On 13th Aug 2014, the Yuktix team visited a greenhouse about 20 kilometers away from Bangalore on the border of Karnataka and Tamil Nadu to conduct a Wireless Sensor Network experiment.
Objective of the Experiment: To test the LOS and Non-LOS range of the wireless Zigbee modules that Yuktix planned on using.
But why to test? The specifications of any module as listed on its box are usually a number that the manufacturers have arrived at by testing it under laboratory conditions. To test the real efficiency of any system, it must be tested out in the field away from resources.
In the same greenhouse we had already deployed our Yuktix Wireless Data logger which continuously sends to the Yuktix IoT Device cloud. All reading logged through this data logger can be accessed in real time from anywhere over the Yuktix IoT Cloud and also over the Yuktix android app. One can also configure notifications based on device rules that can be easily set over the Yuktix dashboard.
We planned to measure the temperature and humidity of a greenhouse chamber where that logger was installed and in the process test the range of our wireless module and the power consumption characteristics of the wireless sensing-cum-transmission module. We decided to use Zigbee for wireless communication for our WSN experiment instead of going with RF modules as they are prone to noise. The interior of a greenhouse is a high humidity area with foliage obstructions where foggers and mistifiers operate thus more than any physical obstructions, the water-vapour can add to the noise.
The experiment configuration consisted of
- 3 edge sensing nodes equipped with sensors and our Zigbee module,
- 1 repeater(coordinator) with the Zigbee modules
- 1 control unit or master, that is our Yuktix Datalogger which was also equipped with Zigbee modules
We plugged a temperature and humidity sensor to the Yuktix Datalogger. Then we took the master module (attached to the laptop), and carried it across the field. The module manufactures usually claim that the module would work on the field with a 1-2km range, but in our experience, that rarely happens. Without a patch antenna, it would hardly go beyond 500m. We tested the modules in our office and got a range of 50m (Non-LOS). When we tested out the same in the greenhouse we got a range of 300-450m which was satisfactory for us.
We repeated the experiment with soil temperature and humidity sensors and Lux sensors and found similar satisfactory results.
Along with testing the module range we were also able to ascertain that power consumption levels of our chamber transmitter modules were very low and hence extremely satisfactory for on-field deployment. Our edge-sensing nodes are low power consuming transmission nodes, which go in sleep mode after sending the data to the master.
We propose a wireless sensor network solution for the Greenhouses to monitor internal environment data over the cloud. The units deployed in the greenhouse would be a combination of wired and wireless units (based on locational convenience) which would locally relay greenhouse data over Zigbee mesh network or over wired lines. The gateway nodes would transmit this data over GSM to the cloud from where the entire environment of a geographically spread greenhouse system can be monitored from one single dashboard.
The same data can very easily be displayed over LED TV monitors outside the greenhouses for the benefit of the greenhouse managers. This monitoring system can be extended to automate the greenhouse equipment based on the rules that we set for sensor-data ranges. We can automatically power on mistifiers and foggers when humidity levels drop below predefined levels, or power them off when they exceed the defined level. Grow LEDS can be powered based on Lux measurements as can irrigation valves based on soil moisture. In short the entire array of greenhouse equipment can be automated based on the sensor data and can be remotely controlled and monitored over a remote dashboard.