Monday, November 12, 2007

Finished Soldering Dome & Sound Circuit

Tonight I finished soldering up the dome and sound circuit. I used typically questionable judgement, and decided to solder the last wire in place while everything was still wired up to the droid. Of course, all power was off. I was just too lazy to disconnect everything to solder one wire, and everything went fine. No harm came to the droid.

A single black wire connects the 12 volt ground that feeds the CFSound III card to the ground on the ULN2803. The ULN2803 actually has two ground connections on pin 9; one is the 12 volt ground for the CFSound III just described, the other is the receiver ground. The receiver ground completes the circuit for the power pulse on pin 1. The 12 volt ground is used to sink the current and cause a sound to play on the CFSound III.

It works! Sounds now play, and the dome rotates (kind of... more on that below).

I laid down two pieces of electrical tape onto the top of the frame, and secured the circuit board with a pair of wood screws.

I used masking tape to secure the loose wire leading to the roller switch that detects when the dome is centered, so it won't snag on the bearing as it rotates.

I let the system run for a good 20 minutes, when I noticed that the dome stopped rotating. Close inspection showed that the dome servo sometimes does not turn quite far enough to trigger the snap switch for left turns, and this causes the software to lose track of reality, since the dome should have turned.

I spoke with Mike, and the plan is to increase the throw on the servo to ensure that it does indeed turn far enough to press the snap switch.

I still need to clean up some of the wiring in the droid, but things are looking and sounding pretty good!

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