Elenco Upgrade Kit SC300 to SC750 - Manual (Page 34)

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Project #388
OBJECTIVE: To build a night-sensitive police car sound.
As the photoresistor (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. If the light in the room is not bright, the IC may turn on.
Wave your hands over the photoresistor. 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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