Mains Supply Failure Alarm



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:

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.

 

 

Source: EFY Mag

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Mains Pulser

The pulser is intended to switch the mains voltage on and off at intervals between just under a second and up to 10 minutes. This is useful, for instance, when a mains-operated equipment is to be tested for long periods, or for periodic switching of machinery. Transformer Tr1, the bridge rectifier , and regulator IC1 provide a stable 12V supply rail for IC2 and the relay. The timer is arranged so that the period-determining capacitor can be charged and discharged independently. Four time ranges can be selected by selecting capacitors with the aid of jumpers. Short-circuiting positions 1 and 2 gives the longest time, and short-circuiting none the shortest.

Mains Pulser Circuit diagram:

In the latter case, the 10µF capacitor at pins 2 and 6 of the timer IC determines the time with the relevant resistors. The value of this capacitor may be chosen slightly lower. The two preset potentiometers enable the on and off periods to be set. The 1k resistor in series with one of the presets determines the minimum discharge time. The timer IC switches a relay whose double-pole contacts switch the mains voltage. The LEDs indicate whether the mains voltage is switched through (red) or not (green). The 100mA slow fuse protects the mains transformer and low-voltage circuit. The 4 A medium slow fuse protects the relay against overload.

Source :   http://www.ecircuitslab.com/2011/05/mains-pulser.html

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