10 Jul
2007
10 Jul
'07
8:01 a.m.
On Jul 9, 2007, at 6:54 PM, Cameron Kaiser wrote:
Relaxation oscillator?
Tony may feel very old, but I'm just feeling very dumb. ;)
It's an oscillator built around a capacitor and something with a
breakdown voltage, a neon lamp for example. The capacitor charges
slowly through a resistor at a calculable rate, and then (partially)
discharges through the neon lamp quickly when its ionization
threshold is reached and it conducts...then the cycle repeats. You
vary the frequency of oscillation by changing the value of the
charging resistor.
In this manner, you can have a blinking light with one resistor,
one capacitor, and (of course) a neon lamp. What's neat about it is
that the blinking light is actually an active part of the oscillator,
rather than just an indicator that displays the oscillator's state.
-Dave
--
Dave McGuire
Port Charlotte, FL
You're making me feel very old. When I was a kid,
I used to make a
neon
bulb blink using one resistor and one capacitor.
Relaxation oscillators are fun. I like the UJT version as well,
though UJTs are getting harder to find than they once were. I have
two or three 2N2646 UJTs left.