User-Centric Development and Evaluation of a Thermal Control Device for Office Use
Master’s Thesis | Solo work | UI Development and Usability Study
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Overview
For my master’s thesis, I designed and developed a prototype thermal control device aimed at optimizing temperature settings in shared office spaces. The project focused on creating a user-centric interface for controlling HVAC systems, addressing the challenge of maintaining comfortable temperatures amidst frequent occupancy changes. The core idea of the device is to allow users to provide feedback on their comfort levels using cost-effective electronics, rather than relying on expensive hardware to detect and analyze their thermal comfort.
Abstract
Thermal comfort is an important factor for human performance and health. It is influenced by environmental conditions, individual metabolism, and clothing. Studies have found that individuals' optimal temperatures can vary significantly. An environment that is too cool or warm can stress the body, impairing cognitive function as the body strives to cope with uncomfortable conditions. Therefore, thermal conditions should be adjusted for individuals. While programmable thermostats are common nowadays, they have been found lacking from the user's perspective. Understanding the interfaces of programmable thermostats can be challenging, leading to poor thermal comfort. Hence, it is crucial to develop a temperature control system that considers individual needs and is designed with a user-centric approach.
For individual temperature regulation, it is crucial to understand what temperature would be suitable for an individual and adjust the room temperature accordingly. Smart thermostats and various sensors enable personalized adaptation of room temperature. Additionally, for usability purposes, it is important to provide users with the option to manually adjust the room temperature. A personalized approach promotes overall thermal comfort and supports the well-being of individuals.
In shared office spaces with frequent people flow, adjusting the optimal temperature for individuals is particularly challenging. The first objective of this thesis was to design and develop a prototype device for personal thermal control in an office building, taking into account the needs of the personnel. This was achieved by utilizing usability expert methods such as sketching, prototyping, heuristic evaluation, and hierarchical task analysis. These methods provided guidelines for developing a user-centric interface. The second objective was to assess the usability and suitability of the developed temperature control prototype device for indoor temperature management. Seven participants took part in this study conducted at Aalto University.
The user and usability research consisted of three main phases. In the initial phase, interviews were conducted to get to know the participants and their knowledge of current heating systems. Additionally, they performed a thinking aloud task which was used to evaluate their user experience and identify interface problems. For the second phase, each participant was provided with the prototype device, and they visited the research room three times to accumulate prolonged usage experience. This was necessary because adjusting room temperature is a slow process, leading to slow feedback for users. In the final phase, participants' experiences and thoughts on the prototype device were gathered through interviews. Finally, they were asked to complete a questionnaire, and the results provided insights into the overall usability of the device.
This study confirmed previous observations regarding people's needs to control room temperature and provided insights into the future development directions of the personalized temperature control device developed in the study. Most participants found the developed temperature control method interesting, good, and useful. However, they expressed a desire for additional features before considering it suitable for the office environment. The results can be valuable for future developments of personalized indoor environmental control systems.
My Role
Designed and developed the prototype device and user interface.
Conducted sketching, prototyping, heuristic evaluation, and hierarchical task analysis.
Performed usability testing with real users across three phases.
Analyzed feedback and provided recommendations for future development.
Problem
Comfortable temperature is crucial for human performance and health, especially in shared office environments where varying occupancy makes it difficult to maintain optimal settings for everyone. Using sensors to assess individual thermal comfort in office buildings can be quite costly.
Solution
I developed a prototype device that enables users to provide temperature feedback directly to the HVAC system. The development process involved designing the initial interface through sketching and prototyping, conducting heuristic evaluations, and performing task analyses. Usability testing with real users was then conducted to further refine the interface.
Process
1. Design & Development
Sketching: Initial interface concepts were sketched to visualize potential designs.
Prototyping: Developed a working prototype of the thermal control device.
Heuristic Evaluation: Assessed the interface to identify usability issues.
Hierarchical Task Analysis: Analyzed tasks to ensure intuitive user interactions.
2. Usability Testing
The usability research consisted of three main phases:
Initial Phase
Interviews: Conducted to understand participants’ knowledge of current heating systems.
Think-Aloud Task: Participants verbalized their thoughts while using the prototype to identify interface problems.
Prolonged Usage Phase
Device Usage: Participants used the prototype in a research room over three visits to experience prolonged usage. This phase was crucial due to the slow feedback nature of temperature adjustments.
Final Phase
Interviews: Gathered participants’ experiences and thoughts on the prototype.
SUS Questionnaire: Participants completed the System Usability Scale (SUS) to provide quantitative data on the device’s usability.
Tools Used
Arduino
Esp32
Shapr3D
EasyEDA
Node-RED
Raspberry pi 4
JavaScript
3D printer
Outcome
The study confirmed previous observations regarding people's need for personalized temperature control in shared office environments and provided insights for future development of such devices. Participants found the control method interesting and useful, although they desired additional features for it to be fully suitable for office use.
Key Results:
Identified essential usability issues and areas for improvement.
Provided actionable insights for the future development of personalized temperature control systems.
Confirmed the importance of user-centric design in environmental control systems.
Visuals
Figure 1: The developed prototype device.
Figure 2: One view of the devices interface.
Figure 3: Top view of the PCB, featuring an OLED display and three push buttons, showcasing the interactive interface.
Figure 4: Bottom view of the PCB, displaying the copper traces, solder joints, and attached components, including the Seeed Studio microcontroller (XIAO-ESP32-C3).
Reflection
This project underscored the importance of user-centric design and iterative testing in developing effective control systems. The comprehensive usability testing approach ensured that user feedback was thoroughly integrated into the design, leading to valuable insights for future developments. The experience enhanced my skills in user research, prototyping, and usability evaluation.
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