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Thread: Can someone explain RS232 and RS485

  1. #1
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    Default Can someone explain RS232 and RS485

    What is the difference between RS232 and RS485 and when do I need it? Also can I use my REN64 to run my Grinch? I know I won't be able to dim but if I can do that I can save a port on my PC.

  2. #2
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    Talking Re: Can someone explain RS232 and RS485

    Quote Originally Posted by mkess View Post
    What is the difference between RS232 and RS485 and when do I need it?
    There's a lot in the wiki, but briefly:

    RS-232 is an unbalanced signaling scheme that uses a change in voltage polarity to signal a change in state. It comes in various "flavors" -- RS-232B allows a change from -25 volts to positive 25 volts. RS-232C is most the common -- allowing the two states to be in the ranges of negative 5-15 volts and positive 5-15 volts. This voltage change is sent on 1 wire referenced to ground (TXD on your PC). The specified maximum run is 15 meters, although many push it a bit further.

    RS-485, on the other hand, is a balanced signaling method that uses differential changes in voltage to signal a change in state. It uses two wires and detects the difference in voltage between them. This differential voltage may be only a few thousandths of a volt (millivolts) to accurately signal a change in state. This is much more resistant to electrical noise, and results in the specified maximum run of 1000 meters (over half a mile). That's one reason the Renard controllers use RS-485 signaling. You don't need to worry how far the next controller is (unless you have a really big yard).

    Like I said, lots more in the wiki, or Google " RS-232/422/485 specifications".
    You'll find enough to put you to sleep for the next few years. Specification docs are dry reading... :???: :-)

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