Saturday, November 06, 2010

Dome Wiring Work

Free time has been scarce lately, but today I managed to squeeze in a few minutes to work on the dome wiring.

As with droid #1, I'm using PC fan connectors to connect the dome electronics. This way I can unplug them from the power bus bars with a minimum of fuss. Most of the electronics only use the positive and negative signals, but the third signal can be used on the front logics to trigger the display of a text message.

It's just a matter of cutting the cable in half, and soldering one end to the wires leading to the part to be powered, and the other end to the power source. I always need to remind myself to cut a segment of shrink tubing and string it on before I start soldering.

Each part had been tested in isolation, and I finally had a chance to test them all together.

The green LED for the rear PSI was not as bright as I wanted, so I replaced it with a 10 cd, 3.2Vf, 20mA LED, and replaced its 1Kohm resistor with a 300 ohm resistor. Nice and blindly bright.

Ah, but how to mount the small circuit board? Tom Doucet's PSI holders include a backing piece designed to work with Mike Velcheck's PSIs. The board layout for Mike's PSIs is somewhat different, so I needed to clip all but one of mounting points.

With one of the two mounting holes on the board threaded onto the one mounting point that I left intact, I drilled a 9/64" hole through the other mounting hole, and through the PSI holder backing plate.

I used a 1/2" #6 nylon screw and nut to secure the board using the hole I just drilled.

The dome electronics are mounted onto the dome ring. I'm using six D Cells in series to supply 9 volts to my dome electronics. Experience with droid #1 shows that I can run the dome lights for months at a time without having to replace the batteries, but they do make the dome somewhat heavy. I was considering using C cells instead, but my sub-minimal effort to find battery holders for them at Radio Shack turned up empty, so D cells it is.

I still need to cut some segments of wire to finish the connections to the bus bars. I also need to purchase and wire up a white LED for the front holoprojector, I keep forgetting about that.


alanrw said...

Victor, have you looked into RC LiPo batteries? They have a lot more longevity than Duracell and can be recharged. Pretty cost effective as well as lighter and smaller with much more M.A. capability.


Victor Franco said...


Until your post I had never heard of LiPo (I am familiar with Lithium Ion, though).

They look like impressive technology, although I would want a supply of 9 volts, and my very brief search using Google turned up multiples of 3.7 volts.

I will give this some consideration.


alalnrw said...

Victor, I bet Mike is familiar with them. You are correct, the cells come in 3.7V so you could go with a 2 cell pack (they charge up over 4.1 volts fully charged and then go thru an electrical regulator to get back to 9.0V. But check with Mike, he will know.