The first step is data collection, where all the data collected consist of methods that relate to this study. 24 units of existing products of carbon monoxide detectors have been benchmarked and analysed according to their features, functionality, design, size, and capabilities to know the user needs by using the market positioning, specification analysis, and position map. Product features are important to help the user to know more details, including the purpose of why the features exist in that product. The size of the product is also an advantage for the product because the usual carbon monoxide detector mostly is not lightweight. It can be hard to attach to any surface. The height and width of the product make sure that the device is handheld, compact, and easy to attach to any surface. Then, the other features, such as the LCD display, can make it easy for people to know the real time of carbon monoxide values. The battery level can also be seen due to the period of usage as shown in Figure 2. The difference between the usual carbon monoxide detector and the bulkier design is that the latter is also not as aesthetic as the handheld carbon monoxide detector because of the sensor, buzzer, and alarm at the back of the product, which is more compact. Refer Table 1 for details of features.

Furthermore, it is impossible if the sensor is not included together in the carbon monoxide detector. Also, the alarm light is an additional feature that is quite good for carbon monoxide detectors to give a signal for carbon monoxide detection. Moreover, this part is the most important thing of carbon monoxide detectors to increase the productivity of the product while giving a good appearance for the usage of the device. This part also can influence the usage of the carbon monoxide detector that is different from other carbon monoxide detectors which are not portable and lightweight. Next, the alarm light and saved max light are additional to attract the user to use that detector. By combining all these components, it can boost the functioning of the carbon monoxide detector, and it can be a user-friendly carbon monoxide detector. Lastly, the most important part of this device, which is the sensor and buzzer, must be suitable for the size and functionality.

Figure 2. Features of carbon monoxide detector.

Table 1.Details of features.

The second step consists of data collection that is already analysed by categorising the features that are suitable for user needs and can satisfy the user instead of just developing the product without using any guide. There is a questionnaire that involves the emotional aspect due to the features that are needed in a carbon monoxide detector. Kansei methods that are always related to the emotional reactions of the user according to the product, which can define user needs. Kansei engineering is a methodology that is suitable to guide the product development or improvement of products that can involve the emotional responses of customers into design elements and features of the product. This is frequently referred to as the customer’s unspoken needs or “voice”. It is inherently vital and sensitive for users or consumers; once fulfilled, it can result in great satisfaction and loyalty [13]. The words “kansei kougaku” in Japanese refer to the emotional or effective engineering due to the user experience.

Based on Figure 3, the concepts of KE refer to the feelings and emotions of the customer towards the product. The product’s quality includes visual appeal, tactile sensations, sounds, and even smells. Products describe the emotional responses or feelings that are gathered from users through surveys or interviews. The KE also involves data collection with various methods, which are surveys, interviews and observation that can be qualitative and quantitative. After collecting the data, the data will be interpreted to identify the patterns and correlations between design and emotional users. It can give analyses such as statistical and factor analyses and neural networks. By converting the data to the Kansei analysis, it can visualise the specific design elements and features that are suitable for product development. The prototypes will show the functionality or design based on the design that was collected. Moreover, the product design can ensure that the emotions of the user are achieved. This method can also facilitate easy adjustments.

Figure 3.Kansei engineering method.

Kansei Engineering is a methodology that requires human emotions toward the product and gets the collected data to analyse the design’s elements and features that are required to design a development product. It can also be used in various industries to ease the product or service. Then, KE can enhance the productivity and functionality of the product to improve its user experience.

This study provides a questionnaire survey that involved 51 respondents about their opinions on carbon monoxide detectors aligned with their preferences based on the appearance of the products. The Kansei method can be used to focus on questions related to appearance, including shape, size, and additional features. The questionnaire gathers Kansei terms that influence the user’s selection of product features. The result can be to figure out the customer requirements. The questionnaire comprises three sections: A, B, and C. Section A provides general or basic topic information such as age, gender, and occupation, and it asks the user if they have a car or not. This type of question helps to understand how people are drawn to these studies. Furthermore, the device appeals to older individuals due to its ability to safeguard their families from carbon monoxide poisoning. The results from section A’s general user information were collected to know who’s the main target of this study.

