During the fair, the event coordinator for the California Academy of Sciences (a science museum in Golden Gate Park, San Francisco) came by. The theme of our section impressed him, and he asked us if we would be willing to be a part of a one-night event. The Academy of Sciences hosts “Nightlife” —
adults-only events every week — where you can chat with
scientists about their work, have a drink, and enjoy the
Academy without kids running around.
For Halloween, he wanted to do a “pop-up haunted
house” with a combination of real science exhibits that let
guests glove up and touch specimens, along with
Halloween displays. The event would have DJs, people
attending in costume, local professional actors in elaborate
costumes and makeup, a big stage show as the finale, etc.,
and he saw our mad scientist props as fitting into the
theme. He asked if we would like to be a part of it.
Of course, we said yes! We did it the first time in 2015;
it went well, and we were invited back. So, now there was
an opportunity to improve some of the effects. That just
happens to bring us to the subject of this article: Bob, the
What About Bob?
I’ve been trying out various setups to control a talking
skull for a few years. Most of them work well, but it turns
out the big pain in the neck is animating the jaw to sync
with the dialog. We change what the skull says every year,
and the software plays back six different MP3s in a random
order. This means that each year, I write new dialog, get it
recorded, convert it to a robot-sounding voice (more on
that later), and then hand-animate the motions of the jaw
to work with the soundtrack.
I’ve been looking for a way to make this process easier.
One day on hauntforum.com, a user named mikkojay
posted a video and code about his “Jawduino.” He had
hacked a cheap audio meter and used it with an Arduino to
control a talking skull’s jaw automatically — with no tedious
hand animation needed!
The audio meter uses the KA2284: a chip designed to
drive five LEDs for a VU or signal meter. Best part is an
assembled board is available on eBay for about $1 shipped!
The post about the Jawduino went up on August 14,
2016. The “Creatures of the NightLife” event would be held
October 27, 2016. Since the parts would be coming from
China, I ordered two of the little boards, so if one didn’t
work, there was a backup. If they didn’t get here in time,
well, I could use last year’s technology.
Not only was the clock ticking, but mikkojay’s original
code was brief. It only used the Arduino to respond to the
output of the audio meter and control the jaw. It didn’t
control audio playback, and it didn’t have any way of
handling a list of MP3s.
As it turned out, the boards did make it in plenty of
time. I added sound playback and set it up so it would cycle
through six different MP3s, without repeating one until
they were all played.
Everyone’s a Comic
With a prop like this, the main question is, how was it
going to be used? We knew we would have a line of
people at one end of Africa Hall, waiting to get into the
haunted house area. Bob’s job would be to talk to the
people waiting in line, cracking a few jokes in the process.
I had the lead actor of the theater group record six
different voice tracks, and processed them into a robot-sounding voice using a tutorial on the Web. Why the extra
effort to do a robot voice? It’s because the skull I have uses
a servo to move the jaw, and it’s hard to disguise the
Instead of Bob being a “haunted” skull, we made him a
cyborg. He started life as a kit from Cowlacious Designs, so
he already had red LED eyes. Along the way, the original
Cowlacious audio control board got damaged. Some
chrome duct tape applied to
his skull created the cyborg
effect (Figure 1).
Here’s the list of
materials we used to make
the Jawduino controller:
• Screw Shield. Not totally
necessary, but it makes
life much easier (analog
• KA2284 audio board
• Serial MP3 player. I use
the Catalex unit, but
there are lots of others
• Stereo mini phono plug to
• Servo extension cable
• Assorted jumper wires
Additionally, you will
• A talking skull, with the
jaw animated by a servo
(not a DC hobby motor).
• Amplifier and speaker
By Jeff Haas
SERVO 09.2017 45
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Figure 1. A PVC stand is
needed to hold the skull
due to its weight. One
rubber eyeball is removed
to show the LED in the back
of the socket.