Making an IoT product to sense your work environments — DeskElf: Indoor environment quality sensing & Pomodoro Technique application
DeskElf is my individual project for CASA0016 — Making, Designing, Building, Connected Sensor Systems, one of the courses in MSc Connected Environments from the Centre for Advanced Spatial Analysis (CASA), The Bartlett, UCL. My experience has positioned me at the intersection of the IoT solution, cloud technology and business analytics and my aim is to apply my specialist knowledge to the digital twin solutions in the smart city industry.
I. Background
With the blend work model prevailing, office workers spend most of their time inside the buildings as they did before — but now stay in their homes more than offices. It is proved that indoor environmental quality has a significant influence on staffs’ productivity, health and wellbeing (U.S. Green Building Council, 2014). Unlike commercial buildings, most of the residential buildings have a lack of large-scale IT infrastructures and building-wise environmental controls which makes them hard to deploy state-of-the-art sensors in the buildings (Graham Coulby et al., 2020).
However, this problem provides a great opportunity to develop a lightweight and portable indoor environmental sensor for people who adopt a flexible working model. DeskElf is born for this need and manages to offer a desktop device helping workers keep productive and healthy at the same time. Besides, DeskElf can serve as an extended service of corporates’ wellbeing programmes, taking care of employees’ working environment just like what they do at the office.
II. Functionality
DeskElf has two major functions including indoor environmental quality sensing and the Pomodoro Technique. Regarding indoor environmental quality, DeskElf can collect live data about air quality (eCO2 and TVOC), visual comfort (light temperature and light intensity) and thermal comfort (temperature and humidity) which directly and indirectly influence productivity and health of employees (Desining Buildings, 2021).
As for Pomodoro Technique, DeskElf will remind users to take a break when the periodic working time is up. Pomodoro Technique is a time management method that breaks work time into 25-minute chunks separated by five-minute breaks (Kat Boogaard). With the help of a timer, workers can better deal with distractions and interruptions, fight procrastination, make sure they get enough rest time and, in the end, improve overall work performance (John Rampton, 2020).
III. Building Process
The step-by-step walkthrough can be found on the GitHub page here. (https://github.com/VivianKuKu/CASA0016_DeskElf_Making-Designing-Building-Connected-Sensor-Systems)To make DeskElf portable and to keep it flexible for data application, the data captured by sensors will be sent to the network server — The Things Network via LoRa gateway. So, The Things Uno board is used, and it is designed based on the Arduino Leonardo board with a microchip LoRa module (RN2483).
The building process of DeskElf consists of 4 stages from hardware setup, Arduino IDE code, The Things Network setup and the enclosure design and 3d printing.
1. Hardware Setup
The reason for choosing The Things Uno (Arduino Leonardo) board is due to the data communication concern. Since DeskElf should work functionally wherever users work, its function must be low-power consumption and long-range coverage to reduce users’ hassle in charging and reconnecting. Therefore, the LoRa network, which can deliver a 2 to 3 km-wide coverage from its gateways in the urban area, becomes a feasible choice.
For indoor environmental quality sensing, LCD is used to display real-time readings of each sensor which allows users to get updated information and take immediate action if they want. Besides, SGP30 and TCS34725 both are connected to The Things Uno board through I2C communication by occupying the SCL/SDA set and pins 2 and 3.
For Pomodoro Technique, the LDR will trigger the countdown timer function when users start working (In this case: Users will plug the FOCUS signage on the lid, changing the amount of light that LDR receives) and the LED will remind users that the working time is up, and it is time to take a break. All components are wired up as below schematic.
2. Arduino IDE code
Coding in Arduino IDE is an iterative process that requires several step-by-step testing to ensure the hardware, functions and libraries all work as estimated.
To use these sensors and actuators, multiple libraries are needed. Besides, there are six values about indoor environmental quality required to be shown on the LCD, so the automatic screen-scrolling effect is designed by coding.
Regarding the Pomodoro Technique, instead of using the delay function that will block other codes, the Timer library is adopted to support calling functions in/at/every specified unit of time (Michael Contreras, 2022). Here, the code will call an alert function every 25 minutes whenever the analogue reading of LDR is below 100 caused by the coverage of FOCUS signage. And the alert function will make LED start blinking 5 times.
