> I am planning to have 8 devices on an I2C interface, but with a
> cable length
> of atleast 50 meters (thats 150 feet). I was thinking of making use of a
> max483, but there must be a better way... I was also thinking of mixing
> power lines with signal lines, only having 2 wires to the I2C
> unit. Each I2C
> unit will just be a DS/LM75. I know that I2C was ment for short distance,
> but i was thinking that lower the clockrate to say 100hz would help. (or
> better yet a clockrate that is out of phase with AC power lines... I was
> also thinking about sending the data by using the AC power lines... Does
> anyone have a clue of what to do ?

        Well I am no expert, but I have done what you are proposing. I have a ru
n
of about 40 meters, 3 LM75 devices and 1 MAX I2C device that senses on or
off conditions (don't remember the part number). Anyways, I find that it
works OK, I do use a slower clock speed and usually read from devices more
than once (I have it set to 10 times) and then filter out the highest a
lowest value. It works almost flawlessly, I have all the devices hooked up
in a daisy chain fashion using 4 conductor phone cable, power, GND, SCL and
SDA. I found that you have to bypass the supply on each device (kind of
obvious, but I didn't do it at first). In my case I have a sensor outside,
in the fridge and in my upright freezer (gets down to -25 degrees C in
there) and each device works well. If you have any questions let me know.
TTYL