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Showing posts from January, 2013

Projects Past: The 2009 Automatic Cat Feeder

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In 2009 I took a week off from work to build an Automatic Cat Feeder to ration food to the overweight household cat. This was a project built from need and it had a deadline because my girlfriend and I were heading out of town for Thanksgiving.

The requirements were simple: It needed to be easy to refill and dispense the correct amount of food twice daily. Early on I had an idea for a large rotating drum to dispense the food, it needed to be easily removable for refilling and heavy enough that it could sit on a motorized wheel and cause enough friction to be turned.

Figuring out a latch mechanism that dropped the correct quantity of food after one rotation was the first tricky part. I didn't want any electronics on the drum so it had to be completely mechanical. In the end I hot glued a small box to the outside of the drum which filled during rotation, when it started moving back towards the top a tab would be hit to fling a door open and drop the food out. A magnet held the door…

Projects Past: The 2007 DIY Projector

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I've had many projects over the years, the most involved by far has got to be my DIY projector.  It is also my first serious project. By the end of it I had vastly improved my knowledge of optics, electronics, woodworking, and even a little thermal dynamics.

Research started sometime mid 2007, the now defunct lumenlab forums had a whole community of people building DIY projectors. There is a lot of theory to learn, optics to figure out, components to buy, and bringing all the pieces together is no simple task.  For such a complexe machine, at the core it has some very simple principles: A point light source radiates light into a fresnel lens, which straightens the light through the LCD screen, then another fresnel lens angles the light into a special lens which can focus the light on a screen. Here is an image from engadget which demonstrates the light path:


The major problem with these sorts of projectors is that they tended to be very large. 1080p monitors at the time tended to …