1977 Intel 8255 chip – As a fun proximity sensor
Much more info below –
Note, mistake in the vid, meant 5 1/4″ floppy drive.
Created in 2007, this circuit was recently found in a box and I thought it worthy to share.
The Intel 8255 chip was used in the original IBM PC and many other computers of the time period.
https://en.wikipedia.org/wiki/Intel_8255
This circuit developed by trial and error, after noticing that an LED behaved oddly when a coil of wire was connected to Pin 5 (RD – Read). The coil was only connected by 1 of its wires and thus acted more like an aerial. Onward from there, of finding extra pins that responded to different levels of static electricity.
Touching the coil to reset, presumably creates an overload condition on Pin 5.
Scrubbing the hand on a piece of wool type material sets up the charge.
This circuit went through several variations…the one shown responded great to people walking on the carpet past the experiments table, when we lived in Minnesota. With such large static electricity ‘pressures’ as carpet produces, the effective range of interaction for the circuit can be approx 8ft.