Sound Operated Switch

Consider a situation in a bank or any organization where a sudden invasion by the burglars has taken place. Now all the staff has been handcuffed by the robbers and the main locker room full of valuable resources is at the mercy of the robbers. So is there any way to prevent this theft?? Yes, there is, if any buzzer is connected which can start ringing, alarming the local police or a camera fitted along with a GSM modem that can send the video to the police stations. But still the problem lies in the way to switching on these devices.

Consider another situation, when a person is at his room (in a hostel or a hotel) and a thief tries to enter the room at night when the room is dark and the owner is fast asleep. There needs to be a system for automatic switching on of the light and ringing of the buzzer alarm.

In both these situations, the solution lies in devising a way for automatic operation of a switch and to achieve this, one of the most efficient ways is a Sound Operating switch.

A Simple Sound Operated Switch Example:

A basic sound operating switch can be constructed using an audio amplifier IC, a comparator, a 555 timer operating in monostable mode, a relay and a load.

The audio signal is received by the microphone, which converts the audio signal to electrical signals . The signal is given to the pin2 of comparator IC 741. The other input pin 3 of the comparator is given by the reference voltage set by the potentiometer arrangement.

In absence of any audio signal, pin 2 is at logic high and the output of comparator is at logic low, giving a low signal to the trigger pin of the 555 timer. The output of the timer is thus at logic high, keeping the relay at off condition. When a sound is heard the microphone detects it and converts it to electrical signal and the signal is applied to pin2 of the comparator and since this pin is now at logic low , the comparator output is at logic high, triggering a logic high signal to the trigger pin of the timer. The timer output is thus at logic low, driving on the relay, which in turn switches on the load( A bulb) for a time determined by the RC combination.

Practical Sound Operated Switches Available:

Sound Operated Electronic Switch

It is a sound operated electronic switch kit by Electro Kits. It operates on a 9V battery and uses a electrets microphone. It switches on and off an LED mounted on the kit.

Automatic Voice Activated Switch:

Automatic Voice Activated Switch

Its switching time is up to 60seconds and supports loads upto 3A-115V or 5A-12V.

Clap On/Off Switch

It is a microprocessor controlled switch operating on 1 or 2 claps. It has a relay power rating of 24VDC/AC 3A. It works on a power supply of 12V dc.

 Sound Operated Switch

It is a 1382313 model number sound operated switch operating on a power of 250W max with a supply voltage of 120V. It works in two modes. In Home mode, it can operate one or two appliances. In the Away mode, it will operate on any noise to switch on the connected appliance