Interior Lighting System, Part 3

Hours Worked = 3.25

Picking up where I left off yesterday, I worked on finishing the LCU. I cut a piece of masonite board to fit to the bottom of the project box to give me something to screw the circuit boards to. Next, cut the hole for the d-sub connector. Then I screwed the timer board and my relay board into the box, and crimped d-sub pins onto all the wires that run to the connector. I also wired in the timer board. And that finished up the LCU (I thought!)

Next, I had to build a harness out of the mess of wires that I had run long into the tailcone. Of course, when I labeled all these wires, I did so right in the last inch of the wire, and since I needed to strip the wires and crimp on pins, I had to move all 15 labels further down the wires. After that, I had to solder a spice into the wire that runs to ground, because I have ground running to two different pins in the connector.

I then cut all the wires to length, stripped them, and crimped on pins. Then the pins were installed into a connector.

Now, to actually test the system, I needed to temporarily wire up all the door switches. I can’t permanently install them yet, because I need the doors installed to properly locate where the switches need to be placed.

I hooked up a 12v power supply to the power leads that will come from the master switch to test all the dimmers. And it all worked! I had full dimming control of all the overhead lights, rear map lights, and foot well lights! I’ll have to wait till the panel is built to test the last dimmer. But that wasn’t the real test… this was the easy part.

The real test came next. I taped all of the door switches closed (as if all the doors were closed) and hooked the power supply up to the LCU. No lights came on, and no smoke escaped from the wires or the LCU. OK. Good so far. Then I tried opening one of the switches, to simulate opening a door. Aaaaaand…. NOTHING. Hmmm… That’s not right. What’s going on here? Back to the schematic. I checked that every wire on the diagram was highlighted to indicate that I had installed it… but wait! There is a little short line on the diagram that connects the door switches to ground, and I missed it! A nice easy fix. So I disconnected the power supply and installed the missing switch grounds.

Test #2: I powered up the LCU, opened a switch, aaaaand… just the one door light comes on, and I can hear the relays clicking in the LCU. OK, Still not right, but we’re making progress. Since the dimmers worked when hooked to the master switch power, I knew the lines between the relays and the lights were all good. Back to the schematic again. I started doing some basic troubleshooting, tracing how power would flow thru the circuit, looking at how each relay would energize, and I found it! I was missing a ground for the coils on the two lighting relays in the LCU! It wasn’t on even on the diagram. I must have missed it when I drew the diagram from my circuit prototyping software. Oops! Open up the LCU, solder on a jumper wire to an existing ground, and put it all back together.

Test #3: Powered up the LCU, open one of the door switches and BINGO! IT WORKS!!! Third time is a charm!!! It all works exactly like it should! I proceeded to test each switch to make sure it was all good, and sure enough, we’re golden!

That was a little stressful, but I’m really happy with how this is going to work!

Now if anyone sees in my tailcone, they’ll ask “What is that big red box? Something critical, right?” Yup. That makes my dome lights work!


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