Thought some of you guys might enjoy the geek factor of this one...a circuit based on a vintage chip used in the original IBM PC.
https://en.wikipedia.org/wiki/Intel_8255On clearing out some boxes the other day, this circuit was found and tested, it still worked so here it is.
Back in 2007, I bought a load of old gambling/fruit machine boards on Ebay. On which were several socketed chips including Intel 8255's.
After looking at the datasheet (
http://download.intel.com/design/archives/periphrl/docs/23125604.pdf ), several connections were tried out.
The RD pin, Pin 5, was noted to change an LED's output when a coil of wire was connected like an aerial.
After that, other pins were found to change behaviour in various ways.
A lot of fun was had mixing things around and seeing what would happen.
The resulting circuit below is of one version, another very similar version is shown in the video.
The end result is a circuit based on a 37 year old chip, that senses static electricity.
When testing up in Minnesota where we used to live, my wife's daughter came back from school one day and walked past in the livingroom some 8ft away, the circuit LED's flashed with each step
Reset is by touching the coil and each LED responds to static 'pressures' in the environment. The internal circuitry forms a mini scale of sensitivity for the 3 connected LED's.
Just a fun 'thing' of a circuit, which may have uses within electrostatic experiments as a sniffer.
There is a mistake in the vid. I should have said the coil comes from a 5 1/4" floppy drive.
[youtube]X7kS_CSyhjI[/youtube]
Author
Topic: 1977 Intel 8255 - fun proximity circuit (Read 5223 times)
