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Common Cathode or Common Anode?

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  • Common Cathode or Common Anode?

    Talking to an Atlas guy at Trainfest, the question looms. As you may know, Atlas purchased BLMA a while back. The BLMA signals have flown off the shelves, and are NLA. As you also might know, Atlas makes (generally unavailable) signals. However they are polarized exactly the opposite of their newly acquired BLMA company. The Atlas guy alluded that they were going to somehow meld these together. Maybe he meant "melt" them together. What is the consensus of the group? Which should prevail, Common Cathode or Common Anode?

    Not that this question will determine what happens.

    Jim
    Take the red pill

  • #2
    Just follow the world practice, and things will work out just fine.

    The reason common anode is more common is because its easier to sink current than to source it. With either common anode or common cathode you'll have one terminal connected directly to a supply for all LEDs and the other side having the dropper resistor and a control transistor per pin (or IC outputs that are transistors on the inside) either sinking or sourcing a current.


    Louis L&R Western Railroad
    Pacific Northwest Logging in the East Coast

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    • #3
      Unless you build your own, I personally like Zstuff for trains signals. Easy to wire and extremely reliable, adjustable triggering sensor, and they operate very well'..A little salty, but you know the old saying'. You get what you pay for:'...[:-smile_green]


      Ted

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      • #4
        This was more of a hypothetical question than the 'real' question. I favor the common anode connection for the reason Louis mentioned. Control circuit wise it is easier to take the cathode (- side) to ground than to raise the anode (+ side) to the firing threshold to emit the light.

        I probably should have asked "Is the Atlas/BLMA future switchover going to effect YOUR layout?"

        Jim
        Take the red pill

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        • #5
          No. I'd looked at BLMA and Atlas when I first started planning signaling, but BLMA didn't make signals that matched my prototype and it was hard to tell whether Atlas's devices would handle my track arrangements.
          James

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