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Applications Of 555 Timer

Missing Pulse Detector : This circuit is one shot and it is continuously retriggered by the input pulse train. A missing pulse can prevents retriggering before completion of the timing cycle. Then output will be low till a new input pulse arrives and continuous alarms will be developed for a missing pulse.


 Electric Eye Alarm:  A light dependent resistance (LDR) is used to sense light. When light falls on the LDR, it will be shorted and the timer circuit will be reset. The pitch of speaker can be controlled by varying resistance R2.


 Dark Detector:  It is used to detect darkness all of a sudden. The light dependent resistance (LDR) is used to detect darkness or illumination below a limit value. Due to absence of light, LDR will be short and circuit will be reset. Then speaker develop the alarm.


 Metronome:  Metronome is used in the music industry to produce the rhythm by a ‘toc-toc’ sound. The speed of sound can be adjusted by the potentiometer R1 . 

10-minute Timer: This circuit can be used as a time-out warning at every ten minutes. It is difficult to keep track of time for longer duration. When the reset switch is pressed, the green light (D2) ON and time cycle will start. After 10 minutes, Red light (D1) will be ON to warn the operator for specific operation.


Schmitt Trigger: It removes any noise signal in input and it generates square wave output signal.


Pulse Sequencer:  Sometimes, the sequence of pulses are required in certain digital circuits. The pulse widths may be equal width or unequal width, but they must comes one after the other. Generally, pulse sequencer is used to generate a series of pulses in time sequence. 

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