Ok, so as some of you already know, PacKay Productions is building puppets for the Glove Theater’s production of Shrek: The Musical (and my lovely wife will be performing the part of Dragon). Part of Kay’s design for Dragon included eyes that light up, and Kay figured that she could accomplish this by putting a battery-operated LED closet light in each eye:
The problem, of course is that to turn those things on, you have to physically press the front on each of them. That’s going to be awkward if you want to light up the eyes while you’re performing with the puppet. “Hey,” I told Kay, “I can move the switch outside the case… heck, I can probably put it at the end of a long wire, so you can have the switches for both eyes next to each other. And I could move the batteries to the end of a long wire, too, so you don’t have to have all that weight up in the eyes.” Kay was skeptical, however, because she didn’t want me ruining the one pair of these lights that she had. So I found another pair for $5 on sale at a hardware store and I took them apart.
The build seemed simple enough: there was a switch soldered to a circuit board that had the LEDs soldered on, and there were two leads from the circuit board to the battery housing, one of which had a resistor. I could de-solder the switch and put it at the end of long wire, and I could do the same for the battery. Easy-peasy.
So I set to work. I grabbed about three feet from my spool of cat5 cable and split it open to reveal the four pairs of twisted wires. I de-soldered the connection to the battery and wired it back in with one of the wire pairs from the cable. I now was able to put the battery three feet away from the LEDs. I then de-soldered the switch from the circuit board and soldered in one end of another pair of wires. I then tried touching the bare ends of that wire together to close the circuit and make sure everything was working.
Nothing happened.
“Uh-oh,” I thought. “I’m not going to be able to do this by the seat of my pants.”
See, I’m a geek, but I don’t really grok electricity the way most geeks do. There are equations for things, and I mostly ignore them and just do things by the seat of my pants because, for the most part, I can get things to work that way. I don’t bother sitting down and crunching numbers because… well, that’s work. And I hate work. That’s why I mostly write computer code–coding isn’t work, it’s fun.
So, I started asking around for help. As luck would have it, one of my former coworkers Don came by the office this past week for a visit, and I chatted him up about it. He did some quick addition on my whiteboard, and he gave me one crucial piece of advice: buy a multimeter.
So, on Friday, I grabbed a $35 multimeter from RadioShack. On Saturday, I took apart the other LED light and started testing voltages. I tested at the two terminals on the battery pack. The multimeter read 4.77V. I tested where the two leads connected to the circuit board with the LEDs and switch. 4.75V. Ok, good, I’ve got numbers to compare with. I then tested the circuit I had soldered together at the battery pack. 4.75V. Ok, that’s good. Then I tested at the circuit board? -4.75V. … … wait. NEGATIVE 4.75V?
A little voice in my head said, “They don’t call them Light Emitting Diodes for nothing, Pack.”
So I de-soldered where I’d connected the wires to the circuit board and re-connected them with the proper polarity. VOILA! It worked!
Emboldened by my success (and spurred by the fact that my ham-handed soldering had damaged one of the switches so it was no longer a push-on, push-off switch but appeared to now only function as a momentary (push on, release off) switch), I trotted off to RadioShack and grabbed two larger switches and a little plastic project case to house them in.
Another hour in my in-laws basement, and I was done!
The switches are close enough together you can turn both lights on at the same time, but you can also choose to light up either light individually. Now all we have to do is mount these in Dragon’s eyes and figure out where the best place to place the switches.