The Prawn of Time
Thursday, July 26th, 2007Leather and Prawns and BBC micros, oh my !
Via Wired …
the decomposition of a prawn sandwich is used to measure time. Attendees at this eccentric tech conference are enthralled.
Facing a crowd of hungry listeners, inventor James Larsson boldly launched his demonstration without offering anyone a bite of the Marks & Spencer prawn sandwich in his hand.
His decision was wise given that the stale lunch food no longer qualified as edible. Instead, it served as an integral part of the time-telling device that Larsson unveiled
The idea that computers could count the hours by sensing natural decomposition motivated Larsson.
“I’ve always found that very appealing because everything does change with time — especially sandwiches — and if you can just unlock the secrets of how something changes over time you can derive time from it,” he said.
Larsson is not the first to imagine a decaying delicacy as a tool to measure minutes. The freelance electrical engineer got his inspiration from none other than The Hitchhiker’s Guide to the Galaxy by Douglas Adams, in which the Total Perspective Vortex produces an image of the universe using a piece of fairy cake.
The prawn sandwich clock relies upon a piece of retro hardware from 1982 known as the BBC Micro. This computer, promoted in Britain as a learning tool more than two decades ago, offers a mere 32 KB of RAM and 32 KB of ROM.
But the simplicity of its design makes it anything but stale.
“There are importantly four channels of analog-to-digital conversion which are great for hanging little sensors off,” said Larsson. With just enough memory to store a model of how sandwich elements deteriorate differently over time, the BBC Micro gets hooked up to the three basic ingredients of prawns, mayonnaise and bread. The computer lacks a clock and is wholly dependent on these food components for an accurate measure — plus or minus a few hours.
Larsson found that prawns have an equivalent capacitance of 1 microfarad, “but the interesting thing is that changes over time, that’s the basis of this.”
“Two days in, the bread is getting drier and drier and the mayonnaise is pretty stable,” he said. “But all prawns have this catastrophic event at two days and 11 hours past sell-by date.” As these crustaceans rapidly decay, the machine dial inches away from “fresh” toward “lethal.”
The computer compares the changing prawn capacitance it senses through the input devices against a tested model to see how much time has gone by since it was last set using the sandwich.
Though Larsson’s device reported problems with mayonnaise sensing, it eventually caught up to within less than an hour of atomic time.
From the International Herald Tribune …
outdated computer monitors serve needs we didn’t know we had, according to the affable inventor James Larsson. For example, he uses a castoff cathode ray tube to discern when a Marks & Spencer prawn sandwich has gone bad.
The prawns also tell what time it is although the clock function, Larsson admits, isn’t quite what it should be. He is giving a demonstration with a day-old sandwich, inserting into each component a sensor with the total reading displayed on two wall-size clocks, one ordinary, the other with a face marked Stale, Lethal and Fresh. The needle stops just between fresh and stale; the clock is four hours off.
“At the lethal stage the clock is much more accurate,” Larsson apologizes. He once used an optimally stale sandwich for a public demonstration. “It was quite pungent and someone was sick, but it did tell the time quite well.”
Larsson, whose day job is to design electronic engineering for the water sculptor William Pye, describes himself as a hardware hacker
Larsson, 40, works out of the basement kitchen of a house on Camden Hill built by his great grandfather, the Victorian painter Herbert Arnold Olivier, who was also the uncle of Sir Laurence. Disused hardware fills the former plate racks, the floor, every surface. “The miracle of five years ago is now worthless junk and I find it rather upsetting that something that someone somewhere in the world had been sweating over is deemed waste material,”
“It’s a wonderful relief not to be constrained by either marketability or manufacturing or intellectual property protection, which is ruinous, or dealing with venture capital, which is horrendous, and still have an outlet to the process of invention.”
His latest invention celebrated the 32nd birthday (the 30th passed unnoticed) of Pong, a kind of tennis that is considered the first affordable mainstream video game. His is what he calls an adult version of Pong, themed around leather fetishism and ideal for technology conferences.
He demonstrated his kinky Pong at the Yahoo gathering in London last month. It features touch-sensitive high leather boots which are caressed in order to make the bat go up and down. Players who lose a point are “punished” by a motorized whip.
His next project is safer, sort of, in that electricity isn’t involved. The fact that fire, unlike electricity, is intrinsically binary has somehow inspired him to invent a video game powered by nozzles spurting jets of flame.
“It isn’t exactly an indoors project,” Larsson admits.
UPDATE : Al saw James Larsson speak at at OSCON recently and described him as … “obviously clinically insane, but in a great way.”
