Page 87 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

Vcc
R2
33K M
Tip
2 120
7
4
3
15K
R3 10K
R1
4.7K

5.7 Photoresistive light switch

Vcc Vcc

66

UJT 2646

5.8 Photoresistive neuron

CdS cell decreases. This increases the voltage drop on R1 and is
seen on pin 2. When the voltage on pin 2 is greater than the voltage
on pin 3, the motor turns on. The threshold is adjusted using R1, a
4.7K-ohm personal computer (PC)–mounted potentiometer. This
is the basic circuit that controls the solar ball project in Chap. 12.

Photoresistive neuron
Figure 5.8 shows a light neuron. As the intensity of light increases,
the pulse rate becomes faster. The light neuron can provide the

Team LRN
Chapter five