items such as lamp fixture parts (ends), legs (spring
doorstops), and ears (copper cups).
The wooden base is 3-1/2 x 7 inches, and was made to
fit into the lamp base near the bottom. The door stops are
screwed into the bottom wood, and the copper cups had
holes drilled to fit the lamp fixture. There is a 2 x 5 inch
platform mounted about two inches above the base on
which the two eye servos are mounted (see Figure 5).
In my first design, I had a third servo mounted to the
base with a rod to control the platform tilting to swivel
both eyes forward and backward. The tilting moved the
platform and eyes outside the exit hole range and also the
mechanics jammed, so I had to abandon this idea.
The Stamp carrier board is mounted on the lower right
side (see Figure 6). The microcontroller board is plugged in
vertically; you can see board numbers by the side of the
board. All of the electronic components are mounted on
the Stamp carrier board. There is just one IC (LM339), a
couple of potentiometers, resistors, and three LEDs. The
regulator ICs and capacitors are mounted on two different
small boards in the front left and back.
To add a little extra pizzaz, I mounted a flashing
rainbow LED to the front of Eye-Ears. I have found that by
inserting a clear glass marble in front of the rainbow LED it
appears to magnify the effects of the display several fold,
thus improving the color presentation.
All of the electronics are hard-wired to the Stamp
carrier printed circuit board (PCB). Do not install the
microcontroller onto the carrier board until after your
soldering is done on the Stamp board. Install the 16-pin IC
socket first, then the two potentiometers, and finally the
output resistors and LEDs. I used a nine volt battery
connector to run the power supply directly into the carrier
board. Be sure polarity is correct.
Standard 2 mm pitch headers are used to connect
directly to each servo. The six volt power supply will need
to be wired directly to the headers for servo power. Many
servos have different connections as far as which input is
the power (+ and -) and servo signal. You may have to
experiment somewhat to wire the header correctly. (On my
small servo — Cirrus CS- 20 BB — the red wire is +; the
brown wire is -; and the orange wire is the PWM signal
from the microcontroller.
Be sure to tie the grounds from the five volt regulator
and the six volt and nine volts together, so there is a
common ground. The Max Sonar requires five volts
regulated, and needs three wires for +/- power and a signal
Before turning on power, check for shorts by measuring
with an ohmmeter between pins 1 and 2 of the Stamp, and
pins 3 and 12 of the IC socket. Before you plug in the ICs,
connect power and check for proper voltage at the IC
sockets (five volts), the servo header sockets (six volts), and
+ 9 volts on the carrier board.
Turning It On and
Checking Out Operation
I would suggest checking operation in two parts: sonar
and IC; then the microcontroller.
(Note: Use proper grounding procedures to eliminate
electro-static component destruction.)
Check Sonar and
The sonar output and comparator operation should be
checked out before the microcontroller is installed. Insert IC
U1 (LM339) into the socket. Stand clear from the front of
the Max sonar units as they go through a short calibration
cycle after turn-on.
Adjust the threshold voltage at the LM339 for about
SERVO 11.2013 71