Make Electronics

Switching Basics and More 43

Experiment 6: Very Simple Switching

Ceramic capacitors, assorted. Make sure you get at least one rated at

0.0047 μF (which can also be written as 47 nF). See Figure 2-15.

Resistors
If you bought only a minimal selection for experiments 1 through 5, now’s
the time to buy a larger assortment, so that you won’t be stuck needing
the one value that you don’t have. 1/4-watt minimum.

Loudspeaker

Any 8Ω, 1-inch miniature loudspeaker such as part 273-092 from RadioShack.

See Figure 2-16.

Experiment 6: Very Simple Switching

You will need:

• AA batteries. Quantity: 4.


• Battery carrier for 4 AA batteries. Quantity: 1.


• LED. Quantity: 1.


• Toggle switches, SPDT. Quantity: 2. See Figure 2-12.


• 220Ω or similar value resistor, 1/4-watt minimum. Quantity: 1.


• Alligator clips. Quantity: 8.


• Wire or patch cords. See Figure 2-10, shown previously.


• Wire cutters and wire strippers if you don’t use patch cords. See Figure 2-4,
  shown previously.

In Experiment 3, you illuminated an LED by attaching a battery, and switched
it off by removing the battery. For greater convenience our circuits should
have proper switches to control power, and while I’m dealing with the general
topic of switches, I’m going to explore all the varieties, using a circuit to sug-
gest some possibilities.

Assemble the parts as shown in Figures 2-17 and 2-18. The long lead on the
LED must connect with the resistor, because that is the more positive side of
the circuit.

You’ll notice that you have to include a couple lengths of wire. I suggest green
wire to remind you that these sections are not connected directly to positive
or to negative power. But you can use any color you like. You can also substi-
tute patch cords, if you have them. However, learning to strip insulation from
pieces of wire is a necessary skill, so let’s deal with that now.

Figure 2-15. Ceramic capacitors mostly

look like this, although many of them are

round or bead-shaped instead of square.

The packaging shape is unimportant to us.

Figure 2-16. This miniature loudspeaker,

just over 1 inch in diameter, is useful for

verifying audio output direct from transis-

tor circuits.