P1.5 A light-seeking control system, used to track the sun,

is shown in Figure P1.5. The output shaft, driven by the

motor through a worm reduction gear, has a bracket

attached on which are mounted two photocells.

Complete the closed-loop system so that the system

follows the light source./nMotor

S

Gears

€

Photocell

tubes

*

Light

source

FIGURE P1.5 A photocell is mounted in each tube. The light

reaching each cell is the same in both only when the light source is

exactly in the middle as shown.