Accurate LED Timing Circuit for Measuring Camera Response

LED timer eagle to board
A friend wanted to measure the linearity of his CCD camera, and asked for my help. He needed to measure linearity to 0.1% and wanted to do so by exposing the CCD sensor to a constant light source for varying time intervals. To decrease the effect of dark current, the smallest time interval needed to be extremely short, shorter than the shutter of the camera could achieve. Instead he asked if I could design a circuit to accurately turn on and off an LED, allowing the CCD sensor to be exposed for a much shorter interval than the shutter is capable of.

To measure the camera response to 0.1%, a range of 1000:1 is needed. This requires at least a 10 bit counter (2^10 = 1024). A constant current source is required to drive the LED so that its luminosity is constant. With those specifications in mind, I came up with a design.

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iPod Speakers

ipod-speaker-with-screenI had a broken first generation iPod lying around and wanted to do something with it other than let it collect dust. Since iPods have become a staple of music, I decided I would turn it into a portable speaker.

As I thought about it more, I realized an iPod would make a perfect speaker. The headphone jack could be the audio input, the hold switch could be the power switch, and the scroll wheel is the perfect size and shape for a speaker.
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Rocket Camera

A few years ago I attempted to put a camera in a small rocket. I had always had the idea in the back of my head, but I never knew how to do it. As soon as I saw this Make Magazine article I knew I had to try.

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