Reducing energy consumption in home automation based on stm32F407 microcontroller
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nanomaterials-09-00813
| A. Hardware Implementation The implementation of the proposed solution is presented in Fig and is based on STM32F407ZG microcontroller from ARM Cortex ™ - M family. This microcontroller is the core of the Mikromedia 7 all-in-one board that has been used during the experimental setup of this project. The STM32F407ZG microcontroller is used to construct the subsystems of the home automation. In order to implement the temperature subsystem, digital DS18B20 sensors from Dallas Semiconductor have been used. These sensors can be controlled through Wire interface, meaning that a maxim of 64 sensors can be connected to this interface, bringing a further aspect to the low-cost desiderate. The experimental smart house where this architecture was tested, is fitted with an electric underfloor heating and cooling system which is equipped with piping and fans, therefore the control heating and cooling sources are formed only in electronic relays. Due to the fact that the control voltage is in the range of 3-32 VDC this relay can be actuated directly by the Mikromedia 7 development board. By using this type of relay, controlling the heating resistors can be realized in pulses. Since the heating system is the largest consumer of energy, by using this type of command and using the thermal inertia of the heating resistors, a discount between 15% and 20% of energy consumption can be obtained. This reduction can reach up to 40% by creating particular scenarios of the controlled areas (day-night, off days – working days, holidays. Due to the fact that the cooling sources are using low-power fans, low-power static relays were chosen as solution. The lighting subsystem fora certain area is formed by a NORPS-12 light dependent resistor, a HC-SR501 motion detector and a command relay, in our case 15.81 produced by Finder. The criteria for using these components is the cost, reliability and performance. The first component of the safety subsystem is the smoke detector MQ-2. Such a sensor is used both in household and industrial applications because it can also detect marsh gas, propane, butane, GPL, alcohol and hydrogen. As gas detector it is used a FCM6812 module offered by the Figaro manufacturer. This component is based on a catalytic gas sensor called Figaro TGS 6812 which provides a quick gas detection, being precisely calibrated during the manufacturing process. The provided output voltage is proportional to the amount of detected gas. To detect unauthorized opening of doors or windows the solution is based on a magnetic sensor. This sensor is composed of two parts, one part is mobile and one fixed. The moving part is a permanent magnet and in the fixed there is a reed relay. When the moving part is in front of the fixed part a logical "1" is sent to the central unit. When the mobile part moves, the reed relay switches off and a logical "0" is sent to the central unit. Since the heating system of the experimental smart house is of underfloor electric type, in order to protect the electrical circuits, in the case of high energy consumption, a current sensor has been used. The current sensor is based on an integrated ACS711 circuit that operates on the Hall Effect principle. This sensor has a voltage between 3 and 5.5 VDC and provides an output analogue linear voltage of 90 mV/A when powered at 3.3 VDC or 136 mV/A when powered to 5 VDC. It is designed for bidirectional input from - A to A. Fig. 1. Hardware implementation Authorized licensed use limited to Univ of Texas at Dallas. Downloaded on September 10,2022 at 01:29:13 UTC from IEEE Xplore. Restrictions apply. B. Software Implementation The software implementation flow is presented in Fig. 2. In order to lower the costs associated with the proposed home automation system, for the area where the central unit will be posted, we opted to use the Mikromedia 7 board’s temperature and PIR sensors. To read the temperature from the rest Wire sensors, first a temperature conversion command has to be sent, followed by a registers read command. After receiving this command, the sensor will send the values associated with the registers from the sensor’s memory. The used resolution is 9 bits, corresponding to 2 decimals. The actuators for the heating and lighting subsystems are formed of electronic relays. Therefore, these components are controlled by Pulse Width Modulation. This solution was chosen because is very useful for controlling the heating elements by reducing power and time consumption. This solution is very convenient for variable control of the lighting sources. The user interaction with the system is realized thorough a 7’’ touchscreen that comes as a component of the Mikromedia 7 board. The Human Interface module is realized in Visual TFT and its first screen offers the possibility of choosing the desired area. It can be Ground, Floor, Garage, Exterior and Settings. The Settings menu offers the possibility to set minimum and maximum limits for heating and temperature sensors that are mounted in a certain area, the user can set light scenarios, heating, irrigation, IP address for WIFI and Ethernet communication etc. The access to this menu is realized in a secured way in order to avoid the access of unauthorized persons to the entire home automation system. After choosing a certain zone in the first screen, anew menu will be displayed containing the selected part and the components of that area. IV. E XPERIMENTAL SETUP AND OBTAINED R ESULTS The experimental setup for this solution is a newly-built house (the construction was finished in 2008) which is situated in a four-season geographical area from Eastern Europe. In order to ensure the optimum temperature in the house, an electric underfloor heating system is mounted to the building. The costs associated with the solution presented in this paper (see Table 1) is approximately 275 Euros, placing this system in the category of low-cost solutions. TABLE COSTS ASSOCIATED WITH THE PRESENT SOLUTION Download 304.63 Kb. Share with your friends:
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