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Chill Out Loud Schematic Circuit Diagram

The Frustration of the Bouncing Fridge Door

Everyone encounters the common issue of a refrigerator door bouncing open slightly after being casually closed. Often, the barely noticeable gap is enough to activate the fridge light, leading to unnoticed spoilage of food, especially when one is away for extended periods.

Crafting a Low-Power Solution with TEMT6000 Phototransistor and PIC12F629

Frustrated with returning home to spoiled milk and questionable chicken, the author devised a solution using readily available components. Leveraging the sensitivity of the TEMT6000 phototransistor to visible light, the circuit ensures the fridge light activates even with a minimal 2 mm door opening. To maintain minimal power consumption, the design incorporates the PIC12F629 microcontroller with its low-power “sleep” mode, utilizing its internal RC oscillator and optimizing power settings. By carefully configuring the microcontroller and choosing appropriate components, the circuit achieves remarkable efficiency, consuming as low as 1.2 nA of current in Sleep mode, making it ideal for battery-powered applications.

Chill Out Loud Schematic Circuit Diagram

Lithium Cell CR2032/1HF: Longevity and Efficiency

The CR2032/1HF Lithium cell, boasting a capacity of 230 mAh and a nominal voltage of 3 V, offers exceptional longevity. Considering typical sleep mode currents, this battery can last for over 250 years, effectively matching its shelf life. This impressive duration makes it an excellent choice for soldering onto a PCB, ensuring power supply reliability.

Piezo Sounder: Efficient and Easily Driven

Utilizing a piezo sounder, such as the Kingstate KPEG827, proves to be a cost-effective solution. This device can be directly driven from a PIC across two ports, withstanding 3 Vp-p drive effortlessly. The PIC program, developed using MikroElektronika products, keeps the design simple and manageable.

Adjustable Alarm System with Low Power Consumption

The system’s alarm delay, adjustable from 1 to 255 seconds in software, ensures flexibility. Triggered, the unit consumes approximately 500 μA for a 1-minute timer period, doubling when the sounder operates. Despite this, it remains well within the maximum current limit of the CR2032 cell (10 mA max. pulsed). Even with the fridge being opened 20 times a day, the battery life still hovers around 9 years, showcasing the system’s efficiency.

Compact and Practical Design Implementation

The compact circuit design, demonstrated in a prototype by Elektor Labs, can be easily housed in a small ABS case. The ambient light sensor, like TEPT5600, is integrated to detect light sources. Ensuring proper installation, such as doubling the value of R1, enhances its functionality. The unit can be conveniently mounted inside the fridge, and it activates the alarm only when light is detected, ensuring an energy-efficient operation.


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