Maximum Distance Without Driver

[CocaColaKid]

Just curious what the maximum distance would be say running at 2400 baud using just the TTL included in the PIC itself through a 22 gauge wire. Looking to make runs of around maximum 250' and I have very limited space available on the PCB. If this is possible is there any way to protect the PIC from ESD without a driver?

[CocaColaKid]

Just to follow up, I'm trying to share data bi-directionally with another PIC that could be up to 250 ft away using just 3 wires. Two of those are used for power already though :O I have a circuit working right now but just not sure about reliability and ESD protection.

[dalescnc]

Im trying to do the same thing but only using 2 wires the 12volt supply and gnd Just hope i can get some results i would be interested to try your code with modulating it thats if you dont mind ?

Thanks
dale

[mackrackit]

This is not a direct answer but I doubt if you can get 250 feet out of it. The low level (5 volt) signal from the PIC or most serial ports these days are not powerful enough.

The best I have ever been able to do was around 85 feet using shielded cable in metal conduit.

To get more distance I went with a 422 using full voltage.

I built two converter boxes to add to the system. This was going from a PC to a PIC. PC to box 1 with short cable and PIC to box 2 with short cable. Ended up with about 300 feet between the two converter boxes.

[CocaColaKid]

Well after doing quite a bit of reading I believe I will not be able to accomplish what I want with what I have. I was browsing the archives of Nuts and Volts and came across the column by Scott Edwards entitled Nifty Networking Chip Link Stamps Far and Wide. It this article Scott shows you how to through together and RS485 network with very minimal parts. There are only 5 parts needed in this setup, a 120 ohm, 1K and 10K resistors, 0.1uF decoupling capacitor and the Linear Technology's LTC1487. This little device appears to fit the bill for exactly what I'm looking for. Suppose to be able transmit up to 2000 ft according to the spec sheet anyways. That is way further than I would ever need to go so this in theory should work fantastic. I will post my results when I get the parts in from DigiKey in the next couple of day.

[CocaColaKid]

Well I received the drivers yesterday and went to work installing them on the old breadboard. Everything seems to be working good but I can only achieve about 175 feet on cat 5 cable. I figured I should be able to get a run of at least 1000+ feet without any issues.