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  • Shadow Sensor Alarm

  • Created: Mar 16, 2014

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Description

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Summary

This project is a simple alarm system that uses MCP6001 low power operational amplifier which has a gain bandwidth of 1MHz with 90 degrees phase margin. The device can ideally be a burglar alarm that produces a loud tone when discrepancy of light is detected. As much as the circuit is highly sensitive and prominent that it can detect shadows from a certain distance, it is also portable that it can be placed anywhere for monitoring.


Shadow sensors are widely used to detect the movement of a person in a confined area. Many circuits published earlier have a serious drawback that only one light dependent resistor (LDR) is used for shadow detection. Needless to say, this is not a perfect solution!


Described here is a simple but improved circuit of a smart shadow sensor alarm, which can register a shadow when there is a light difference. Here two 5mm LDRs are used with the popular Op-amp MCP6001 to drive an active piezo-sounder when a “valid” shadow is detected. The whole shadow sensor circuit can be powered from four 1.5V AA cells (6VDC), or similar dc supply sources.