“This is a simple and fun project with pocket friendly budget.
Introduction
Capturing physical data in real time is always fascinating. In this project you will notonly be able to capture three fundamental physical parameters for weatherpredication viz. temperature, humidity and atmospheric pressure, but also beable to display the real time data on a LCD screen.
Description and Working Principle
The twosensors used in this project are BMP-280 and DHT-11. The former senses thetemperature and atmospheric pressure whereas the later senses the relative humidity.The DHT-11 could have been done with by using BME-280 (it can measure humidityalso) instead of the BMP-280, but if the cost is taken into account then usingthe combination of sensors used here is much more economical for DIY projects.It should also be noticed that although DHT-11 is capable of sensing bothtemperature and humidity, it is used for humidity sensing only because itstemperature sensing resolution is +/-2° compared to +/-.5° for BMP-280. The heart of this project is the Arduino NANOdevelopment board. Here also the NANO board has been chosen over the masspreferred UNO because of its affordable price. A 1.44” ST7735 series TFT LCDscreen is used as the display for our project. A bigger screen has been avoidedhere so that the Arduino NANO is not overloaded.
Circuit and Programming
Acombination of circuit diagram and block diagram has been provided asconveniently as possible to help the makers understand the physicalconfiguration and connection of the components. Tables for pin-out of thecomponents is also provided to make things easier. Going through the diagramand tables one will notice that the 5V and GND pins of the ICSP header onArduino NANO has been utilised for supplying power to the components along withthe on-board power and ground pins. This has been done to do away with anyadditional power source which will make the system bulky.
Coming tothe programming, in the first part an array of libraries have been included tokeep the programming short and simple. Besides the obvious ones, the Wire.h andSPI.h libraries are worth mentioning because Wire.h is the one that allows theArduino to communicate with the I2C/TWI devices such as the BMP-280 and theST7735 LCD and SPI.h provides the serial peripheral interface with the ST7735LCD. In the second part, the sensors are initialized and the layout, fontcolour etc. of the LCD are set up for displaying the data as per ourpreferences. In the final part of our programming, the output from the sensorsare obtained and displayed with a convenient delay between each reading to keepthings stable.
Construction and Testing
In theprototype, the components have been kept modular and connected using jumperwires instead of soldering. This not only allows easy troubleshooting andrepairing but also makes the assemby process hassle free. The device-case hasbeen custom 3D printed for a perfect fit for the components. The case isprovided with proper ventilation in order to expose the sensors to themeasurands and dissipate the heat generated by the system which will otherwiseinterfere with the sensing elements. The device is powered via the same type AUSB to type B mini USB used to program the Arduino. The prototype has beentested indoors at stretch for a few hours using both PC USB port and 5Vsmartphone charger as supply. The results are quite accurate compared withonline meteorological data, considering the production cost and developmenttime.
In conclusion it can be said that this projectis quite economical, useful to say the least, and most importantly, it is funhaving a small and handy weather station that fits right in your pocket.”