Josh:

Had a similar challenge just a short time ago and recommend you look at CAN=
..
It is a very robust, both electrically and as a protocol.  I used the
MCP2551 and the plus is that every node can be a master or slave which
solved a LOT of problems for me.  (I am using a compiler with a CAN routine
in its' library so I did not write the code in assembly language so I canno=
t
speak to the level of complexity in implementing CAN that way.)

http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=3Den010405

And the speed and number of nodes it can handle are superior  to others
mentioned.

Hope this helps,

Rich

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Josh Koffman
Sent: Wednesday, July 28, 2010 11:43 AM
To: Microcontroller discussion list - Public.
Subject: [EE] Transmitting a signal over 300 feet

Hi all. I need to transmit the output of an industrial photo sensor
over wire about 300-500 feet. The sensor will be outputting 0-10V
pulses at up to 100Hz. Everything needs to be UL approved, so I've
been looking at modules from B&B Electronics (http://www.bb-elec.com).

My initial thought was to use some TTL to RS485 converters to make the
signal balanced, then put it back into TTL at the other end. I'd have
to do a voltage divider for the 10V sensor.

Then I remembered current loops. Now I'm thinking that a current loop
transmitter/receiver pair would be a good combination. They come with
significant isolation and supposedly are quite good at dealing with
external interference.

Does this make sense or am I heading down the incorrect path?

Thanks,

Josh
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