1. Introduction

The proposed design is a star network of outdoor wireless sensor nodes spread across the specified one square kilometer of the urban area for monitoring air quality of the environment. The sensor nodes consist of sensors for monitoring CO2, CO, NH3, Benzene, LPG, Smoke etc. The proposed design uses ambient air monitoring to get the clues as to where the pollution is coming from and what is its level which will be helpful in reducing the emission and making the environment healthy. The proposed design uses stationary deployed sensors across various parts of the defined area which gives the exact details of the pollution levels.

The proposed design uses LoRa (Long Range) technology based sensor nodes equipped with sensor, Li-Po battery, solar panel, and circuitry to charge battery and supply required voltage to MCU. The proposed design prefer LoRa over WiFi and GSM/GPRS because WiFi have range issue, uses more power and may not be always available outdoor. GSM is expensive and power hungry. LoRa technology serve long range and is also low cost and low power consumption suitable to run device on battery for long time. The range of 5 km can be easily achieved using LoRa. Therefore LoRa is suitable for our design.

2. How does the design work?

The working of proposed design is fairly simple. As per requirement, various LoRa powered sensor nodes are deployed in the specified area which sends data to a centralized gateway node located at the highest place at some center point in that area. The gateway node is always connected to power source and Internet to transmit data further to IoT cloud server. As shown in Fig. 1 the gateway receives packets from each sensor nodes and uses MQTT protocol to transmit it further. The MQTT is another lightweight protocol designed for M2M communication which increases transmission speed and data security and reliability.

The main actor in the design is IoT sensor node. For making a sensor node run on battery for a year it uses LoRa module which require less energy. But there are other components that consume battery like the MCU itself, and sensors attached to it. Therefore as in Fig. 2 this design uses Li-Po rechargeable battery attached with solar panel and control circuitry in order to make sure that once deployed the sensor node never fails. This design uses FireBeetle ESP32 MCU by DFROBOT which is specially optimized ideal solution for IoT low power consumption projects. The sensor node sends data and sleep for 60 minutes when no transmission or sensing is required. It sense and transmit only when it wakes up. Here we assume that the sensor node need at least 30 seconds for the sensing and transmission process. The proposed design uses 6600 mAh battery, run code for 30 seconds and sleep for 60 minutes. It consumes 300 mA in working mode and 700 µA in sleep mode. This gives more than two months of battery, but since the battery is charged by solar panel it can easily run sensor node for a year and more than that depending upon battery recharge cycle. We call our approach “install and forget” since it can run a year without interruption.

3. What makes it innovative?

The problem with LoRa is that it transmits data and forgets. Therefore there is no mechanism to check if the data is successfully delivered. To overcome this problem the proposed design uses a special message format which allows gateway to identify the data and send acknowledgement to sending sensor node.  Proposed system also provide forecast of the gas level based on historical data received.

4. How would it be produced?

Sensor nodes can be easily produced by assembling the already available components in the market. A single sensor node device requires less than $50. Gateway node can be implemented using Raspberry PI development board. Since it is based on LoRa no additional components are required to establish a network. The gateway node only needs LoRa module and Internet connectivity which can easily be made available.

5. What its potential impact would be around the globe?

"Information is everything" based on this theme the system plays an important role in identifying the polluted area based on collected data which is required for taking necessary action in reducing the pollution of that area thus help in making healthier environment. The citizens can also use the app to get information about area specific pollution and take necessary precautions themselves. System also generates alerts if the value of gases is above threshold. The system also delivers information to the general users about the harm causes by various gases along with its level to impart a general awareness thus making a potential impact around the world.


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