Night Police Car; Night Machine Gun; Night Fire Engine; Night Ambulance - Elenco Electronics Snap Circuits Instruction Manual

Project #388
Project #389
Night
Machine Gun
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.
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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.
Project #390
Night
Fire Engine
OBJECTIVE: To build a night-sensitive fire
engine sound.
Use the circuit from project 388. Connect the
jumper wire to points A & B for a fire engine
sound.

Night Police Car

Project #391
Night
Ambulance
OBJECTIVE: To build a night-sensitive
ambulance sound.
Use the circuit from project 388. Connect the
jumper wire to points A & D for an ambulance
sound.