ECN Forum Forums General Topics of the Trade General Discussion Area Puzzle

I don't know about that one.... the EE student's I know in the old dorm I was in may be completely oblivious! They have VERY little practical experience. They are mostly in it for the money, not a love of electronics. I played with neon bulbs all the time when I was a kid. I still want to know how they made blue ones! Mercury with a phosphor maybe?


The CSEs will have fits over this as well.

Most colored neons (blue, green, white) use a phosphor; the regular orange ones have a mixture of helium and neon, and the purple ones are argon. I too remember making relaxation-oscillator flashers and similar "idiot boxes" as a kid. I couldn't afford the 90V B-batteries so I directly doubled the AC line with no isolation transformer. How did we survive those days?

If you want to gets maximum yucks out of it, figure it out using two light dimmers instead of just switches. I think conventional dimmers should work, if applied properly. If not, try substituting sensitive gate SCRs and a pedestal and ramp circuit, for the diodes in series with the switches.
Joe

Here's a very quick outline of the 4-state signaling circuit that I described above: