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Project #388
OBJECTIVE: To build a night-sensitive police car sound.
As the photo resistor (RP) is exposed to light, its resistance is very
low, thereby connecting the gate of the SCR (Q3) to ground. This
prevents the SCR from conducting, connecting the alarm IC (U2) to
the batteries. The alarm IC remains off until the light is blocked,
triggering the SCR.
Wave your hands over the photo resistor. Block the light with your
hand and the speaker (SP) sounds.
Night Police Car
OBJECTIVE: To build a night-sensitive
machine gun sound.
Use the circuit from project 388. Connect the
jumper wire to points B & C for a machine gun
sound.
Night
Machine Gun
Project #389
OBJECTIVE: To build a night-sensitive fire
engine sound.
Night
Fire Engine
Project #390
OBJECTIVE: To build a night-sensitive
ambulance sound.
Night
Ambulance
Project #391
Use the circuit from project 388. Connect the
jumper wire to points A & B for a fire engine
sound.
Use the circuit from project 388. Connect the
jumper wire to points A & D for an ambulance
sound.
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