The general knowledge of users regarding carbon monoxide detectors is discussed in section B. This section can ease the process of collecting the data of user preferences, such as the appearance of the carbon monoxide detector device. There are assorted designs of carbon monoxide detectors, such as for home users and for travel users, by prioritisation of the emotion of a carbon monoxide detector. The user also will ask about the preference of the factor to buy the carbon monoxide detector due to its functionality and appearance. Refer to Table 2 and Table 3 for the summary from the survey.

Table 2.Summary of section A (demographic).

Table 3.Summary of section B (general knowledge).

Finally, the user in section C must choose the Kansei words. It can describe the feeling or emotional user towards the carbon monoxide detector suitable with the Kansei method [13]. The result of the survey is summarised in Table 4. According to the survey results, it can gather all the information that can be helpful in the development process. Thus, the questionnaire surveys can include every kind of person with diverse kinds of opinion.

Table 4.Summary of section C (user preferences).

The third step is the product development process. The design element and finding of the research can be visualised in the real product with the development of the prototyping. Design development is developing innovative ideas to build the product based on their system and design [14][15]. By focusing on the functionality, usability, aesthetics, and feasibility in detailing the product. In this topic, the preliminary design to create the initial sketches of the product and using the 3D models to define the product functionality. It also involves the material that is used in this product. Detailed design which involves precise measurements due to the initial sketches. It can also include the material specification and technical details, such as the CAD models, circuit diagrams, and systems that are used in the product. In this study, circuit diagrams are the most important to this study to test and validate this study.

An investigative sketch is the sketch that can create the visual of the product that can represent the idea and problem-solving phases. It also can guide the development process because the sketch includes the features, design, and functionality of carbon monoxide detectors. By exploring the design and functionality of carbon monoxide detectors that are able to suit this study. The multiple shapes can give an idea to improve the design to be more aesthetic and user-friendly interface. Explanatory sketches of the design ideas before creating the finalised sketch. It must be simple to help with brainstorming and visualising design ideas. By planning the layout of products that is done by the designer. This stage is most important to plan what kind of shape and design that suits this study. It can also guide the development of more designs.

Below is the explanatory sketch from the brainstorming ideas as shown in Figure 4. Explanatory Sketch 1 has an uncomplicated design with an oval shape that fits the component inside. The width and height are suitable for prototyping. Additionally, this design incorporates an attachment suitable for mounting on a car dashboard. The holes for this shape are due to sound alerts and LEDs for carbon monoxide detection at a high level. The LCD also serves as a monitoring tool. Explanatory Sketch 2 has a unique shape that distinguishes it from other sketches. The component can also fit perfectly due to this design. The height and width are also perfect for the prototype of the carbon monoxide detector. The LCD is required to monitor; the

1 2

3

Figure 4.Explanatory sketch 1, 2 and 3.

level will be shown at the display. Also, for this design, the LED will trigger when the carbon monoxide is at a high level. Attachment is important due to the car dashboard. Explanatory Sketch 3 has a minimal design and aesthetic design that can fit the component with a suitable width and height. It has holes that can provide sound detection of high carbon monoxide. Including the LCD is important due to the carbon monoxide level display and attachment purpose. The LED is also the same as the other design in that it triggers the high carbon monoxide level.

To select the final design, use the Pugh Matrix method to define the perfect design for this study. Pugh Matrix is a type of matrix design that can guide comparison of designs. The best design will be selected based on the established criteria. Analysing using the best weight based on the section C in Table 4, percentage from the questionnaire would be as follows. In this Pugh Matrix as shown in Table 6, it can categorise the weightage into five categories as illustrated in Table 5. Score 5 is the feature that more than 50% of users in Section C’s survey results preferred. Then, scores of 4 and 3 are given to the features that are more than 45% to 50% and more than 40% to 45% of the preferred features by the users, respectively. Lastly, score 2 and score 1 are the percentages more than 35% to 40% and more than 30% to 35%, respectively, preferred features in section C. The score each feature by selecting a suitable design for the carbon monoxide detector. By using the score and weight, the final score for each sketch can be identified.

Table 5.Pugh matrix weight.

