11 Jul
2007
11 Jul
'07
9:58 a.m.
On Tuesday 10 July 2007 15:18, Tony Duell wrote:
And that 90V battery was probably the single biggest reason why I never built
one of those...
Popular Electronics did a cover story on one of those circuits one time, I
forget exactly when, but it was back in the sixties I think. The author
built a bunch of these circuits (8? 10?), wired it up, and potted the
whole thing with some clear compound. Later on there was a variant on it
published with some sort of cross-connections between stages that did some
kind of sequencing, I think. There's been some threads about blinky-light
circuits in general going on in my yahoo group, "roys-tech-chat", if
anybody's interested.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, ?a critter that can
be killed but can't be tamed. ?--Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin
Relaxation
oscillator?
The one I was thinking of -- the neon bulb blinker -- is this circuit
R
o----------/\/\/------------+--------------+
| ---
--- O
--- C Neon Bulb
| O (e.g. NE2)
| ---
o---------------------------+--------------+
The circuit depends on the fact that a neon requrires a higher voltage to
strike than appears avross it once it's struck. R is chosen so that a
glow discharge cannot be maintained in the neon with the current
available from the supply through R alone.
Waht happens is that C charges from the supply through R. When the
voltage across C reaches the striking voltage of the neon, the latter
strikes and discharges C until the votlage across the neon is less than
the maintaining voltage. At this point the neon goes out, C starts to
charge up again.
This was probably the first circuit I ever built, before I went to
school. I know it was before I'd learnt to solder, I built it using those
'chocolate block' terminal strips. I thin R was 1M, C was about 0.1uF.
The DC supply was a 90V dry battery.