While completing a coursework on MSc, Peter Haban developed a WSN which he later used for his Arduino controlled greenhouse project. It is an energy efficient network based on the Arduinos and XBee ZNet 2.5 modules. Before proceeding, it’s important to get a brief idea about a Wireless Sensor Network. In this system, there are various spatially distributed autonomous sensors that monitor the environmental conditions like temperature, sound, etc which is passed to the main location. It was primarily developed for the battlefield surveillance but nowadays it is used for various industrial and consumer applications.
In this DIY project, the network collects different environmental readings with the help of 3 sensor nodes that submit soil moisture, humidity, temperature, etc. Apart from these, he developed a concentrator node to upload data sets on database, an LCD node to display datasets on LCD and an actuator node that extracts temperature values and denotes them by turning on the LEDs/fans. The main components utilized in building this network are- sensors, nodes, Arduinos, XBee, Ethernet and Flot.
Moving on to the database, Peter stored it in a single table as he was unaware of the amount and kind of data. However, as there are different nodes that render a separate kind of dataset, one needs to make a different table for the data submitted by each node. After this, he wrote two PHP scripts to enter the sensor readings into the database table so as to extract the data and display it on LCD.
Further, when it came to XBee network, it could be used without Arduino but as he wanted to read multiple sensors with each node, he decided to base each of them using one Arduino and one XBee shield. Then in order to communicate with the XBee modules, he chose the API firmware which suited the needs of the project.
Peter used 5 sensors in the network for determining temperature, humidity, soil moisture, light and water level. Then he placed all these sensors in a soda can with a 12V fan mounted at one end to suck the air. Lastly, in order to save power during the delay phases when the Arduino board is idle, he made use of ATMega as it is quite energy efficient. As per Peter, the idea of writing the system himself allowed him to gain a valuable experience during the project and he was able to make it more power saving. Moreover working with a cross-platform allowed him to replace a lot of components without actually intervening with the design of the system.
As an improvement, Peter also suggested that although Arduino is quite convenient for prototyping, it would be wiser to replace it with a Waspmote. It uses an optimized platform and at the same time renders benefits like power efficiency, certification, range, and standardization thereby making it a feasible option for the commercial and industrial use.
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