The ideal driver is a RS422 driver. These are protected from ESD and can 
deliver a lot of
current from a long way. I have personally used them at 1000m. They are 
bidirectional so
will work well for the dual-led.

LEDs are current devices. As long as the cables are protected from 
transients, the scheme
will work reliably.

--Bob

Josh Koffman wrote:
> Hi all. I have a bit of a design challenge I'm grappling with. Here's
> the deal. I have a friend who wants to make some remote indicator
> lights. In the beginning they will be controlled by switches, but I
> will be building a PIC based system in the future.
>
> We've talked about how to deal with long cable runs in the past, but
> this application is slightly unique in that the indicators are
> bi-colour LEDs. These are the ones where they are two diodes wired
> back to back. At the moment I'd like to avoid having to put in a
> remote PIC mainly due to the tight delivery schedule he needs. So how
> best to provide protection when the polarity of the line will be
> changing? Let's guess that the line length will be between 50 and 400
> feet of cat5 cable.
>
> Also, I haven't done the calculations yet for voltage drop. If anyone
> has done this in the past, tips on good voltage to use (to deal with
> line drop) would be appreciated. In the future I will be moving to a
> more solid state design and I'm thinking about using an open collector
> or similar driver with a slightly higher voltage to drive the long
> line.
>
> Thanks!
>
> Josh
>   

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