THERMOSTAT

OVERVIEW

This is a cooperate project (2014) between Tsinghua Human Factor Lab and an international company. My team had 3 students and a supervisor. Each of us three needed to design a thermostat on different focuses.

EXPLORE THE PROBLEM SPACE

Through researching on published papers and patents, we identified following trends in thermostats:

Voice Control

Although there are problems in privacy and recongnition, voice control is still a promising area.

Large LCD Screen

Modern thermostats tend to adopt large LCD and digital buttons to display more complex information.

Zonal Control

Zonal control could provide users more customizable and energy efficient solution.

Price Signals

Providing price signals could help users to have a intuitive grasp of how much energy they consumed.

Remote Control

Since the house need a time to be tempered up/down, users want to remotely operate the thermostat before home.

Multiple Inputs

Users' feeling of temperature is not solely determined by the temperature, but also teh sunshine and humidity.

Integration

Thermostat could be integrated with other home appliances to provide cohesive experience.

Later, we analyzed two leading thermostat brands: Honeywell and nest.

Nest Thermostat

Nest is controlled by rotating and press outer layers. We also researched its functionality:

  • Auto-schedule
  • Auto-away
  • Report Generation
  • Remote Control
  • Sunblock
  • Time to Temp
  • Airwave
  • Auto-tune
  • Cool to Dry

Lyric is controlled by rotating outer layers, press on the two buttons in the front face of it and a small touch screen. It has functionalities including:

  • Auto-away
  • Smart Cues
  • Remote Control
  • Motion Sense
  • Short-cut Setting
  • Fine Tune
Nest Thermostat

To identify the facts and trends in China, we also analyzed famous brands inside China. From the chart below, we could see that Chinese brands really values the air quality function.

Functions of Chinese air conditioner brands

DEFINE FUNCTIONS

Firstly, we want to define what functions our design should cover.

Through comparing Chinese thermostats with Nest and Lyric, we found chinese thermostat fails in providing smart control/ schedule and energy/ spent saving functions. While they provide some key functions to Chinese customers, such as air quality monitering. We assume our product need to cover these functions. To validate our assumation, we send out questionnaires.

We made qustionnairs through SurveyMonkey covering over 50 questions. Analyzing the results of our 72 questionaires, we found the following results:

Smart Control & Schedule

According to our questionnaire, most informants have regular air-conditioner using habit, which making “smart control/ schedule” possible.

Energy Saving

This function is preferred by many informants. As our target user usually owns large house, the saving would be a large amount of money.

Air Quality Monitoring

Due to the polution in big cities of China, this function acts as an edge for the fierce competance among similar products.

We need to cover functions, including smart control, schedule, energy saving and air quality in our design.

DEFINE THE INPUT & OUTPUT

As for input and output, we showed our informants six different types of thermostats, as showing in following pictures and ask them to sequence them according to their preference.

Nest Thermostat
Nest Thermostat
Nest Thermostat
Nest Thermostat

Here is the interpreted results:

Input Preference: (1) Informants likes to use knob to control temperature. (2) Informants dose not feel confident in controlling thermostat by directly expressing feelings. (3) Touch screen is welcomed.

Output Preference: (1) They prefer larger screen. (2) Their feeling towards graphic data visualization polarized.

PROTOTYPE

Considering most respondents prefer round-shape traditional-thermostat-like design (knob control) and large screen, we would adopt design like Honeywell lyric, and Nest, while making screen larger.

To make APP coherent with controller on wall, the main page of APP would be designed like the main UI page of controller on wall.

Nest Thermostat

Schedule Mode

Users can use the on-wall controller to control the temperatures and switch between “schedule” and “event”.

Every temperature choice they made will be stored and used to alter the schedule smartly.

Event Mode

To interrupt smart schedule to prepare for event at an unexpected time, users just a simple tap to change the mode to “event mode”.

Users can set different behavior for different events on mobile App and switch between events either through App or on-wall controller.

Nest Thermostat
Nest Thermostat
USER TESTING

We had 50 subjects in our user tests. 25 of them were Chinese, and 25 of them were international students. Each of the subjects needed to finish three set of questionnaires and finish tasks on five controllers. We videoed the whole task performing process.

Nest Thermostat
DATA ANALYSIS

The data to be analyzed mainly come from video data and three sets of questionnaires. We have three indicators and six variables listed as below:

- 3 Indicators -

Workload

We had three sub-indicators of workload represented in task performance video: path length, times of confusing and task completion time.

Satisfactory

We had four sub-indicators for satisfactory: the perceived usefulness, easy to use, the attitude towards using, and the willingness to use it again.

Preference

We analyzed participants' preference through asking them to rate each design in post-session questionnaires. Then we separated the result as Chinese users and non-chinese users.

- 6 Variables -

Types of Design

Including my design, we had 5 different designs in total. My design is shown as design 3.

Platforms

One design is on tablet, others are on mobile phones.

Automation

It is convenient to have some automation, but too much might affect the sense of control.

Participants' Nationality

Our design is for Chinese users, but it is good to know the commonality and difference on different nationalities.

Expertise on Smart Thermostats

Smart thermostats are programmable, and our design involves that a lot. Thus, past experience might affect performance.

Frequency of App Control

Similarily, as our design is all about App control, we need to figure out how participants' past experience would affect.

WORKLOAD

We had three sub-indicators of workload represented in task performance video: path length, times of confusing and task completion time.

  • Significance Analysis: #1 Type of design, #3 Automation Level, #4 Nationality is significant.
  • #1 Type of design: My design requires the second most workload. (2/5)
  • #3 Automation Level: The higher automation level, the higher workload.
  • #4 Nationality: Chinese users reported least workload and European users reported the highest workload.

Explain of Result: My design offered a lot of functions, which increased the workload. We also analysed the workload of my design on individual task:

According to NASA-TLX Scale, we divided the workload represented through questionnaire in six dimensions: Mental Demand, Physical Demand, Temporal Demand, Performance, Effort, and Frustration. To calculate the total points for every design solution, we asked subjects their attitudes on how much each dimensions mean to them, and we used that as a weight to calculate the total points. Use that as the dependent variable, area and types of design solution as factors, we drew a interactions plot as showing below:

Average Workload

Takeaway: From the plot we could see the workloads reported by Chinese users (black line) on were the lowest on almost every single design solutions. The tolerance of Chinese users are high, which shows a big chance and call to design for them.

SATISFACTORY

We had four sub-indicators for satisfactory: the perceived usefulness, easy to use, the attitude towards using, and the willingness to use it again.

My design rated 1/5 in perceived usefulness, 3/5 in easy to use, 2/5 in attitude towards using, and 2/5 in willingness to use it again in Chinese participants.

Nest Thermostat
Nest Thermostat
Nest Thermostat
Nest Thermostat

Takeaway:When we drew the graphs out. We found people from different areas have different feelings towards different designs, but people from other countries in Southeast Asia (red line in plot) reported similar feelings as Chinese users (black line in plot). Thus, if we designed a thermostat for Chinese users, hopefully, we could also promote this product in other countries of Southeast Asia.

PREFERENCE

We collected Chinese and Non-Chinese’s preference towards different designs.

Explain of Result: From the Pie Chart we could tell, the most favorite product by Chinese subjects is my design. It shows the similar result as in Satisfactory analysis.

Although design three does not perform best in “least favorite by Chinese” or any result in non-Chinese, the results in these three parts are acceptable. We were not designing a product to satisfy everyone. We just need to make sure a promising part of our target user will pick our product their favorite product.