Overvoltage Protector with Relay

An overvoltage protector circuit is shown in the schematic diagram below. This circuit will work to disconnect the protected device from the power supply when an overvoltage occurs at the supply. This circuit uses a silicon-controlled rectifier (SCR) and normally-closed 12-V relay, K1. The silicon-controlled rectifier is connected in parallel to 12-V line to monitor for the overvoltage condition. This […]

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Transceiver Saver (Overvoltage Protector)

This is a transceiver saver circuit that protect  a transceiver device (applicable to other device as well)  from overvoltage of the power supply. This circuit is used to protect the device  by regulating the power supply,  avoiding damaging the device if overvoltage occurs.  If the transceiver transmits current of above 2A, a heatsink should be used for the transistor. The […]

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AC Line Dropout (Power Failure) Detector

Power dropout detection is often required by digital system driven from the AC line. A memory store command to be issued before DC power falls is allowed by fast AC line drop out detection. The circuit on figure below detects AC dropout by connecting an optoisolator across the power transformer’s rectified secondary. Normally, the LED is turned on by the […]

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Circuit Breaker

We can use a circuit breakers to limit the current in a single circuit in most household applications. Although breakers come in many sizes, typically a single circuit is limited to 20 amperes. This means that to bend it downward and release the spring-loaded trip-lever, 20 amps of current will heat the bimetallic strip. Another mechanism is employed to handle […]

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