Build Your Fridge Door Alarm Circuit – 20 Second Alerts

Description

This circuit, housed within a compact enclosure, is positioned within the refrigerator alongside any present illumination source. With the cabinet’s door securely closed, the internal environment remains dark, leading the photoresistor R2 to exhibit a high resistance (up to 200K), effectively maintaining pin 12 at a high state and thereby safeguarding IC1. Upon the entry of a light beam via the opening or the activation of the refrigerator’s lamp, the photoresistor reduces its resistance (below 2K), causing pin 12 to drop to a low level, initiating the counting sequence of IC1. Following a pre-determined delay period (20 seconds in this particular instance), the piezo buzzer emits a sound for 20 seconds, after which it enters a quiescent state for the same duration, and this cycle repeats continuously until the refrigerator door is closed. D2 connected to pin 6 of IC1 facilitates a 3 kHz oscillation within the piezo buzzer.

Circuit Diagram:

Parts:

Integrated Circuits Details

The 4060 Ripple Counter & Oscillator IC (IC1) is a versatile integrated circuit widely utilized in timer and counter applications. It’s primarily designed to function as a ripple counter, providing a simple and efficient method for generating timed delays. This particular IC incorporates an oscillator, creating a stable clock signal that drives the counting process. The 4060 IC features six inputs and six outputs, allowing for flexible configuration and adaptation to various circuit requirements. Its operational modes include the ability to generate precise delays, provide pulse outputs, and function as a binary counter, rendering it an invaluable component in numerous electronic projects.

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