You might have seen so many applications and circuits based on monostable multivibrator using IC555 like intruder alarm, automatic night lamp, smoke detector, fire alarm, automatic gate controller, object counter etc. In all such circuits monostable multivibrator is used. We may easily understand the operation of the circuit but many of us don’t know how such circuits are designed. So here I will try to explain how such circuits are designed using some examples.To detect the light we need any photo sensor and the LDR is one of the most convenient photo sensor. It works on photo conductivity principal. That means its resistance varies as light falls on it. In absense of light the resistance of LDR is maximum and as light intensity increases the resistance decreases. So we can use this property in designing this circuit. As the resistance of LDR changes, the voltage across it also changes and this voltage is used to trigger monostable multivibrator.
Day and Night Indicator using IC 555
The main aim of the Day and Night Indicator project is to help us to turn on the lights as the night falls automatically and as the dawn sets in the Day and Night Indicator automatically gets switches off the light and plays a musical morning wake up alarm. Another feature of the project is that at the time of no light in the room during night the night lamp gets turned on automatically. With the help of this circuit you are not required to switch on or off the lights in nights or in the morning.
Magic Eye using 555 Timer IC
This circuit is based on a LDR which act as a sensor to detect the shadow; NE555 is a timer IC and UM66 which is used as melody generator IC. The circuit woks on the principle of operation of LDR (light dependence resistor). LDR is a device whose sensitivity depends upon the intensity of light falling on it. The resistance of LDR decreases when intensity of light falling on it increases and vice versa (resistance increases when intensity of light falling on it decreases). In dark or in absence of light, LDR exhibits a resistance in the range of mega ohms, which decreases to a few hundred ohms in presence of bright light. Magic eye can be used as automatic guest indicator in your home. Just install this at the bottom of the door and whenever a person comes at door its shadow will fall on light dependent resistor and will ring the bell.
Servo Motor Control Using 555 Timer IC
Normal DC motors just require power supply(+V and GND) and are controlled by switching it ON/OFF or by varying the amount of power supplied to it but in case of servo motors we generally need a microcontroller to control them since it needs a special signal along with the normal power supply(+V,GND and SIG). This circuit will show how to control a servo without using a microcontroller. The circuit uses a 555 Timer IC which is very cheap when compared to a microcontroller and also which doesn’t require programming. The 555 IC is configured in Astable Mode to generate the “Special Signal” for the servo motor to work. First let us understand that signal. Here the special signal is nothing but a Pulse Width Modulated signal usually with a frequency of 50Hz (i.e. a Time Period of 20msec) or 25Hz (Time Period 40msec).
Designing Interesting Applications with IC555 Monostable Multivibrator
You might have seen so many applications and circuits based on monostable multivibrator using IC555 like intruder alarm, automatic night lamp, smoke detector, fire alarm, automatic gate controller, object counter etc. In all such circuits monostable multivibrator is used. We may easily understand the operation of the circuit but many of us don’t know how such circuits are designed. So here I will try to explain how such circuits are designed using some examples.To detect the light we need any photo sensor and the LDR is one of the most convenient photo sensor. It works on photo conductivity principal. That means its resistance varies as light falls on it. In absense of light the resistance of LDR is maximum and as light intensity increases the resistance decreases. So we can use this property in designing this circuit. As the resistance of LDR changes, the voltage across it also changes and this voltage is used to trigger monostable multivibrator.