Mon, 17 Sep 2012

Cambot’s First Campaign

— SjG @ 10:30 pm

Cambot is a project based on the Teensy development board. Cambot creates an infra-red “trip beam” that triggers a pre-focused Nikon D90.

To create an IR beam and detector that work in direct sunlight, Cambot pulses the IR source every 10ms, and compares detected signal between the on and off states. If it’s greater than a threshold, it’s considered a valid signal. The sensor also has a vary small aperture which is additionally shielded with a filter to reduce the ambient IR. When powered on, Cambot goes into calibration mode, which lights up an LED when it detects a good signal. This is critical for lining up the IR sources and detector — once a good signal is sustained for 3 seconds, Cambot goes into “armed” mode. When armed, breaking the beam will turn off the IR source, half-press the camera’s shutter for 10ms so the camera can compute exposure, and then fires off a burst of pictures before re-arming itself.

While there’s nothing in Cambot that couldn’t have been implemented with, say, 555 timers, counters, and gates, having the ability to drive digital logic with C code makes things much more flexible. When trying to determine the proper threshold values for arming and triggering, the ability to output hex data over the USB connector to a host computer was invaluable.

Here’s Cambot’s first run, when the trip-beam was positioned over a tempting milkweed blossom in the back yard.

If there’s any interest, I’ll post a circuit diagram and source code.