Carbon Footprint Monitoring - Architecture

In this post, I will share a very high level architecture of the system and a brief description of its subsystems in the section below.

The subsystems can be classified into five: (1) Indoor sensors, (2) Outdoor sensor, (3) Central Hub, (4) [Vehicle] Emission Sensor and (5) Cloud Platform.

1 Indoor Sensors

The indoor sensors include:

(a) Smart plug - this particular unit would be similar to a conventional wall socket unit, but with a built-in power consumption monitoring module.  An ACS712 current sensor will be used to monitor current consumption.  The smart plug will be connected to the home network wirelessly and can be remotely controlled and managed.  Being wirelessly connected, the CC3200 will be the suitable component in the management and control of this sensor.

(b) Smart Switch - similar to the Smart plug, this is pretty much the same as a conventional light switch, but (again) with a built-in consumption monitoring module and an ambient light.

(c) Environment Sensor (Indoor) - having the looks of a smoke alarm system, this module is equipped with additional sensors such as: an air quality sensor, a temperature and humidity sensor.  This sensor will be battery powered, thus an ultra-low power MCU is required to be the brain for this device, at the same time will require to have a wireless interface for it to connect to the home network.  Battery should last at least year before replacement and should inform the user of battery status and notification on low battery state.

Each sensor unit will wirelessly transmit their status to a central hub.  The power consumption reported by these sensors will be used towards the "carbon budget".

2 Outdoor Sensor

This sensor is to be mounted outside the house that will monitor outside temperature, humidity, external light, and an air quality sensor as well, which will be used as differential air quality monitoring.  The outdoor sensor, as with internal equivalent, will be connected to the home network wirelessly.  This will be self-powered for maintenance-free operation.

3 Central Hub

The focal point of the system where all "static" sensor nodes report their status.  The data is collated here then packaged before being sent to the cloud for storage.  The central hub will also dispatch any remote control commands to a connected sensor node.

4 [Vehicle] Emission Sensor

This sensor will be fitted to a car's exhaust system and then be connected to the smartphone device via Bluetooth LE.    The main component for this node will be a CO sensor which will measure the relative CO emission of the vehicle.   An accelerometer will also be fitted and will be used to detect the engine's vibration to determine whether it is running or not.  The duration for which the vehicle's engine is running multiplied by the CO emission factor will be counted towards the carbon budget.  The CO emission data can also be used to notify the user about the relative condition of the car, ie. the higher the emission as compared to a known standard, will suggest to the user that the vehicle will require some servicing.

5 Cloud Platform

This part of the system will include two sub-components: data storage and data viewer.  The central hub and the smartphone will send sensor node data to the cloud storage part.  The data viewer will basically be a web application that will retrieve information from the cloud storage and will graphically present the information on a web browser.  Given the separation of the data [model] with the view, this architecture would make it possible to have a separate view running on a smartphone.

The system has a lot of connected sensors and I have explicitly not went into the details of the components to be used since all these are still up in the air atm, although the initial thoughts would be to use:

  - CC3200 as the main processor for both the indoor and outdoor sensor nodes.

- MSP430 as the main processor for the Vehicle Emission sensor

- Beagle Bone Black (AM335x) for the central hub

- ACS712 for current sensor

- MQ-135 + MQ-7 air quality sensor

- HTU-21D digital temperature and humidity sensor