them up was simply a matter of plugging them into the Pico
ITX. Check out Figure 4 to see the completed head assembly.
Arms
Additional Parts Required:
• Six Hitec servos
• Two low profile axis
• Four pairs aluminum tubing connector hub
• Four aluminum tubing - 1. 50”
• Two aluminum L connector brackets (two pack)
• Aluminum multi-purpose servo bracket (rwo pack)
• Aluminum offset servo bracket with ball bearings (two pack)
• Black Plasti Dip
The arm redesign was probably one of the more drastic
physical changes I made to the J5 kit. The stock arms are
primarily built for aesthetics and expression rather than function.
They are not truly functional arms in that they are incapable
of picking up objects as they are not long enough to reach
the ground and lack the torque to manipulate objects of any
considerable mass. I wanted arms that were fully functional
and could – more importantly – pick up a foamy carbonated
beverage in a can. (Not to mention original Johnny 5 had long
spindly arms so the aesthetics of my design worked out nicely).
Here is the dilemma I faced: I needed the arms much
longer in order to reach the ground and pick up objects.
However, the basic physics of leverage show that the longer
the arm, the more torque it will need to manipulate things.
I also felt that adding an additional degree of movement to
the arm would provide a decent extension in itself, and give
the arm additional agility to manipulate objects. I chose to
separate the stock arm at the center and
add a true elbow joint, rather than the
wrist-elbow combination that the original
arm had. The arms still needed more
length, so I decided to mount the elbow
between two lengths of aluminum tubing,
which ended up adding about 5” in
length to the arms. Figure 5 shows the
upgraded arm detailing construction.
To address the additional strength
required for these upgraded arms, I chose
the strongest servos that I could find
compatible with the SES system: the Hitec
HSR-5990TG. At 7.4V, these servos output
417 oz-in of torque, which proved to
provide enough lift on the arms to not
only maneuver them, but also lift objects.
For budget reasons, I only added these
to the joints of the arm I felt would be
supporting the most weight: shoulder
rotate, shoulder lift, and elbow lift. Now
that the extensions, additional elbow, and
upgraded servos had been implemented
it was time to look at mounting the arms.
The stock configuration had the arms
hanging directly off of the shoulder rotate servo shaft, and
while that is sufficient for the stock arms, I felt with the
extra weight of the new upgraded arms it would not be
healthy for the servos over time. To alleviate the weight on
the servo shafts, I installed a pair of the low profile axis
units – another component of the servo erector set. These
units offset the servo and instead use a ball bearing axis
that is driven by the servo on a 1: 1 gear set. The arms
themselves mounted to the ball bearing axis which would
bear all the weight, leaving the servo shaft without any
stress and simply driving the rotation of the arms. The
LPA units were easily mounted to the chest using an L
connector bracket. Figure 6 shows a close-up of the LPA
mounting the arm to the shoulder of the robot.
Finally, I made a few changes to the grippers, removing
the middle finger to separate out two fingers from the
stock claw. Additionally, I painted on some Plasti Dip to the
inside of the fingers, providing a rubber grip to assist in
picking up objects. Figure 7 shows a side-by-side comparison
of the original stock arm and the new upgraded arms.
Conclusion
That about wraps it up for the modifications made to the
stock kit. Hopefully, it proved to be a solid exercise in what
you can do with the Servo Erector Set and a bit of imagination.
In upcoming articles, we will cover the details of adding an
onboard PC to your bot and what you can do with that much
processing power. I’ll also cover the vision, conversational
AI, and control software I am using on my Johnny 5 robot.
Figure 8 shows a comparison between the stock Johnny 5
and the modified version we have covered in this article. SV
Parts List
ITEM
• 10 LED stereo VU meter
• Three 4” Hot Bodies threaded shocks T-Maxx
• Traxxis steering block pair
• Six Hitec servos
• Hitec servo
• Black Plasti Dip
• Two low profile axis
• Four pairs aluminum tubing connector hub
• Four aluminum tubing - 1. 50”
• Three aluminum L connector brackets (two pack)
• Four 1-1/2” Nylon hex standoffs
• Eight 3/8” Nylon hex standoffs
• Aluminum multi-purpose servo bracket (two pack)
• Aluminum offset servo bracket with ball bearings
(two pack)
• Pan/tilt assembly
• Electronics carrier
• Interconnect bracket (extra from the J5 kit)
• Ten various rectangular LEDs
• Spool of 24 gauge stranded wire
• Two USB webcams
SUPPLIER/PART #
Canakit/ck106
Hobbytown USA/25010
Hobbytown USA/TRA3736
Trossen Robotics/HSR-5990TG
Trossen Robotics/HS-322
Home Depot
Lynxmotion/LPA-01
Lynxmotion/HUB-08
Lynxmotion/AT-01
Lynxmotion/ASB-06
Lynxmotion/NHS-04
Lynxmotion/NHS-01
Lynxmotion/ASB-04
Lynxmotion/ASB- 11
Lynxmotion/BPT-NS
Lynxmotion/EC-02
Lynxmotion/ASB- 18
Various electronics supplies
Various electronics supplies
Various electronics supplies
Canakit
Hobbytown USA
Trossen Robotics
Lynxmotion
www.canakit.net
www.hobbytown.com
www.trossenrobotics.com
www.lynxmotion.com
SERVO 09.2008 49
