sounds, I made a controller and housed it in a gutted metal
alarm system cabinet (Figure 12). The controller used four
DPDT relays, three timers, the guts from a USB keyboard,
and a momentary type dry contact RF wireless remote
control. The relays and timers are used to start, pause, and
then reset the prop, as well as control sound effects and
lights (Figure 13). The start relay is wired in a self-latching
configuration by having one set of contacts used to apply
power to its own coil. The other contacts of the start relay
apply power to the motor circuit and the crypt lighting, as
well as triggering the one-shot 555 timer circuit that causes
one close/open cycle of its output.
Once triggered by the wireless remote, this relay stays
energized until power to it is interrupted. This keeps the
torso moving forward until it is extended all the way and
activates a position sensor that cuts power to the latching
relay (thereby resetting it). This also triggers the “delay
timer” to keep the creature visible for a few seconds.
At the end of the delay, the timer activates the
“reversing relay” which starts the prop moving backwards.
Once the prop is all the way back to the reset position, a
second position sensor activates the “reset relay” that cuts
power to the latching relay which shuts off the prop motor
and the lights.
Sounds for the prop were created with a sound editor,
and a sound effects file was saved to the laptop. To play
the sound file, I used the built-in “media player” bundled
with the OS. Each time the spacebar is pressed, the sound
file plays one time and then stops. I used a 555 chip to
create a one-shot timer (Figure 14) to short the terminals of
the spacebar on the innards of the hacked USB keyboard
(Figure 15). The one-shot timer is activated by the latching
relay. This started the sound effects as soon as the prop
started moving, which had the added benefit of covering
the sound of the drill motor running.
Crafting a Crypt
The crypt itself was modeled after a local style I’d seen
on my way to work. The
structure is a wood frame
(Figure 16) sheathed in
3/4 inch Styrofoam sheets
with PVC bars instead of a
door. I spent time carving
the foam to make it
appear as if it were made
of stacked granite blocks.
This obsession of mine
also became my brothers,
as we worked at a feverish
pace to get the prop done
for Halloween that year.
Late one night with
just one day left before the
big night, we were doing a
92 September 2014
A repurposed burglar
alarm box holds all the
electronics for the prop.
The wiring strip,
FIGURE 15. The 555
timer connected to
the USB keyboard.
FIGURE 14. A simple
one-shot 555 timer circuit.