Figure 3. Hacking hobby servo mechanics.
Part two of this project involves how to make the
connection to your lens hardware. Initially, I would suggest
taking your servo apart, and using the internal electronics
to drive an external motor that was attached to a 5K pot
that would replace the servo’s internal pot and servo motor.
In Figure 3, I show just such a setup where I’m using a
large RadioShack panel mounted pot and a Solarbotics
( www.solarbotics.com) DC motor all hacked to the
controller board from inside a Hi Tec ( www.hitecrcd.com)
hobby servo. This will work, and it will allow you to find a
motor and gear that could match your lens hardware. If
your lens was harder to turn than any hobby servo that you
could afford, this is a good option to use. Good, but
difficult to implement.
An alternative would be to use the hobby servo “as-is”
and hack a drive system onto your lens that will match up
with the servo. The photo in Figure 3 gives a hint about
how to do this. Check out the website
www.servocity.com and look at their selection of chain
drive systems that can be mounted directly to your servo.
Servo City carries some very sophisticated mechanical
devices to attach to your hobby servo or hobby servo
controller that can handle a variety of functions. You might
find a selection of items that will handle that connection
without having to hack into anything.
Q. Kinda new to the field of electronics and robotics and such. Just curious if it is possible that there’s a servo out there that will push a button
momentarily to sound an alarm and then reset itself to
function again after a given time. Any specific
recommendations?
— Byrd, Manhattan, KS
A. Byrd, There is no such servo by itself that will do what you want. However, you can build a project that will. This question is somewhat related to the previous
question I answered above. You would like an alarm to
sound so you’ll want to add a buzzer to your
microcontroller design, or you could look for an “all in one”
solution. One such solution is the Orangutan SV-328 robot
14 SERVO 06.2010
controller which
you can find at
www.pololu.com.
This little board has
lots of useful
options on it like a
small LCD display, a
beeper, LEDs, and
I/O pins that can be
used to drive a
hobby servo. The
web pages on the
Pololu site for this
board include a link
to a library source
that users have
assembled to use the capabilities of the SV-328 (and other
Orangutan boards) to do various common projects,
including hobby servos and — of course — the buzzer on
the Orangutan board. At $65 US, it is a bit more expensive
than your standard Arduino board, but it has a lot more
functionality that will allow you to do all that you want to
do on a single board. Figure 4 shows a photo of an earlier
Orangutan board that I have and really like.
You can use any brand of hobby servo that you like or
may have on hand. To get your project to push a button,
use your favorite material to make a “finger” and glue it to
a servo horn. I like to use Lexan plastic and hot glue for my
jobs. If your project needs to be more robust, then drill
holes and use very small screws to permanently mount your
“finger” to the servo control horn.
Q. I have a Kondo KHR-1HV Humanoid robot kit. I built it and now want to program it. I have a website and a manual, but I want to take a class
or workshop to learn and pass my knowledge onto my
students. Any ideas? Classes or schools? It can be
anywhere. Hope you can help!
Figure 4. Pololu Orangutan
microcontroller.
— Jaime, Milwaukee,WI
A. Jaime, I have searched for more information on this robot but have come up blank. It appears that this model is no longer in production and getting help
from an English speaking user is going to be difficult.
I don’t like to give up though, so I’m putting out a call
to all of you helpful SERVO readers! If you know of an
active user group that can give after-market support to a
Kondo KHR-1HV owner, please send me an email. This is
your chance for 20 minutes of fame! I’ll put your
information into the next column I write. Any help that you
can give will no doubt be appreciated!
Well, that’s it for now. I have some good questions
queued up for next month dealing with sonar hacking and
the Arduino. Keep on building those robots and keep on
sending me those questions at roboto@servomagazine.com.
I’ll do my best to answer them! SV
