Monday, September 9, 2013
Sunday, September 8, 2013
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
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