are not your “normal” 3 mm LEDs. Due to the
limited board space available on
Microcerebrum, standard LED and resistor
combinations were eliminated in favor of
Kingbright all-in-one LED + resistor packages.
That’s right; a current-limiting resistor is already
included inside the LED. These are Mouser part
numbers 604-WP710A10ID5V (red) and 604-
The final oddball item is/are the
photocell(s). I know this is going to sound
crazy, but I tested 30-40 different photocells
for enabling/disabling the CD4011 output
gate, and the only ones that worked were
surplus ones manufactured by Clairex and
available from BG Micro (e.g., CL905HL).
Yes, you can use other variable resistance
controls (e.g., trimmer pots), but if you want a
photosensitive robot vision ganglion, then you
need to use BG Micro part number RES1439.
While we’re looking at the Parts List, you
will also notice that 20 2.2M ohm resistors are
specified. You’re right, that circuit board can’t
hold 20 resistors! Rather, two extra long 22M
ohm resistors are fabricated from these
individual resistors. By soldering 10 2.2M ohm
resistors together serially, we are able to
concoct a 22M ohm resistor (see Figure 9).
A small strand of 30 gauge wire-wrap wire
is then soldered to one end of this long
resistor and run down to the other end. This
combination is then secured inside some heat
shrink tubing and soldered onto the board.
The final eccentric look of these long resistors
is used for imitating an insect’s antenna. If that
mimicry is too goofy for your taste, a standard
I included a mounting hole in Microcerebrum for
attaching it to an Actobotics ActoBitty robot (see the
July 2015 issue). This inclusion enabled me to raise
the board in Figure 10 above the aluminum chassis
of the robot, preventing short circuits.
Oh, and remember those headers for the
CD4011 outputs? This modular design feature also
allows you to selectively use only the sections of the
board that you need for enabling a programming-less
robot brain on smaller projects (see Figure 11).
Finally, I put my bug to work. By mounting a
44 SERVO 11.2015
Figure 7. Jumper wires are used for controlling
the behavior of Microcerebrum.
Figure 8. There are six sensory inputs and two movement outputs on
Microcerebrum — similar to a fused metameric ganglion on the ventral
nerve cord of a grasshopper.
Figure 9. Each 22M ohm resistor is fabricated from
10 serial 2.2M ohm resistors soldered together.