Page 156 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

Diodes
Because the PIC is sensitive to electrical spikes (may cause a reset
or lock-up), we place diodes across the collector-emitter junction
of each transistor (Q1 to Q4). These diodes snub any electrical
spikes caused by switching the motor windings on and off.
The PICBASIC compiler program is as follows:
‘Fuzzy Logic Light Tracker Program
start:
low 0 ‘Pin 0 low
low 1 ‘Pin 1 low
pot 2,255,b0 ‘Read first CdS sensor
pot 3,255,b1 ‘Read second CdS sensor
if b0 b1 then start ‘If equal, do nothing
if b0 > b1 then greater ‘If greater, check how much greater
if b0 < b1 then lesser ‘If lesser, check how much lesser
greater: ‘Greater routine
b2 = b0 — b1 ‘Find the difference
if b2 > 10 then cw ‘Is it within range? If not, go to CW
goto start ‘In range, do again
lesser: ‘Lesser routine 135
b2 = b1 — b0 ‘Find the difference
if b2 > 10 then ccw ‘Is it within range? If not, go to CCW
goto start ‘Do again
cw: ‘Turn the sensor array CW
high 0 ‘Turn on H-bridge
pause 100 ‘Let it turn for a moment
goto start ‘Check again
ccw: ‘Turn the sensor array CCW
high 1 ‘Turn on H-bridge
pause 100 ‘Let it turn a moment
goto start ‘Check again
Operation
When running, the light tracker will follow a light source. If both
CdS cells are approximately evenly illuminated, the tracker does
nothing. To test the light tracker, cover one CdS sensor with your
finger. This should activate the gearbox motor and the shaft
should begin to rotate.
If the shaft rotates in the opposite direction of the light source,
reverse either the sensor input pins or the output pins to the H-
bridge, but not both.

Team LRN Intelligence