# Development of an Energy-Efficient Smart Socket Based on STM32F103
## 2 Literature Review
In this study, a multiple-sensor network was also employed to monitor the energy consumption of appliances. Studies reviewed by [PERSON] et al. also indicated that multi-sensor systems could improve the accuracy of energy consumption prediction, but suffers from higher system cost and operational energy consumption issues [1]. In another word, the sensor-network based intelligent systems can provide high precision detection and implement accurate energy-efficient control. However, the associated energy consumption of systems was commonly underestimated or even overlooked. Therefore, with the integration of multiple sensors and required devices for the measurement of temperature, distance, position and environmental lighting, the associated energy consumption might also need to be considered to avoid improving one element at the cost of another one. In the recent years, WIFI, ZigBee, Bluetooth technologies and Internet of Things (IoT) have also found a wide application in the development of energy-efficient control systems and smart sockets. Regarding the different communication manners, intelligent plugs based on Wi-Fi connection were discussed in the literature [16; 17; 18]. Reference [16] introduced the development of a smart plug built on a low-cost Wi-Fi controller composed of a microcontroller and a Wi-Fi module. Reference [17] demonstrated another Wi-Fi based intelligent socket which was built on an MSP430 microchipcontroller. This system can be remotely set and operate with two modes, the normal mode and a timing mode. In addition, overload, overvoltage and overcurrent protections were integrated to address safety concerns. There also some smart plugs like the OMG (Object Management Group) in Reference [18] and Wi-Fi kamkunit in Reference [19] were developed to power on/off appliances via Wi-Fi communications. Bluetooth is another communication technology which is widely applied in smart socket development. A solution was proposed in Reference [8] to control and monitor home appliances by using a Bluetooth low energy (BLE) smart plug as a referent device. The application can be implemented on Android OS to extend its remote operation. Another power outlet system that uses Bluetooth is detailed in [20]. This study proposed a smart office energy management system which can intelligently control the power of PC, monitor, and lights through a location-aware approach based on BLE beacons, smart plugs, and a mobile app. Recently, Zigbee technology has also attracted wide attention in intelligent sockets design. In a study conducted by [PERSON] et al., a ZigBee-based energy measurement and communication unit was integrated to monitor the energy consumption of home appliances and lights [21]. Reference [22] combined Zigbee with Internet protocols to carry out both remote and on-site power on/off control and measure the current of home electrics. A similar study was conducted, in Reference [23], where end-users can easily turn on/off the home appliances by connecting the appliances to the smart plug with ZigBee communication. While Reference [24] presented the design and implementation of a ZigBee-based smart power socket system with functions, including remote control, energy consumption monitoring, overconsumption control, vampire currents detection and the avoidance of electrical fires and shocks. The IoT-based structures presented in the Reference [25] interact with the surrounding environment in terms of sensing and metering, processing this information to extract knowledge for optimizing energy efficiency at the demand side. [PERSON] et al. shows the benefits and opportunities that IoT technologies can provide for the internet of energy. The combinations of WIFI, ZigBee, Bluetooth and IoT technologies have increased the intellectualization of appliances and brought more convenience to the end-users. However, intelligent products with complex functions and require more difficult operations might affect the user experience, which will correspondingly limit the application of products.