Solid state voltage indicator with high voltage cutout

Posted on Feb 7, 2014

Voltage fluctuations in the mains are very common phenomenon. These fluctuations can cause heavy damage to costly electronics and electrical gadgets operating for long period of time. For such purpose, an automatic stabilizer is used which is usually quite expensive. A costly voltage stabilizer can be replaced with this low-cost Solid-state Voltage

Solid state voltage indicator with high voltage cutout
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Indicator with High Voltage Cutout  circuit. It can also be used to convert a manual stabilizer into an automatic one. It performs three functions in different conditions. X1 is a voltage step-down transformer that steps down 220V AC to 18V. This voltage is filtered and rectified by C1 and D1 respectively. As the output of the transformer is not well filtered and regulated, the output will be proportional to the input. VR1 is adjusted to operate the relay at a particular voltage higher than the output voltage of the transformer at normal mains level. So, when the mains voltage increases, the output of the transformer also increases. Zener diode ZD2 starts conducting and provides bias to T1 which starts conducting. This in turn energizes the relay and light up the RED LED (LED1), to indicate a high voltage. Diode D6 provides protection to the relay against induced voltages. IC LM741 (IC1) forms the heart of the normal and low voltage indicating circuitry. The potential of the non inverting input serves as the reference voltage across zener diode ZD4. Variable resistor VR3 set the DC gain of IC1. LED D5 is connected between the output (pin 6) and the positive supply. R5 limit the current going to diode LED5. Under normal conditions, the voltage as the inverting input will be higher than at the non-inverting input. So the output will be low, ad LED5 will remaining glowing. But, when the mains voltage drops, the voltage at...

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