December 2007 Archives

I start with a tiny light dependent resistor and an amber 3mm LED (use a yellow LED if possible). These two are going to be good friends.

I pushed the LED and photoresistor flush together, then place the kissing components down on a bit of electrical tape.
Thus begins a very long staring contest.

Now roll the tape around a couple of times. Bend the component leads apart and press the tape together in between in order to keep light out.

I then take a thin strip of black tape and wrap it between the leads horizontally.

Squeeze around on the tape a bit in order to seal any openings. (Remember the round leads go to the resistor, the square-ish ones to the LED) You can check to see if there are leaks by hooking the resistor leads to a multimeter - in a dark room shine a flashlight on both ends of your new vactrol. If the flashlight changes the resistance reading on your meter then you have a leak and need to seal the package a bit more.

This is definitely a quick fix, (a sturdier vactrol should be constructed using epoxy or perhaps silicone adhesive) but I've found these to be a great way to control resistance. Just add a little LED flasher circuit and you're good to go for all sorts of effect pedal, synth, and general electronics mods and designs.

PS - Here's an LED flasher circuit:
blog.makezine.com/archive/2006/10/blinking_eyes_c.html

I've been working on a guitar effects pedal based around the rare and coveted Ampeg Scrambler. I used almost all the original components specified in the schematic and integrated a simple polarity protection for the DC jack. The biggest enhancement I've added is a sort of vibrato effect as an optional modifier to the texture control. I find the effect quite interesting, but I have a hunch there's a simpler way to achieve it. Currently, I have a timer circuit driving a makeshift vactrol (LED taped to photoresitor). The main circuit's texture control is then fed through the vactrol's variable resistance. I'm concerned that driving the vactrol's LED and 555 timer in addition to the rest of the pedal will create an impractical strain on battery life. Hmm, I should probably measure the circuit's current consumption to learn more. More to come.

Here's a shot of the first decorative accessory I made. Inspired by the Cybermen from the Doctor Who series, these are pretty simple and cute.

get it? Kind of like pronouncing "earrings" with a southern drawl? No? Whatev.Here's a completed pair of the etched copper earrings I've been making. You can't quite see it here but there's a thick layer of hardened clear coat protecting the face. They became quite durable after a brief curing process. I should have a few pair up for sale @ Etsy soon.

While looking for substitution tables I ran into this pic of the first transistor. Amazing, It could easily pass a work of art in a modern gallery. I find the zig-zagging lead particularly interesting (I'm assuming it's the base junction). I was assumming the shapes purpose was to increase capacitance, but it turns out the odd shape acted as a spring to suspend the large plastic triangle very gently over a germanium crystal.

It consisted of a plastic triangle lightly suspended above a germanium crystal which itself was sitting on a metal plate attached to a voltage source. A strip of gold was wrapped around the point of the triangle with a tiny gap cut into the gold at the precise point it came in contact with the germanium crystal. The germanium acted as a semiconductor so that a small electric current entering on one side of the gold strip came out the other side as a proportionately amplified current.

Damn, that's cool.

further reading:
http://www.pbs.org/transistor/science/events/pointctrans.html
http://en.wikipedia.org/wiki/Transistor

Here are some shots of the etching process I use to make earrings. Unfortunately I was in such a hurry bringing them to La Superette that I neglected to photograph the final product. No biggie, another batch is on its way for Etsy.
I've been having some issues with bubble in the "window" transparency sheets I've been using to expose the boards. I think I'll try straight up transparency sheets for the next round as adhesion doesn't really seem necessary to the process.
The bandsaw my studiomate, John, recently purchased has been a huge help in cutting these boards. It's hard to imagine I was previously used a dremel cut-off wheel. The bandsaw kicks up a lot less noxious dust and works much faster.