Make Electronics

Switching Basics and More 91

Experiment 11: A Modular Project

R1

R2

R3

R10

R6

Q1

Q3

Q4

C1

C3

R4

R9

R7

Q2 C2

L1

R8

R5

6V

DC

Figure 2-113. R10 connects the slow-running oscillator at the top of the breadboard to the
gate of Q2, the PUT in the middle of the breadboard. This modulates the audio oscillator,
with addition of a smoothing capacitor.

100

K

K

10K

15K

0K

K

u)

u)

00u)

K

1K

0K

1

1

10

10

V

DC

Figure 2-114. This schematic shows the

same circuit as in Figure 2-113:

R10: 10K

C3: 2.2 μF

Figure 2-115. This photograph shows the complete alarm-audio circuit on a breadboard.