Communicate with board 75 feet away?

Other Miscellaneous
1

So in short I want to control a board (GPS-RTK2 in this case) from my computer while it sits around 75 feet away. What’s the best way to do this?

Can I use a serial to USB board and run a 75’ length of cable out to it from the USB port in my computer?

Is it something I should use some cheap radios for (3DR for example? https://www.amazon.com/s?k=3dr+radio)?

I currently have a couple USB serial basic boards (https://www.sparkfun.com/products/15096 and https://www.sparkfun.com/products/14050) and a couple USB- FTDI boards (https://www.sparkfun.com/products/9873) at my disposal. Would any of these work? It seems like there’s a length limitation with FTDI and I know RS-232 runs into the same problem.

Thanks for any help!

2

So in short I want to control a board (GPS-RTK2 in this case) from my computer while it sits around 75 feet away. What’s the best way to do this?

Radio would be an option. You just need to find radios that have the range and data rate you require. If you’re just using wire, USB, TTL serial and RS-232 serial won’t go 75 feet reliably and RS-485 would be the way to go.

There’s probably an easier solution, but something like the picture below on each end of your link and two 75’ long sets of twisted pair wire plus an optional ground should work.

FDX-RS485.jpg
FDX-RS485.jpg686×571 98.2 KB

I’ve not tested this so I can’t say for sure if it does what you’re looking for, but it should put you on the right track.

3

For the twisted pair cable that TS-Chris is talking about, I would look into CAT-5 cable. The electrical characteristics of ethernet and rs485 are close enough. Just watch the pinout for the connectors as it is not obvious (pairs are pins 1+2, 3+6, 4+5, and 7+8). I’d use two pairs for the data, and a third pair for ground.

RS232 (real serial with +/-12v levels) should be able to go 75 feet with a reasonable baud rate (9600 or less) as well.

/mike

4

Thanks for both of your replies. I’m going to try a few things in the next week or so and will hopefully report back with a working setup.

5

I ended up getting these cheap USB extenders via cat 5e and it works perfectly at 100’.

https://www.amazon.com/Monoprice-Extend … B003L14ZTC