Whenever AC primarys provide fails, this circuit indicators you by using sounding an alarm. It additionally gives a backup light that might be useful you in finding your approach to the torch or the generator key in the useless of night. The circuit is powered directly with the help of a 9V PP3/6F22 compact battery. Pressing of switch S1 gives the 9V energy supply to the circuit. A red LED (LED2), along with zener diode ZD1 (6V), is used to indicate the battery energy degree.
Resistor R9 limits the running current (and therefore the brightness) of LED2. When the battery voltage is 9V, LED2 glows with full depth. As the battery voltage goes under 8V, the depth of LED2 lowers and it glows very dimly. LED2 goes off when the battery voltage goes below 7.5V. Initially, in standby state, each the LEDs are off and the buzzer does not sound. The 230V AC mains is directly fed to majors-voltage detection optocoupler IC MCT2E (IC1) by means of resistors R1, R2 and R3, bridge rectifier BR1 and capacitor C1.
Illumination of the LED within optocoupler IC1 activates its inner phototransistor and clock enter pin 12 of IC2 (connected to 9V by the use of N/C contact of relay RL1) is pulled low. Note that only one monostable of dual-monostable multivibrator IC CD4538 (IC2) is used right here. When primarys goes off, IC2 is prompted after a brief period decided via parts C1, R4 and C3. Output pin 10 of IC2 goes excessive to forward bias relay driver transistor T1 by the use of resistor R7.
Circuit diagram:
Resistor R9 limits the running current (and therefore the brightness) of LED2. When the battery voltage is 9V, LED2 glows with full depth. As the battery voltage goes under 8V, the depth of LED2 lowers and it glows very dimly. LED2 goes off when the battery voltage goes below 7.5V. Initially, in standby state, each the LEDs are off and the buzzer does not sound. The 230V AC mains is directly fed to majors-voltage detection optocoupler IC MCT2E (IC1) by means of resistors R1, R2 and R3, bridge rectifier BR1 and capacitor C1.
Illumination of the LED within optocoupler IC1 activates its inner phototransistor and clock enter pin 12 of IC2 (connected to 9V by the use of N/C contact of relay RL1) is pulled low. Note that only one monostable of dual-monostable multivibrator IC CD4538 (IC2) is used right here. When primarys goes off, IC2 is prompted after a brief period decided via parts C1, R4 and C3. Output pin 10 of IC2 goes excessive to forward bias relay driver transistor T1 by the use of resistor R7.
Circuit diagram:
Mains Supply Failure Alarm Circuit Diagram
Relay RL1 energises to prompt the piezo buzzer by means of its N/O contact for the time-out interval of the monostable multivibrator (approximately 17 minutes). At the same time, the N/C contact take aways the sure provide to resistor R4. The time-out interval of the monostable multivibrator will depend on R5 and C2. Simultaneously, output pin 9 of IC2 goes low and pnp transistor T2 will get forward biased to light up the white LED (LED1).
Light equipped by this back-up LED is sufficient to go looking the torch or generator key. During the mono time-out interval, the circuit will also be switched off by means of opening switch S1. The ‘on’ period of the monostable multivibrator is additionally changed by changing the worth of resistor R5 or capacitor C2. If majors doesn’t resume when the ‘on’ interval of the monostable lapses, the timer is retriggered after a brief prolong decided by way of resistor R4 and C3.
Light equipped by this back-up LED is sufficient to go looking the torch or generator key. During the mono time-out interval, the circuit will also be switched off by means of opening switch S1. The ‘on’ period of the monostable multivibrator is additionally changed by changing the worth of resistor R5 or capacitor C2. If majors doesn’t resume when the ‘on’ interval of the monostable lapses, the timer is retriggered after a brief prolong decided by way of resistor R4 and C3.
Source: EFY Mag
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