Lights, camera, action

I worked on doing some tests of the lighting circuits. I am working on a bike for Burning Man and I'm going to use the same lighting technique, so I got a chance to try out what I want to do. I started with the red/blue 3mm LED's and the green 3mm LED's from I decided to wire them in opposing pairs so I wouldn't have to space them as close (I figure the glow from an LED travels about 1 foot down the polyethylene tubing, so I can get away with spacing them out every 2 feet if I make a pair that shine away from one another.) It really wasn't too bad at all … here's the photo essay:

Here's the LED's as they're shipped. The red/blue is on the top; the pin on the side that's flat on the lens is the red anode, the other side is the blue anode, and the middle is the common cathode. On the green, the flat indicates the cathode.

I cut the leads short on the LED so the resistors can be soldered close; this eliminates the need for using insulation because the leads can't be bent to short out anymore. Plus it's compact.

The red/blue LED's need two resistors; the red side gets a 180 ohm resistor and the blue gets 150 ohms.

The green only needs the one resistor.

Here's what the finished pair looks like. I'll have to remember that I want to address each cluster, not the whole thing, so I shouldn't solder the cathodes together.

A couple layers of tape diffuse the light so it blends better.

The next step was getting the ribbon cable inside the 3/8" inside-diameter tubing. Initially I tried just stuffing it in but it ended up being all floppy inside the tube. I bought some 1/4" outside-diameter tubing, taped the ribbon cable to it, and then stuffed it through. It works a lot better for two reasons: first, the ribbon cable lays flat, and second, the light assemblies are hard to push down the tube — I was using a piece of stiff wire, but with the additional small tubing, I can just guide it through without a push-rod.


Bought a new MP3 player

In the process of shopping around for more tubing stuff for the lights, I stopped at Goodwill Fashions (376 Jefferson Rd., in Jefferson Plaza) and found they had an MP3 player for $25 so I picked it up. It's a Memorex MMP8560 with 128MB RAM. With 4 times more RAM than the Digisette, I'll be able to put on more music stuff. However, the interface to get it to start is more complex so I'll probably need to use the computer chip to run it (whereas the old player needed one button to be pressed to start, the new one needs to be powered on first and then started with the play button.)

The good news is that it only draws 40 mA. If I use a linear regulator from 12 volts to get to 1.5 volts (it uses a single AAA alkaline, not a NiMH cell) I'll only have to get rid of around 450 mW of power as heat which was as good as I got with the buck converter anyway. (Remember that the rationale there was to pick a higher-than-audio frequency and the transistor tended to go linear. I might try the buck converter again anyway.)