Summary of the circuit
Power Supply Resumption Alarm circuit will give you sound effects and visual effects at the time when power resumes.
The power fluctuations may damage your electronic devices like TV, Fridge, etc. For this we have used power stabilizers, but they are costly and power consuming too.
This circuit is less costly to construct also consumes less power.
This circuit needs only 9 V to work.
Principle behind Circuit
The circuit which is shown here is easy to configure. In this circuit IC1 is mounted in an unusual mode. When power resumes, pin 2 of IC1 which is connected through capacitor C1 is grounded and goes low while pin 3 of same IC switches to high. In turn pin 4 of IC1 which is a reset pin, switches to high state for approximately 10 seconds. When the voltage at C1 reaches to 2/3 of the supplied voltage, capacitor starts discharging and output switches to low, grounding the pin 4 which is a reset pin and hence the fallen circuit moves out of action.
Alarm circuit is made up with the help of second IC i.e. IC2. Astable mode of this IC is used in this circuit and the working frequency of the IC is 1 KHz. At the time when the output at IC1 is at high state, IC2 comes into action.
So the speaker will generate the alarm for approximately 10 seconds. After this time duration, IC1 switches back to its stable state. With the help of pin 7, capacitor C1 quickly discharges and for the circuit all set for the next recognition, as the pin2 of IC1 is at low state. So when the supply breaks off for the next time it will generate a sound. LED is used in the circuit to provide a visual effect.
Components required building the circuit
LED1 Any colour
Power Supply 9V
Fig. 1: Prototype of 555 IC based Power Resumption Alarm Circuit