The credit for developing this system goes to my
good friend and fellow project collaborator, Brian Lincoln.
I would like to take this opportunity to thank him for all
the hard work that went into developing this. His
willingness to share his creation with us so that we all
can benefit is truly appreciated!
Parallax Activity Boards Make
It Happen
Brian has put together a combination of components
that allow us to control not only servos, but linear
actuators, electronic eyes, and pneumatic cylinders as
well. Our desire to see how far we could push the
envelope on this system brought a few issues that needed
to be addressed. Every time we expand our plans, he
figures out how to make it work. His innovative solutions to
the problems that invariably crop up have allowed us to
expand our designs into several new areas. In order to
better understand how our system is put together, we are
going to break down the layout of our new witch’s scene.
This project is our most complicated design to date, and
includes all of the key components we are currently using.
At the heart of the system is the PAB which records the
puppeteered commands and stores them for playback. The
most important features for our purposes here are that this
board includes an eight-core Propeller microcontroller, 64
KB EEPROM, a mini SD card holder, and an onboard
breadboard which allows rapid prototyping.
For the witch and skeleton project, we incorporated
four separate PABs. With 21 different mechanisms being
used, we could have gotten by using only three boards
since each is capable of controlling eight components. By
using four boards, we were able to split out the
programming and wiring into a logical design. We had a
board for each major element in the scene, which were the
witch’s body, witch’s head, skeleton body, and skeleton
head. By assigning each segment its own board, it gives up
plenty of extra channels to expand the show in the future. I
wonder what we will dream up and add next!
This show incorporates not only the servos which the
board is designed to control but five linear actuators, two
pneumatic cylinders, and one set of electronic eyes which
need to be turned on and off during the performance (see
Resources). These elements required some additional
circuitry in order for them to be integrated into our system.
Of course, the real magic that makes everything work is
the programming Brian has developed. There are two
programs that are required, but all the work has been
completed already. If you are interested in giving it a try
yourself, you can download them from my website at
http://tinyurl.com/zqx3tfx.
Controlling Linear Actuators
RC linear actuators provide a tremendous amount of
torque for their size and have helped solve a multitude of
design obstacles. I have found many uses for them, but
they do come with their own baggage. They are designed
to be controlled by a PWM signal level of 5V. However, the
PAB inserts a 3.3K series resistor for protection. This
modifies the signal enough so that the linear actuator does
not operate. Therefore, a two-transistor booster was
inserted to create a 5V PWM signal which corrected the
problem. In the original design, we planned to use six
actuators to control the wrists, arms, and legs. The heads
would be controlled entirely by servos. As construction
commenced, we needed to re-think this design because the
plan did not survive contact with reality.
The witch’s head proved to be too heavy for the nod
servo to handle. I had great success with Jarvis (see the
September 2016 issue of SERVO) when I replaced his nod
servo with a linear actuator, so I went with that scheme
again (see Figure 1). This was the first actuator we had
incorporated into the puppeteering system, and it soon
became apparent that we had a problem. A little research
Post comments on this section and find any associated files and/or downloads at
www.servomagazine.com/index.php/magazine/article/December2016_Animatronics_Puppeteering-Characters.
DIY Animatronics
SERVO 12.2016 17
Figure 1. A linear
actuator is just what
the doctor ordered.
RESOURCES
VSA — http://tinyurl.com/hyvqtg3
MonkeyBasic — http://tinyurl.com/hzt5uxo
ServoCity — http://tinyurl.com/j3b3dgq
Parallax Activity Board — http://tinyurl.com/zev2eaa
Hitec Servos — http://tinyurl.com/hsennuc
Actuonix Linear Servos — http://tinyurl.com/zhuwqea
Adafruit Electronic Eyes — http://tinyurl.com/p4twuqn
Vixen Software — http://tinyurl.com/jafrky7
Renard Plus — http://tinyurl.com/jtlf4te
All Electronics — http://tinyurl.com/zazkwst
My You Tube Channel — http://tinyurl.com/nma2doj
My Website — www.halstaff.com
DIY Animatronics Forum — http://tinyurl.com/qjeehjs
