you need and quickly put your prop together using only a
screwdriver, an Allen wrench, and a few common
What is this Going to Cost Me?
The cost will vary widely depending on which project
you are planning to undertake. If you will be hacking a toy
you already have, for example, the only cost may be for the
controller. However, if you need to purchase all the
components for one of the complete projects, the cost will
be in the $300 range.
Can You Hear Me?
The simplest way to get a talking character up and
running is to start with something where much of the work
has already been done. Finding an existing toy or prop and
adapting it to fit our needs will greatly reduce the time and
effort required to achieve our goal (Figure 1).
The primary problem with this approach always seems
to be that the supplied controller wasn't easily hacked and
doesn't allow us to replace the provided audio track with
one of our own. In addition, instead of using servos to
provide the movements, they utilized small DC motors.
A talented group of haunters from Haunt Forum
attacked this issue and came up with a board that lets us
control the motors as we wish. I took their design and
added an onboard stereo player to supply the audio tracks
and a PICAXE chip to handle the trigger duties. I now have
a single board solution for hacking these props.
Once you have selected your character, you will
proceed with a bit of simple surgery. The wires connecting
the jaw motor will need to be removed from the circuit
board and attached to the new controller.
If you're interested in following the progression of the
process, you can check
out the full thread at
The circuit works by
turning a MOSFET on and
off as it responds to the
tone track created in
Audacity. More info on
this process can be found
later in this article, as well
as in the Instructable on
the board put together by
Jeff Haas at
For this article, I originally planned to hack a broken
monkey toy and replace the provided circuitry with
something similar to the one referenced above (with my
modified version), but things did not go as planned. The
monkey used a single motor which was attached to a
complex gear setup to provide multiple movements (Figure
2). This meant that I would be unable to isolate the jaw by
simply hacking its separate motor. So, it was on to Plan B.
My other option was to replace the existing motor with
a servo and use a circuit like the one developed by Scary
Terry to drive the jaw. Again, I’ve tweaked his design a bit
SERVO 08.2015 37
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Figure 1. The poor monkey selected for surgery.
Figure 2. Wow! There’s a lot going on in there.