dozen little squiggling quartz motors
propelling a dime-sized crawler along a
desktop or even a wall. At the time, there
were two glaring items missing from the
technology mix: a lightweight battery and a
practical means of closing the loop. While
battery technology hasn’t evolved much in
the past year, there have been advances in
miniature sensor technology.
A notable advance is the Tracker
position sensor from the makers of the
Squiggle. I had a chance to evaluate the
rather expensive Developer’s kit, shown in
the accompanying photo. The complete kit
(including batteries) comes in a plastic box
the size of an Altoid tin. There’s a Squiggle
motor, controller electronics, and the new
Tracker sensor in the box. In the photo, I’m
pressing the ‘forward’ button, instructing
the motor to push its plunger to the right.
The Tracker is a chip-based magnetic
sensor that can easily sit within the confines
of a dime. The chip features digital
encoding to offload the computational
burden from the main processor. Resolution
is a respectable 0.5 um, thanks in part
to a linear array of eight Hall-effect sensors.
The Squiggle is surprisingly fast.
The catch – there’s always a catch –
is the bulk and mass of the peripheral
components. For example, the ribbon
cable connecting the sensor to the
microcontroller is half as wide as the chip.
If you examine the figure closely, you can
see the magnetic strip that contains
alternating North-South poles is about
1/5th the size of the sensor chip. The demo
kit also requires a couple AAA batteries
So, although my vision of an insect-like
crawler made of Squiggle motors will have
to wait another year or more for battery
technology to catch up, at least there’s a
closed loop solution for what’s advertised
as the world’s smallest motor.
Assuming DARPA’s research into Hybrid
Insect Micro-Electro-Mechanical Systems
(HI-MEMS) is on schedule, the ultimate in
miniature closed loop systems is likely to
include organic components, as well as
electronics. Insects toting cameras and
microphones for military surveillance won’t
be very effective without some means of
directing them toward a specific target.
Perhaps we’ll learn something from
these hybrid insects – after all, some
of the simplest forms of life employ
closed loop systems. SV
My puppy enjoyed your magazine almost as much as I do. We mean
no disrespect. We both love your mag. I read it to Zelda.
I read Bryan Bergeron’s
editorial on sensors. Excellent. I
would like to build an altimeter for
relative not absolute altitude. I was
thinking a differential pressure
sensor or barometer.
Any suggestions on: type of
sensor? Make and model that you
are aware of? How? Circuit or
technique perhaps? I can receive
the data in any form into my
custom PIC-Based controller for
calibration.Thanks a lot for your
time. I realize you are pretty busy.
Response: Thanks for the
note. Tell me more — why relative
BTW, all absolute altimeters
ARE relative. You have to correct
for atmospheric pressure
fluctuations from weather, so you
have to build in an adjustment
mechanism. So, I’m not sure what
I am developing an inclined
ramp climbing robot; the project
is in process. I need to feed data
into an I/O on my controller from
I need to — in the absence of
encoders or dpslam data (from
data) — provide altitude data,
accurate to approximately three
feet or better if possible.
I need to monitor altitude
from the start position at the
bottom of the ramp, not altitude
above sea level. Basically, "How
high have I travelled?"
Response: Got it. So, any type
of altimeter will do — relative or
absolute — as long as you mark
start and finish, and assuming
For the sensor, I think this
should do it: www.sparkfun.
php?products_id=8161 Note the
17-bit/9 cm resolution.
SERVO 11.2009 7