View Full Version : Sharing RS-232 lines

03-08-2010, 11:17 PM
What is the best wire connection technique when sharing a serial line? Would it be okay for 2-3 devices to recv from a single tx line?

I'm considering terminal strips, but thought I would ask to see if there is a better way.


03-09-2010, 04:44 PM
I had been struggling with this myself. Today I stopped by the avionics shop that did a LOT of work on an A36 Bonanza that I owned about 10 years. They changed out the majority of the avionics in the airplane and I never had a minute's trouble with any of it. I asked them this very question. They said this is how to do it:

Install a connector pin on a 3" or 4" wire of correct size for the circuit. On the opposite end strip back an appropriate amount of insulation. Solder the branch wires to this stripped end. Cover the soldered connection with heat shrink. They said this 'pigtail' can be as long as 6" in most installations with no concern for the introduction of noise as long as there are not wires carrying high current near by, but shorter is always better, and 3" or 4" would always be good. You can daisy chain the shields on the branch wires, or individually connect the shields to ground. I also asked if both ends of the shields should be grounded, as you will find in the G430 installation manual for example. They said you can shield one end or the other end, or both ends, for DATA wires and be OK. But for audio cables shield one end only , and at the connector end. I do not know the maximum number of branches you can make for a data cable, but think you'd be OK with 3. I have made 2 branches in the past and had no problems.

03-10-2010, 09:33 AM
Interesting solution using pig tails. I was considering using small terminal strips, but these pigtails might be even less prone to any noise. I have a GNS530 and I don't recall that the RS-232 lines needed to be shielded, but I will double check.

Thanks for the idea!

04-01-2010, 01:17 PM
I have found it effective to use a solder-type DB-9 connector, creating an "RS232 bus" by soldering a short wire across the top row of female terminal stubs, and connecting the serial cable to this. The mating BD-9 connector will then accept the pins from each of the serial wires for distribution to the various units.
Kenneth Melvin
RV-9A, Hillsboro.