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Sound-Activated Relay Circuit: Build Your Responsive Project
Circuit diagram
Notes:
- This delicate sound-activated switch can be utilized alongside a dynamic microphone as detailed above, or alternatively, it can be employed with an electret (ECM) microphone. When utilizing an ECM microphone, R1 (indicated with a dotted line) must be incorporated. A suitable resistance value would range between 2.2k ohms and 10kohms.
- The two BC109C transistors constitute an audio amplifier, the amplification factor of which is modulated by the 10k potentiometer. The output signal is subsequently boosted by a BC182B transistor. To maintain stability, the amplifier is buffered with a 100uF capacitor and a 1k ohm resistor. The alternating current signal at the collector of the BC182B is converted to direct current by the two 1N4148 diodes and a 4.7uF capacitor. This direct current voltage will
- immediately activate the BC212B transistor and trigger the relay and LED.
- It’s important to acknowledge that this circuit does not exhibit “latching” behavior. The relay and LED function momentarily in response to audio surges.
More about components
Integrated circuits, commonly known as ICs, are complex electronic components that integrate numerous discrete components – such as transistors, resistors, and capacitors – onto a single semiconductor chip. These chips are manufactured using sophisticated fabrication processes, enabling them to perform a wide range of functions. In this circuit, the BC109C and BC182B transistors are examples of integrated circuits. These ICs offer advantages like reduced size, lower power consumption, and improved reliability compared to using discrete components. They are essential for achieving miniaturization and enhancing the overall performance of electronic circuits like this one.
More about components
The BC109C and BC182B are both NPN-type bipolar junction transistors (BJTs) which are integrated circuits. BJTs are current-controlled devices, meaning that a small current flowing into the base terminal controls a larger current flowing between the collector and emitter terminals. They are commonly used in amplifiers and switches. The BC109C transistor acts as the audio preamp while the BC182B further amplifies the audio signal. These ICs are fundamental building blocks in numerous electronic systems, delivering precise amplification and switching capabilities.