Building the Hardware
If I used this system in an actual haunted house
capacity, things will likely need to be set up much
differently. Each dropper assembly will need to be where it
can be positioned effectively. A suitable audio system
would need to be installed, etc. In this article, I will
describe how I built the basic demo unit and offer some
ideas for customizing and expanding it. Additional
resources for some of these options are at the article link.
The first thing to do is put together the prop dropping
assemblies which consist of one standard servo and one
continuous rotation servo. In Vern's original article, he hot-glued most of the parts together. I looked through my
parts bins and found many miscellaneous brackets, so I
decided to connect the servos in this manner for a couple
reasons. One, if a servo was damaged, replacement would
be easier. Also, I could handle heavier props without
worrying about the servos coming apart. Figure 3 shows
some of the servos with the various brackets needed to
The standard servos horns were connected
to the bracket that ties into the continuous
rotation servo. The standard servos then
mounted to my wood platform via some right-angle brackets. I chose to use wood spools
available at any craft store and screwed the
horn from the continuous rotation servo into
the spool (Figure 4). It's important to make sure
the horn is centered before drilling into the
spool, otherwise it will wobble when winding
up the prop. This might cause the prop to
bounce and not reset properly.
The hole in the spool allows you to screw
the servo horn into the continuous rotation
servo. With the brackets attached, that
completes the wind-up stage of the servos.
FIGURE 3. Building the servo frames from brackets.
FIGURE 5. Wind-up stage completed.
FIGURE 4. Attaching the servo horn to the
FIGURE 6B. Alternate angle.
FIGURE 6A. Completed dropper assemblies.
48 October 2014