September 8th, 2008


Making a PID controller out of an op-amp.

So you've probably seen this story about the table that keeps a ball in the center by using a touch-screen to sense where the ball is and tilt the table accordingly.

In the Reddit comments for the story, someone linked to the PID Controller page at Wikipedia, and wow has that thing gone uphill since the last time I looked at it.

The most interesting thing I learned by reading the (new version of) the page came from an off-site link to a PDF file about the control system for a little self-controlling helicopter project. It turns out (page 22) you can build a PID controller from an op-amp, two resistors, and two capacitors. You do have to do some math on the resistances and capacitances to calculate Kp, Ki and Kd. But even so, what a cool little trick!

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OpAmps - is there anything they can't do?

Making any surface into an interactive virtual whiteboard with the Wiimote.

You've probably seen Johnny Lee's TED Talk on using the Wiimote as a motion tracker, but did you know he's done a whole series of projects using it?

My favorite? The "turn any surface that can display an image (actively or passively) into an interactive whiteboard" project shown in the YouTube link above. The source for the whiteboard (and a couple more videos) are available for download from his web page at CMU.