Avionics pin call out question

[Charles in SC]

I am currently putting my radio stack together and wonder if there is a cross reference/thesaurus somewhere on line that explains what some of the pin callouts mean. For instance ground is sometimes called LO, -14v, power ground, negative, common, etc. This one I can figure out but some are not this easy such as Com 2 speaker load ground.
Any help will be good.
Thanks in advance!

[RVDan]

A hard DC ground, which would be one to the airframe, threfore battery ground is called a ground. A signal lo is not always a DC ground to the airframe/battery. A signal lo such as you describe for a speaker may be isolated from the DC ground. One has to verify by the equipment data to determine if a siganl lo is in fact a ground or an isolated lo signal. Something like a data line lo can be either a DC ground or an isolated lo. So once again you have to know what the equipment requires.

Hope that helps

[Charles in SC]

Exactly the reason I want to find a way to define all this stuff!

[RVDan]

The key is that you recognize that lo's are not always DC grounds. You will need the equipment manufacturers manuals which will tell you what they are. If the manual shows a wire from say, the speaker going back to a pin on their unit, and not otherwise tied to ground, you can pretty much assume that you can't just locally ground the wire.

One good example can be found in another thread here discussing the insulating washers for mic and phones jacks. Most audio systems want the audio and mic lo's isolated from DC ground, and if mounted in a metal (conductive) part will provide a DC ground.

Again, it really depends on what the equipment manufacturer designed their system to do.

For things like lights, motors (mostly) and other things where the ground is for power return, than the ground will be to airframe. Lots of other discussions in the forum on DC grounding techniques to avoid audio and other noise on the grounds.

[Bill.Peyton]

It sounds like you need a friend to come by and help you get started. Check with your local EAA chapter. As a side note, most of the installation manuals give you a definition of each of the types of grounds. The Garmin manuals actually show you how to wire each connector and to prepare each wire for the connector. Download the manual for your device and study the installation instructions. In the back of most manuals are examples of how to hook up various avionics boxes to each other.

[Charles in SC]

Thank for the replies. My question was not about grounds, I was just using that as an example. My question was about if there was a thesaurus type of thing for this. My install manuals do not have the definitions that I need and after going through my radio install with several of my local EAA friends they had enough different opinions to make me uneasy about installing my radio harness without enough research to be sure I know what I am doing for sure in my own mind.

[SteinAir]

There isn't a cheat sheet that I'm aware of which spells that stuff out exactly, though 'lectric Bob's "Aeroelectric Connection" book does a pretty good job spelling out the basic. Also, it's a HUGE help if you get the entire thing drawn out (in something like CAD, Visio, Excel, etc..) before you start running wires - either do it yourself or hire it done (it's not that terribly expensive and can be cheap insurance). Once you have a big drawing for the entire avionics interconnection, it's much less painful and confusing to put it all together.

Cheers,
Stein

[Charles in SC]

Thanks Stein