Page 277 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

etc.) affect its direction. Hence I removed the steering. But this is
still a good research area for advancing the overall design.
Adding higher behavior module
As the robot stands, when a certain level of light is reached it be-
comes active. We can add a higher behavior mode, feeding, by
adding a few more components (two solar cells and steering diodes)
and another comparator circuit. The second comparator circuit will
deactivate the motor when the light illumination level becomes high
enough, allowing the solar cells to charge the AA batteries, which
will be changed to nickel-cadmium (NiCd) batteries.
Figure 12.9 illustrates the behavior. When the light level is low, the
robot is off, or we can say it is in a resting mode. As illumination in-
creases, it reaches a point where the motor turns on and the robot
enters its searching mode. When the light level increases signifi-
cantly beyond this point (searching mode), the second comparator
turns off power to the gearbox motor, allowing the two solar cells to
charge the AA NiCd batteries, which triggers the feeding mode.
If you plan to add this feeding behavior circuit, keep track of the
current drain to the comparator circuits. It must not exceed the cur-
256 rent supplied by the solar cells or obviously no charging to the NiCd
batteries will occur.

Parts list for the solar-ball robot

1
(1) 5 / 2" transparent plastic globe (see text earlier in this
chapter)
(1) Gearbox (see text earlier in this chapter)
1
(1) 6" length of / 2" solid plastic rod
1
5
(1) 3" length of / 8"-OD, / "-ID plastic tubing
2
1
(1) 1" length of / 2" half-round plastic rod

12.9 Layering higher behavior

Team LRN
Chapter twelve