Machine Vision

Several genera of spiders are social and I was interested in the mechanisms by which Mallos gregalis coordinate their behavior in the absence of a cast system such as that used by social insects.

Mallos gregalis build webs that may cover three-quarters of a tree. Up to 30,000 individuals of both sexes and all stadia occupy the communal web. They cooperate in nest construction, care of the young, and prey-capture.

 
The original machine vision system used a 1.8 MHz, 4K (yes, 4 K) Ram system based on the RCA 1802 microcontroller. This system, programmed in machine language, was responsible for providing the signals to drive the camera (raster, I/O, camera timing, setting exposure), programmed output of a video signal, keeping track of time, determining how many spiders had moved in a group, and storing the data in memory. Nonetheless, the system was capable of recording 24 hours of data under natural photoperiod at one frame per 10 seconds. This was operational in 1977.More info on the 1802 series of microcontrollers is here.

The imaging provided by the camera and 1802 system were crude by today's standards. The camera only had native support for binary imaging and only at a 32 X 32 image resolution (The same as a default Windows icon). Nonetheless, that still allowed a potential for recording 1024 different positions for the spiders. A transformation to a binary image is shown above.

The pin I/O for the 1802 is shown above, along with the particular pins that were programmed for camera control and data collection. The 1802 was intended as a microcontroller, not as a numerical processing computer (such as the Z80). Being a CMOS device, it ran at slower internal clock speeds than a comparable device, but it was relatively insensitive to radiation and low voltage. Inside the Viking, Voyager, and Galileo space probes, an 1802 is still humming away!

Currently, a higher-resolution computer-controlled camera is used to follow up to 10 individual spiders at a time, 24 hours a day, for a full week, under natural photoperiod at 0.1 frames per second. Information on this project can be found here.