I need a way to get a 2 way connection between a laptop and the arduino over 100'. USB does not extend far enough, so I'm not sure what I can do. Cheaper is better.
I'd put two RS485 transceivers at each end and use two pairs from a CAT5 cable to get full-duplex TTL Serial communication. I'm pretty sure RS485 is rated for 1000 feet. Put a USB to TTL Serial at the PC end and connect to pins 0 and 1 at the Arduino end.
RS485 is bi-directional but half-duplex (can only send one direction at a time). By using one pair for outgoing data and one pair for incoming data you don't have to worry about turning the line around. The driver chips are under $2 each. 100 feet of CAT5 cable can be had for under $10.
could you link me to some driver chips? I dont really know what to look for. So your proposing:
comp <> usb to serial <> driver <> cable <> driver <> 0/1 on arduino
could you link me to some driver chips?
That should get you started. Not all these will to full duplex though. Look for ones with both A/B and Y/Z outputs, or use two chips.
Looks like the Maxim MAX488E would be an excellent choice. They are full-duplex (separate receive and transmit drivers) so you only need one 8-pin DIP at each end. Digikey.com has them for $3.28 each. Search for MAX488CPA+-ND