Echolocators

A few years ago I was at a pub, celebrating a peers birthday, when a friend in education asked about using electronics to teach children sound--specifically how bats echolocate.  I was stunned, and probably turned alcohol into enthusiasm all night long.

Well, the joke was on me, because then I really had to build them.  The actual wiring and programming of the devices are pretty much textbook.  I was already familiar with the Basic Stamp and Ping sensor.  So the hard part was really making something novel, attractive and durable for children; it also had to meet the teacher's criteria.  A lot of this came down to the casing, and small tweaks in programming.

So a couple of prototypes were made.  One version was very ghostbusters, with a column of LED's that went from green, to yellow to red (corresponding to distance over 12 feet), all housed in a shiny handheld aluminum casing.  In the long run this wouldn't work; the proto box wasn't meant for something "real."  After that i tried some off the shelf items from tap plastics, but nothing fit the durability and pricepoint which had been spec'd.  Finally, i found a bunch of acrylic q-tip containers with lids at the container store, and began to modify them under the drill press.  One, or two of these boxes, may have died by my hands.

When the first unit was ready, there were two forms of output: 1) the 7 segmented display indicating the distance (up to 7 feet)  2) the audio, which was an analog of the digital output from the ping sensor.    

However, the teachers thought the theremin quality of the device was confusing, so instead it simply beeps in correspondence to the major scale, getting higher as the distance approaches 0, in steps of 1 foot.  If you're wondering why it only reads to 7' on the display when a prototype went to 12', it's because i didn't pay attention to the stamp's max output current per pin rating.  We'll leave it at that.   

Anyhow, the first one was made, by hand, all wire-wrapped, with zero documentation.  This would prove to be a fatal lesson as I would eventually need to make a total of 8 devices.  However, it's pretty cool that san francisco school children have been jacking bat-ear headphones into these, closing their eyes, and navigating a custom syllabus for over 2 years.