In households across the world, electricity is wasted when devices plugged into outlets are on when unused. Instead of diligently turning devices on and off for periodic use, people often find it easier to leave electronics on for extended periods of time, whether it be an air conditioner, heater, television, humidifier, or lamp. In addition, it is even more difficult among groups like the elderly and those with disabilities to be conscientious about actively switching their devices on and off.

To combat this issue, numerous Internet of Things (IOT) "smart" plugs and switches exist, but these products require frequent monitoring, possess extremely limited applications, and actually waste energy themselves- the popular Wemo Smart Plug consumes 1.5-2W. As these devices gain popularity, IOT's carbon footprint continues to grow.

I sought to combat these issues by creating a power efficient Modular Sensor Switch (MSS) that gathers data from its surroundings using sensor modules to autonomously switch the power of appliances. Being conscious of energy efficiency, I used an Arduino Pro Mini as the microcontroller connected to a HC-06 bluetooth module for users to communicate with the MSS through my Android app. I worked with six sensor modules that detected light, motion, dangerous gases, infrared remote signals, temperature & humidity, and sound. Rather than relying on restraining timer-based switching and energy-draining remote switching in traditional smart plugs, the MSS uses these factors to determine the switch's state.

The device not only makes it easier to save power, but has potential to serve as a safety device. By applying sensor modules like smoke and motion detectors to the switch, the switch could turn on a speaker or strobe a light when poisonous gases or home intruders are detected. The latter method of alerting users of threat is especially practical for those with hearing impairment.

IOT devices consume excessive power because they are constantly connected to a network, so the MSS actively turns off the Bluetooth module with a transistor after the user finishes modifying its settings in the app. At this point, the MSS becomes autonomous, and users no longer need to interface with it in my app unless they are changing the sensor module or its sensor thresholds.

I tested the energy consumption of the MSS in various positions with a variable power supply; it uses 55mW with no sensor when the relay is open, which is approximately 3.66% of the Wemo Smart Plug's 1.5W. When the relay is closed, which is typically the minority of the time, it uses 380mW, or 19% of the Wemo's 2W. The average sensor accuracy, calculated by recording the times the switch triggers upon the occurrence of a trigger event in different settings, is 93.4%, which is promising for a prototype, as it demonstrates that using one system to employ drastically different sensors is a viable model.

Although there are possible further power improvements, like using Bluetooth 4.0 or a latching relay, the MSS model can still save energy in a variety of applications, and has numerous features like error detection in sensor data processing, switching Bluetooth communication, and real-time sensor feedback in the mobile app. From start to finish, I designed every component of an automated switch -the electrical board, Android app, Arduino program, and the enclosure- that outperforms popular industry smart plugs in low energy consumption by more than 25 times in its open state while possessing a plethora of applications.