Energy Harvesting Air Quality Sensors

Introduction

Air pollution has taken a toll on everything around us and we seldom realize how our action effect the environment. This project was aimed to create a system of wireless, self-sustained sensors that can monitor air quality out doors and in doors. The initial plan was to create a solar harvesting system that would power the node and it could connect to a gateway device that would intern send data from multiple nodes to the Sierra Air Vantage Cloud. More nodes could be added as per requirement. A secondary standalone unit was also proposed that could be used as an indoor sensor node and could provide indoor air quality information via the Air Vantage Cloud service. The sponsors Element14, Texas Instruments, Wurth Electronics, Eclipse IoT and Sierra Wireless provided support along the way. A diagram of the proposed system is given below.

diag1

Work Plan

The entire project was done in phases since it had some hardware and software components. On the hardware side, TI had proposed some components such as BQ25504, HDC1000, TPS62740 and TPS61200 to name a few for use in the design. The entire system was divided into submodules as explained in the proceeding sections. Additionally, I created some tutorial like posts which I will index in one of the proceeding sub-sections.

A list of submodules is as follows

  • Energy Harvester Module based on the TI BQ25504 and a SuperCap
  • Energy Efficient Wireless Sensor Node based on the TI CC110L and FR5969
  • Gateway device Based on the BeagleBone Black
  • Standalone Sensor Node based on the TI CC3200
  • Connectivity with the Sierra Air Vantage cloud Service.

Not all modules are finished but there are lessons learned which will influence future work.

Additionally it took me a lot of time to research sensors as many sensors in the market are NOT suitable for outdoor usage as per manufacturer recommendations.

Energy Harvester Module based on the TI BQ25504 and a SuperCap

One of the requirements of the Design Challenge was that the sensor nodes should require least bit of human intervention. Additionally, we were instructed to use certain parts such as the BQ25504 which is a energy Harvesting IC and hence a module was designed around it and TPS62740 and TPS61200 which are voltage regulators. The deviation from conventional design was to use a SuperCap instead of a battery and use the energy efficient MSP430FR5969. Hence I designed a circuit using Eagle CAD, got the passives from Wurth Electronics, Element14 and chips from TI as samples. Some parts arrived around two weeks from the dealline leaving very limited room for testing. Additionally the BQ25504 was so small that soldering it was a challenge but completed successfully. The result is shown in the image below.

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It works to some extent but I had some minor issues as shown in the video below.

I want to assemble some more boards and experiment before I move on and that will take some time mainly because I have run out of chips and will request TI to supply some more. I am sure I can get it to work and will update once I do.

This module is hence parly complete due to lack of time and timely delivery of some passives.

Energy Efficient Wireless Sensor Node based on the TI CC110L and FR5969

This part is quite simple and is mainly a software segment. I used the FR5969 Launchpad along with Air Booster Packs to fabricate a wireless sensor node. With my unsuccessful attempt at making the Energy Harvester, I moved to use the TI Fuel Booster Pack and connected a solar panel to it. The code was written entirely in Energia which makes prototyping quick. There was a requirement that the system should “Sleep” when not transmitting. For this LPM3 was used along with a timer and interrupts to make sleepy delays possible making the node more energy efficient.

A potentiometer is used in place of a sensor. As a bonus, I used the TI HDC1000 and soldered on by hand. The result is as follows.

IMG_20150119_225845

I got it to work using a buspirate but since I have to use softI2C on the FR5969 there is still a bit of debugging to be done. Just a matter of time.

This module is complete with the absence of sensors which have yet to arrive. I hope the sensor module comes through as I would like to finish this project in the future.

Gateway device Based on the BeagleBone Black

A BeagleBone Black gateway is used to send data to the AirVantage Cloud for logging. I was able to put together a custom setup with a NodeJS script to connect to the AirVantage Cloud and I wrote a tutorial in the process so that it may be useful to people in the future. Additionally, I made an Additional launchpad a wireless receiver based on the CC110L and it captures all the information from wireless node and funnels it to the BBB via USART. This data is conditioned and sent via Javascript(NodeJS) to the cloud service. The image of the setup is given below.

IMG_9565

This module is also complete to the original intention.

Standalone Sensor Node based on the TI CC3200

One of the targets was to have a standalone Wireless Node which did not require a gateway. This is useful where only a single node is required or nodes spaced far apart are required. I used the CC3200 LP to accomplish this along with a Fuel Booster Pack. Again since the sensors are not yet available, a demo system was constructed. The code was written in Code Composer Studio and the system can talk to the cloud via MQTT. Since this node is designed to be an indoor unit, the charging can be done manually. In this case, it happens via Wireless Charging using the Wurth Electronics Wireless Power Design Kit(which I got in a previous Design Challenge. The result is shown in the following images

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The basic system is working but I am using the onboard temperature sensor and logging the Fuel Tank values of Time to Empty and Time to full via MQTT. The base is ready and working.

Connectivity with the Sierra Air Vantage cloud Service

I managed to connect to the Air Vantage Cloud via MQTT and wrote a little bit about it. There is not much to it, but I hope my writing helps other in the future.

Conclusion and Future Work

Lots needs to be done at this point since I blew up some parts and got the circuit working a bit too later. Time was a crunch factor and I have learned a few lessons on project management. I will be continuing this project at my pace post challenge deadline since I want to have a project like this added to my porfolio. I am waiting for sensors to arrive and will be requesting TI for more samples. The harvester will also get an upgrade from it’s current 0.1Farad SuperCap to something bigger. Every component needs a better enclosure and I hope to have some more PCBs in the future which have sensor circuits on them.

Additionally, I am studying Eclipse KURA as a gateway platform but I am not using it until I understand it a bit better. I am an EEE engineer and so my Java skills are a bit limited.

At the time of posting this Summary, I am working on more tutorials as I work.

Build Logs

The entire build log of posts can be found HERE

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