The LEDs pictured require at least 8 volts to light in series, but they're being driven by less than 3, through a boost converter. The converter is a TI TPS61161, and was surprisingly easy to solder despite its small size and the thermal pad underneath, even with no solder mask and no solder paste. Surface tension really helps here. I just tinned the board using an iron and reflowed using a hot air gun.

The violin project made #1 in Fantasy Magazine's Top 10 Steampunk Gadgets!

Fun with an SnO2 alcohol vapor sensor.

The prototype PCBs for the Hackerbot Labs LED Driver board came in! It's kind of hard to tell, but they're an inch square. Either this weekend or the next I'm gonna try bringing it up.

I was trying to make an animation of a bouncing ball to illustrate some frame rate conversion issues at work. I wasn't able to get ffmpeg to turn the sequence of PNGs into a movie:

ffmpeg -i ball-%03d.png ball.mp4

Depending on the version of ffmpeg, I got either a useless error message or a misleading one.

The answer is to look at the files themselves:

$ file ball-000.png
ball-000.png: PNG image data, 640 x 480, 16-bit/color RGBA, non-interlaced

ffmpeg can't deal with 16-bits/channel. Neither can mplayer. (At least in the versions I was using.)

Adding -depth 8 to the beginning of my ImageMagick convert command line fixed the problem.

Porkshanks commissioned me to design an LED color organ driver for a functional art-piece modification of an electric violin, for Maker Faire. She herself had been commissioned to convert an electric violin to a tubepunk aesthetic, and was looking for a lighting effect more sophisticated than a plain glow. I built one that drives brightness based on loudness and huge based on pitch.

Direct link in case flickr is being obnoxious

I'm working on a commission that calls for a 3-color LED to respond to audio input. With appropriate parameters, it produces a fairly convincing flame effect. Here it is inside an egg Naj made for entirely unrelated purposes.

This week was a research phase. I'm putting together parts for a spectrometer.

Ingredients:

• The Optics of Spectroscopy - A TUTORIAL By J.M. Lerner and A. Thevenon
• Inexpensive 102-element photodiode array with built-in ADC
• Inexpensive holographic diffraction grating film

I just need some mirrors and I'm mostly set. I'm going with what is mostly a Czerny-Turner monochromator design, with two differences. First, the grating is a transmission grating, not a reflection grating, so the bottom half "flips around". Second, I'm using an imaging sensor rather than a single exit slit, so it's not actually a monochromator.

And here's a bonus photo I took of some lightbulbs through a diffraction grating. Incandescent on top, CFL on the bottom: