Homebrew Vactrols

[The Old Crow]

  The most interesting "homebrew" vactrol I have heard of is the LDR
Disneyland/Disneyworld devised to simulate a flickering gaslamp in their
haunted mansion attraction.  They used these all over the sets--even to
this day.

  What they use is a cluster of NE2-type neon bulbs, each hooked to a
simple half-wave rectified line voltage source through series RC
circuits.  Similar to the method in which a flashtube is triggered, the
neon bulb straddles the capacitor of the RC circuit and when the cap
charges at the time rate set by R (C was the same for all the timing
chains) to a voltage sufficient to light the NE2, the cap quickly
discharges and the cycle starts again.  Using several different values for
R in each node, a nice effect is achieved.

  Seal this light source in a small cannister with a photoresistor, and
you have your vactrol.


Crow

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