This circuit is build around a single IC that is LM380 with few more components like Mic, transistor, resistor and capacitor. LM380 is a general purpose audio amplifier, its gain is internally set to 34 dB. Operating range of LM380 varies from 10V to 22V. It comes in standard dual inline package. Working of this circuit is very simple. Provide power supply when you want to use classroom Mic. Now adjust the condenser Mic properly near to your mouth. So when you speak in front of Mic this signals are pre amplified with the help of transistor T1 and this signal are now fed to IC1 that is LM380 pin number 6.
Relay control using mic and sound amplifier
During late night we often face problems from disturbances created by stray animals, unknown people and other moving objects which are quite [[wysiwyg_imageupload::]]annoying. At times such unwanted disturbances can even scare you in night. This circuit based project presented here can protect you from such unwanted movements of people and animals. This relay control circuit detects the presence of animals and human beings and alerts them by raising a false alarm in form of light.Whenever any unwanted sound is produced, it gets detected by the sound sensor. The weak signals are amplified by the amplifying unit, which in turn signal the relay to switch on and glow the bulb to scare the intruder. The transistor T3 is used in the switch mode configuration to turn on the relay whenever some sound is detected.