SnackBot

1
SnackBot

• Creator Chris Shepherd
• 7/7/05

2
Sensors/Behaviors

• Regular
• Bump Obstacle Avoidance
• IR Obstacle Avoidance
• Photo Reflectors Line Following
• Special Sensor
• CDS Cell with LEDs Color Detection

3
Sensors

• Bump connected to I/O port
• Switch not closed 5V
• Switch closed 0V
• IR connected to ADC port
• No hard-coded threshold necessary
• Calibration routine

4
Sensors

• Hamamatsu Photo Reflectors
• Used as digital sensors
• Over black surface 5 V
• Over white surface 0 V
• Will detect intersections

5
Special Sensor

• Color Detector
• Uses three LEDs and a CDS cell

220
100
150
27 k
CDS
R
B
G
6
Color Detector Data
CDS cell resistance
Object Red LED Blue LED Green LED
None 130 k 240 k 300 k
Red 5.3 k 160 k 130 k
Blue 11 k 55 k 190 k
Green 10 k 130 k 80 k
Blue lt 100 k under blue light Green lt 100 k
under green light Red gt 100 k under blue and
green light AND lt 10 k under red light