CHAPTER 14 ■ VARIABLE RESISTORSIn this circuit, an LED (D2) has been connected to the third lead of the trimpot (R2). The maximum
value of the trimpot has been decreased to only 500 W.
When the trimpot dial is in the center, the resistance is split evenly between the two LEDs, 250 W
each. As the dial is turned left and right, the resistance is delivered unequally between the two LEDs. The
brightness of one LED increases and the brightness of the other LED decreases. It’s like the speaker balance
control on a car stereo.
Cadmium-Sulfide Photoresistors
Cadmium-sulfide photoresistors (see Figure 14-11) are extremely popular in robotics. They’re lightweight,
inexpensive, fascinating to look at, and mimic the visible-light responsiveness of the human eye.
Figure 14-10. Brightness balanced LEDs circuit built on a solderless breadboard