Sunday, November 22, 2009

Harnessing the power

I've been wondering if I'm up to electrical work on the airplane since way back in 2006, when I attended the SportAir electrical wiring workshop at Oshkosh (and then retook it in 2007). Since then, I've installed the Vertical Power system and got a few electrical components going, but the radio harness? That's pro material, right there.

But today I finished -- sort of -- the radio harness for the Icom A210 radio and the PS Engineering 1000II intercom. I still have to select a spot and install the headphone and microphone jacks for the pilot and passenger. And I still have to run push-to-talk wires to the stick grips on the control yoke for both pilot and passenger. And I have to read up more to figure out exactly HOW to wire the push-to-talk wires at the microphone jack. But other than that, I'm done!

I also have to figure out how to wire up a small switch, which allows you to hear the last transmission you received. The PS Engineering instructions SEEM to suggest this is a separate jack, but I'm sure I'm wrong. It would be stupid to take your headphones out of one jack, and plug them into another. Oh, and I have to wire up the music input. Sure, it's all mono, but floating along listening to the Ipod (which would mute if I get a transmission) is a nice idea.

My next step is to take out all the pins that I've inserted into the ICOM A210 end of the harness, so I can slip some "snakeskin" on there. I don't like having all these wires hanging out.

Will it work? I certainly hope so. I did test the auxiliary mic and headset on Friday. I got carrier on the scanner in the hangar, but I didn't hear any voice. But, then again, the wires were all over the place and no doubt grounding everywhere.

I've learned a lot about audio in the last few weeks thanks to the help of fellow RV builders like Kevin Faris and Ted Chang, but I could stand to spend some more time learning how electrons travel over this whole harness.

I'm taking this week off from work, so it might be a good time to select a location for the headsets, and get everything wired in.

But even then I won't be able to test much other than the intercom. I haven't purchased a communications antenna yet (any suggestions?) or bought the coax cable I'll need.

But things are getting there. If -- and I think it's a big if -- it works and there's no noise in the system when I flip on the strobes, I tend to think the worst part of my fairly-spartan panel and its wiring, will be behind me. I bought the autopilot harness and the transponder harness already made. I just have to get a cable of some sort to power the portable Garmin 296 GPS and then I think we can move on to getting the engine work started and completed.

Updated: I started the process of removing pins from the Molex connector for the ICOM A210. Here's what the pins look like. See the little barb on the top? That's what holds it in place in the connector when you push it in.

So, theoretically, I should be able to insert a small wire (like this DSub pin extractor from Vertical Power (I've never been able to get the pins out of the Vertical Power power connection!) which would force the barb down and allow me to remove the pin from the backside.

No dice. I've tried all morning. I did learn one thing, though. See that loose black wire below? ICOM has this schematic which tells you to jam two #18 wires into a single connector. This is a bad idea and I knew -- after the fact -- this was a bad idea because Stein Bruch said it was a bad idea. He suggested just a single wire from both of those pins and then, to serve as a jumper, solder one to the other "upstream."

So I knew -- because Stein said so -- that this connection would fail and one of the reasons I'm pulling all the pins is to change that set-up. As you can see, it did fail. It failed on the first tug while trying to remove the pin.


  1. Congrats Bob! I know how I will ask when I get to that step. It is great that winter has held off so that you can keep working on it in the hangar!

  2. Mono? Are you sure? My PS Engineering unit pumps stereo music into my headsets...