Archive for January, 2011

Oddball Hotplate

Posted in electronics on January 22, 2011 by raphaelabrams

I made a special hotplate for soldering all the circuit boards for the Blueman project. It’s 22″ long and 1″ wide. I made it out of a single block of aluminum that I CNC milled to fit two 750 watt heaters and a thermocouple. There’s also a PIC that monitors the thermocouple and has a relay to turn the heaters on and off. The display shows target and current temperatures to within 1/4 degree Celcius. Having this to do my soldering kept me from losing my sanity. There’s 0ver 1000 solder joints on each wand!




Posted in foolishness, robotics on January 21, 2011 by raphaelabrams

Tiny Jacob’s Ladder

Posted in Danger Danger High Voltage, toys on January 21, 2011 by raphaelabrams

OK, not really. But it does make little sparks and I had to do something with the extra bug zapper I had.


Before the dissection. “Not a toy.”

Here’s what was inside, with the addition of my own battery pack and a couple of wires, all glues to a piece of wood. Now it’s a toy!



Rainbow Wand Pictures

Posted in LED, video system on January 19, 2011 by raphaelabrams

I made a batch of about 20 very fancy persistence-of-vision LED display devices for Blue Man Group over the summer. They use a strip of 96 Cree RGB PLCC LEDs in one row. Every group of eight is driven by a tlc5947 chip, which is a 24 channel 12 bit pwm driver. There is a PIC microcontroller running at 40 mips doing IO and communications with a command board and a 4MB flash to store images on-wand.

These things have amazing color. It’s really hard to even come close to showing it in a photo, so I went for a somewhat abstract long exposure technique. They’re so bright I had to take pictures through a piece of tinfoil with a pinhole in it. Essentially I made sunglasses for my camera!

In the bottom left picture you can clearly see a pinup girl (the same one from the top image). That’s just from one swipe. The rest in that image are a close up of a lotus flower, a rainbow, and a picture of a lamp.


Shocker Swords!

Posted in Danger Danger High Voltage, electronics, Homeland Security, toys on January 18, 2011 by raphaelabrams

Yes! 800 volts of pure stupid! And they paid me!!!

I used a circuit from an electric flyswatter with the addition of a bleeder resistor on the output. It’s a very simple boost converter with a transformer on it. There’s two primary windings, so the circuit gets feedback. It’s amazing what you can get in Chinatown for five dollars! The full length of the blade has metal foil tape on it, with a channel going down the middle for sparks. The tape is coupled very crudely to the circuit because at that voltage it just sparks anyway. Hit any soft part of a person and they get a nice painful zap! Probably not dangerous? Heh! Heh!

Following will be a load of interesting things not in chronological order.

Posted in electronics, Soft Circuits on January 18, 2011 by raphaelabrams

I have been doing all sorts of fun stuff, but being very lazy about documenting it. Here goes!

Let’s start with a Soft Circuits class that I taught with Catarina a little while ago. We were doing the “voodoo doll” design, where a circuit is activated by having a pin stabbed through it. First is a happy Alexis with what might be a monkey robot. It got stabbed.

There was also a really cute little pillow guy most remarkable for having two eyes.

And finally another cyclops, but this time a bunny!

The trick to getting this circuit to work is to use conductive spandex. Yes, it exists and has it (catalog #A321). It’s expensive, but a little goes along way. The idea is that normal conductive fabric will not heal from a puncture — its metal fibers stay bent. But somehow this stuff springs back, making a good contact with the needle. So to make a needle activated switch you only need two layers of this stuff with a bit of felt separating them.