Tuesday June 6th, 2006|
Started Avionics Wiring
Today I started working on my avionics wiring in earnest. I didn't have someone make my avionics harness since my avionics setup is pretty simple. The intercom comes with a factory-made harness (which is pretty good, BTW) so I thought I would start there by wiring it to the SL-40. No big deal here. Just run wires. It's almost a one-to-one relationship except for the audio and mic grounds which are separate on the SL-40 but the same on the 244E, so I had to splice them together. I'm still not sure how grounding my avionics to the chassis will work if I want to abide by the single point ground principles of Bob Knuckles. Need to read up on that for sure. The last thing I want is noise.
I spent a little while testing what functionality I could. Looking at the DRE diagrams I tested the push-to-talk functionality by shorting the appropriate wires. Worked exactly as expected. I also pulled out my headset and touched the wires to the plug and I could hear stereo audio. There's a little noise in there, but I think it's coming from the fact that I don't have the necessary resistors in line (they come pre-soldered to the headset jacks). I also tested the co-pilot jacks settings and cycled through the intercom capabilities and as expected I could turn the radio on and off. With the radio off, the PTT functionality does not work. I also turned the power off to the intercom to check for failsafe connection to the SL-40. Yep...it worked. I think that even though the DRE doesn't draw much power, I'm going to put it on the main (read: not endurance) bus. This will shut off the intercom in case I get an alternator and/or engine failure. The last thing I want to do in that scenario is talk to the co-pilot. It will also shut down immediately all music, etc. The power saved from shutting down the intercom is miniscule..I believe it's only .4 amps or so..but that's something I guess. If I ever decide I don't want the intercom on the main bus it's just a matter of moving a fast-on and fuse from one block to the other, a mere 5 inches away.