Heat Or Light Activated Alarm Circuit
The circuit utilizes a 555 timer configured in astable mode to generate a square wave output that produces a tone. The activation mechanism relies on a heat or light sensor, which, when triggered, allows current to flow through Q1, a transistor that acts as a switch. This switching action enables Q2, also a TIP 3055 transistor, to amplify the audio signal generated by the 555 timer.
In this configuration, the 555 timer's output frequency can be adjusted by varying the resistor and capacitor values connected to it. The output from the 555 timer feeds into the base of Q2, which amplifies the signal significantly. The TIP 3055 is chosen for its ability to handle higher currents and voltages, making it suitable for driving a speaker directly.
The circuit may include additional components such as resistors for biasing the transistors, capacitors for filtering, and possibly a diode for protection against back EMF generated by the speaker. The speaker, connected to the collector of Q2, produces sound when the amplified signal drives it. This arrangement allows for a responsive audio output that reacts to environmental changes detected by the heat or light sensor. The tone generated by a 555 oscillator can be turned on (activated) by heat or light. That causes Ql to conduct transistor W2 (TIP 3055). Q2 (TIP 3055) acts as an audio amplifier and speaker driver.
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