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Thread: DMX moving head lights

  1. #71
    Join Date
    Aug 2013
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    Default Re: DMX moving head lights

    Quote Originally Posted by jchuchla View Post
    DMX is a balanced transmission line. The + is the main signal. The - is the inverse of the main signal. Ground is ground. The idea is that any noise on the line can be eliminated by cancelling it out at the other end. If your device needs to see a proper balanced DMX signal, then that's what you need to send it.
    Some devices will work without it. If you have one of that type, then you'd just use + and Gnd, and skip the - signal.

    The different controller do it differently. Some only send single wire unbalanced DMX. That is, it doesn't give you a - signal. If this is your case, and your device needs a properly balanced signal, then you need a serial to RS485 converter board. You can find these on amazon and ebay.
    https://www.amazon.com/dp/B014QNI0BC...a-319901615408
    I don't know why I'm having trouble wrapping my head around this...

    I have an E682. It's my understanding from earlier posts that you can control DMX elements directly from that. I am struggling with how exactly the 3 wire DMX cable gets connected to, for me specifically, an E682. The output from the E682 is +, Date and Ground whereas the DMX cable is +, - and Ground. Which one of those 3 is the data line?

  2. #72
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    Default Re: DMX moving head lights

    Oh, that's where you're confused. Let's expand the labeling on the connectors. That should clear it up.

    682
    Voltage +
    Clock
    Data
    Ground (power and signal ground)

    DMX
    Data + (the main data signal)
    Data - (inverse of Data +)
    Ground (signal ground)

    There is no power on a DMX line. V+ from a controller would never be connected to a DMX line.

    So before even consulting a manual. We can see we have two matching signals. 682 Ground matches DMX Ground. 682 Data matches DMX D+ So now the remaining question is if the 682 can do balanced DMX or not. I don't have one on hand, so I'll check the manual for the specifics. On the last two pages of the manual, there's a section called "2-wire balanced Outputs" Here's there's a pinout diagram. It shows that in this mode, the Clock (C) terminal is repurposed for DMX Data -. You also do need to install the jumper correctly on a per-output basis in the J22 jumper section.
    (having the jumper wrong won't break anything, but it won't work either)

  3. #73
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    Default Re: DMX moving head lights

    Perfectly explained... Thanks Jon!

    Now to have some fun planning for next year!

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