Data Sheet

49. Touch-controlled

Sound Effects

Build the circuit shown. Press the

switch (62) and you will hear the siren

from the speaker (93). Now touch the

touch plate (80) several times and you

will hear gun sounds. Hold the touch

plate (80) and you will hear machine

gun sounds.

Note that in this circuit your nger is a

good enough conductor to activate the

gun sounds with the touch plate (80)

even though your nger was not a good

enough conductor to activate the LED

(69) in project #30. This is because the

input T2 is a low impedance input, which

means that it has a very low opposition

to current ow. So for input T2, even

your nger is a good enough conductor

to allow enough current to ow from T2.

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50. Siren Sound Effects

Turn the switch (62) ON and you will hear the siren from the speaker (93). Press switch (61) and now you will hear the

Fire Engine Siren. Turn OFF the switch (62) and replace the press switch (61) with the touch plate (80).

Turn ON the switch (62) and you will hear the siren, but now when you touch the touch plate (80) it does not activate

the Fire Engine Siren. This is because T1 has a higher input impedance so your nger is not a good enough conductor to

allow current to ow to T1.

51. Magnet-controlled Alarm Siren

Replace the press switch (61) in the circuit above with the reed switch (83). Move the magnet (7) towards the reed

switch (83) and you will hear the Fire Engine Siren. This circuit simulates motion detection alarms that are in your house.

1st level

2nd level

Level block