As for The Things Uno board, Serial is reserved for USB CDC communication, while Serial 1 is used for communicating via TTL serial on pin 0 (RX) and pin 1 (TX) which allows communication between The Things Uno and the microchip LoRa module (Arduino). Also, it is important to get the information of the board such as DevEUI (a unique identifier assigned by manufacturer) and AppEUI (a global application ID) in the beginning. And since the bandwidth is a fixed resource that is shared by many devices and there is a limited airtime (LoRa-Developers, 2021), it is necessary to minimize the size of the payload by converting sensor values to unsigned integers — uint16_t — which contains 16 bits for a word. In the end, ttn.sendBytes() is used to send messages with an array of bytes and their size (The Things Network, 2021d).
3. The Things Network Setup
The Things Network (TTN) is a global, open, and crowd-sourced initiative to create an Internet of Things data network over LoRaWAN technology. To send sensor data to TTN, one of the most important things is to check the coverage of the LoRa gateway in the TTN Mapper (The Things Network, 2021c) or to consider deploying a gateway by yourself. Once creating a TTN account, a new application should be created, and the device must be registered for the application. Besides, users should obtain the Frequency Plan according to the location of devices, as an example, EU863–870 is used in the United Kingdom. The step-by-step walkthrough can be found on the TTN website (The Things Network, 2021b).
What’s more, users should keep an eye on the limitation of The Things Network. Not only make the size of the payload as small as possible but also adjust the transmitting interval and the data rate if necessary (The Things Network, 2021a). However, DeskElf doesn’t go further to explore the best interval between messages, and it will transmit data every 12 seconds for now. Finally, the following code is used to decode the messages from the node.
4. Enclosure Design and 3D Printing
The enclosure of DeskElf contains three parts — signage, lid and base. The signage allows users to plug in when they start to work, and it will cover the LDR beneath the lid and change the analogue reading of LDR and ultimately trigger the countdown timer function. The lid is used to hold signage, light sensor (TCS34725) and LED. And the base is designed to accommodate The Things Uno board, breadboard and other components with some holes on the walls to keep the circulation of air. The enclosure is designed on Fusion360 and printed by the Prusa 3D printer. The 3D printing files can be found on the GitHub page.
Reference
Arduino (no date) Arduino — Serial. Available at: https://www.arduino.cc/en/reference/serial> (Accessed: 15 December 2021).Desining Buildings (2021) Indoor environmental quality. https://www.designingbuildings.co.uk. Available at: https://www.designingbuildings.co.uk/wiki/Indoor_environmental_quality (Accessed: 3 January 2022).Graham Coulby et al. (2020) ‘A Scoping Review of Technological Approaches to Environmental Monitoring’, International Journal of Environmental Research and Public Health, (International Journal of Environmental Research and Public Health), p. 25.John Rampton (2020) The Benefits of the Pomodoro Technique, The Benefits of the Pomodoro Technique. Available at: https://www.calendar.com/blog/the-benefits-of-the-pomodoro-technique/ (Accessed: 29 December 2021).Kat Boogaard (no date) The Pomodoro Technique Really Works for Productivity | The Muse. Available at: https://www.themuse.com/advice/take-it-from-someone-who-hates-productivity-hacksthe-pomodoro-technique-actually-works (Accessed: 1 January 2022).LoRa-Developers (2021) LoRa best practices Packet Optimisation Introduction | DEVELOPER PORTAL. Available at: https://lora-developers.semtech.com/documentation/tech-papers-and-guides/the-book/intr/ (Accessed: 29 December 2021).Michael Contreras, M. (2022) arduino-timer — library for delaying function calls. Available at: https://github.com/contrem/arduino-timer (Accessed: 1 January 2022).The Things Network (2021a) Limitations, The Things Network. Available at: https://www.thethingsnetwork.org/docs/lorawan/limitations/ (Accessed: 12 December 2021).The Things Network (2021b) Quick Start, The Things Network. Available at: https://www.thethingsnetwork.org/docs/devices/uno/quick-start/ (Accessed: 5 December 2021).The Things Network (2021c) TTN Mapper, TTN Mapper. Available at: https://ttnmapper.org/heatmap/ (Accessed: 29 December 2021).The Things Network (2021d) Working with Bytes, The Things Network. Available at: https://www.thethingsnetwork.org/docs/devices/bytes/ (Accessed: 10 December 2021).U.S. Green Building Council (2014) Green Building 101: What is indoor environmental quality? Available at: https://www.usgbc.org/articles/green-building-101-what-indoor-environmental-quality (Accessed: 3 January 2022).
