Make Electronics

Experiment 11: A Modular Project

88 Chapter 2

R1

R2

R3

Q1

Q3

C1

D1

R4

R7

Q2

C2

L1

R8

R5

R6

6V

DC

Figure 2-107. By adding a 2N2222 general-purpose transistor, we amplify the signal
from Q2:

R8: 1K
Q3: 2N2222

Other components are the same as in the previous step in constructing this circuit.

100

K

15K

0K

K

u)

00u)

K

1K

0K

10

10

1

V

DC

Figure 2-108

Add the second 2N2222 as shown in Figure 2-109. In Figure 2-110, once again

the previously wired section is in gray.

If the accumulation of electrical components is beginning to seem confusing,

remember that each cluster of parts has a separate defined function. We can

draw a block diagram to illustrate this, as in Figure 2-112.

Using the second 2N2222, you should find that the output is more clearly

audible, at least within the limits of your tiny 1-inch loudspeaker. Cup your

hands around it to direct the sound, and you’ll find that the volume seems

to increase. You can also try using a 3-inch loudspeaker, which will create a

generally better audio output while still remaining within the limits of the little

2N2222 transistor. See Figure 2-106, shown previously, and Figure 2-111.