Sketch 3 was chosen due to the shape rarely used for carbon monoxide detectors. Also, the design has smooth, rounded edges for both safety and aesthetic reasons. It indicates that the equipment is intended to be portable or user-friendly. Inside the component space, all the sensors and components are indicated in rectangular space. A rectangular cut-out on one side identified as an LCD. This panel may display readings, settings, or notifications. On the side, little holes have been sketched for ventilation or sound output. This shows that the gadget may incorporate airflow-dependent components such as a buzzer, microcontroller, or sensor. A smaller labelled portion beneath the LCD suggests an attachment point for mounting the gadget on a surface or integrating it with other devices. The small profile and general design make it ideal for handheld or portable applications, emphasising both functionality and ease of use.

Table 6.Pugh matrix.

3D CAD can create the detailing of a product and precise product design by conducting the exact measurement and detailing of product design as shown in Figure 5. It involves the design that is selected from the explanatory sketch and also can apply the material that is suitable for product design. It can illustrate the details of the design of the preliminary sketch. Also, drawing can include the multiple views, which are front, side, top and isometric views. By using SolidWorks software to create the 3D model, you can view the design from the top, front, and side perspectives as follows. The dimension of this top is 120 × 120 × 22.50. This kind of shape is suitable for prototypes and includes 5 small pins that can attach easily with the bottom. The bottom dimension of the prototype is 120 mm × 140.01 mm × 22.50 mm. This kind of shape is suitable to place the component. It also has holes to give the sound of a buzzer when carbon monoxide is at a high level. The functional and ventilation elements also are shown to describe an ergonomic and visually appealing shape. By maintaining a lightweight design, the wall of this product is thin, not like the other parts. The isometric view also helps to provide a 3D perspective that can visualise the final product as shown in Figure 6. The design appears practical and functional for component placement, which has proper accessibility for user interfaces.

Figure 5.Drawing of the final design.

Figure 6.Views of the prototype.

3D printing allows for the creation of component casings according to the selected design. The two parts consist of completing the casing for the components. Plastic 3D printing usually uses material such as PLA (Polylactic Acid) or ABS (Acrylonitrile Butadiene Styrene), and it depends on which is suitable for printing. The finishing of the surface also has visible layer lines because of the typical quality of material. This 3D-printed enclosure is consistent with the previous sketch, implying that it is part of a prototype for an electronic device, such as a sensor or monitor. It works and shows how 3D printing can be used to make custom enclosures for electronics as shown in Figure 7. To develop the functional prototype, it will include the entire process to assess the design in the real world and identify the performance of product limitations. From this, it can know the efficiency of the product itself while maintaining the functionality and quality of the product. This area also allows for management of the product’s capabilities.

Figure 7.3D Printing of the prototype.

Finally, step 4 is testing and validation of the product that collected the feedback from users about the product, such as the functionality of the product and the design of the product being suitable for the market. The refinement product needed to improve the process by using the Kansei Engineering (KE) and User Center Design (UCD) methods combined to get the product that follows the user needs. By using the UCD method, it can guide the prototype according to the functionality of the product, which can be an important aspect due to the carbon monoxide detector that consists of the user characteristics and priorities that can be included in this study. It also contributes the user preference that can assess the product to collect feedback that can be an optimal way for usability tests. The UCD methodology as shown in Figure 8 is the process create the product based on the preferences and limitations of the end user, which is to give the design and development of the process easily to process. UCD also is the sustainment, which is a process of rebuilding the world and humanity to generate new opportunities for environmental sustainability and ensure the product is high quality and satisfies the functionality of the product [16]. This method also can be used to involve the product through the design and feedback of the product. It can also assist in the product development process by identifying the needs, limitations, and preferences of the end user. The aim of this method is to conduct testing and refinement based on the product’s requirements [17].

There are benefits which are the usability of products improved by leading to higher adoption rates and user satisfaction. Every product must match the suitable features that can fulfil the user satisfaction. User feedback can enhance the product to meet user needs and expectations, ultimately leading to user satisfaction. Also, the design process can save time and resources by identifying and addressing usability issues to reduce the development cost. The challenges of the UCD method required the method with time-consuming conduct of the testing and research that was required due to the project development. Then, the developer will face the technical constraint and business goal to balance the stakeholder needs. Other challenges include the evolving preferences and needs of users, which can change over time and require updates and ongoing research in design development. The UCD method can ensure that the product will be designed according to the end user preference to be a more functional and useful product following the user preference. Understanding user emotions and experiences, such as those studied in Kansei Engineering (KE), is also important for knowing the design process.

Figure 8.UCD process.