box, or a junction box.

  • 1 decade ago

    why are you upside down?

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