It was bad luck that Ponderus, Fifth Imperial Lord of Varia, was born on a day with exceptionally light gravity. The Royal Minister of Standards duly weighed out the calibration stones, and a clockwork chain of events began: the Royal Metallurgist selected materials from her mineral store-room, and crafted the Standard Unit; from there, countless copies were cast at the Imperial Forge, endless couriers and emissaries spread out across the land, bringing the new metric to cities, towns, and villages alike.

Merchants groaned at the new metric, for, as luck would have it, the Fourth Imperial Lord had been born on a day of extremely high gravity, thus the old metrics had been small and easily carried. Now with Ponderus, the Fifth Imperial Lord, this convenience was gone. If someone purchased a simple quarter King of flour, it required seven large stones on the balance.

It was a mere four months later when Simon Waggoner, a potato farmer, had had enough. Over the course of the morning, he’d had to weigh out a thirty-king of potatoes twelve times, and something inside him snapped. In the middle of the market, he threw down his metrics onto the floor, shattering two of them. The entire throng of merchants, farmers, restauranteurs, household shoppers, and all fell silent and drew back. Inevitably, the word would get out, and soon armored legions of the Royal Knights would march in.

“Friends,” implored Simon. “I am nothing if not a loyal subject of his Supreme Majesty. But, if he loved his subjects, would he not give us a convenient weight, regardless of the day’s gravity?”

And thus the War of The Metric began…

“The superficial aspects of any popular art can be dislocated from the gut of it, marketed, and trivialized. That is the inevitable American artistic dilemma.” — Janet Coleman, The Compass

“Whether they knew it or not, the interest that drew them here was purely psychological – the expectation of some essential disclosure as to the strength, the power, the horror, of human emotions. Naturally nothing of the kind could be disclosed. The examination of the only man able and willing to face it was beating futilely round the well-known fact, and the play of questions upon it was as instructive as the tapping with a hammer on an iron box, were the object to find out what’s inside. However, an official inquiry could not be any other thing. Its object was not the fundamental why, but the superficial how, of this affair.”
— Joseph Conrad, Lord Jim

“Nobody thinks clearly, no matter what they pretend. Thinking’s a dizzy business, a matter of catching as many of those foggy glimpses as you can and fitting them together the best you can. That’s why people hang on so tight to their beliefs and opinions: because, compared to the haphazard way in which they’re arrived at, even the goofiest opinion seems wonderfully clear, sane, and self-evident. And if you let it get away from you, then you’ve got to dive back into that foggy muddle to wrangle yourself out another to take its place.” — Dashiell Hammett, The Dain Curse

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.