Ata Basol, Ali Doganci, Benjamin Gilbert, Sayed Mohammed
Introduction
Our client brought upon us the task to design and produce an overhead light for a motion-limited person. In this report, we will be demonstrating and analyzing our approach and execution toward fulfilling this task. We initially compiled a list of meaningful objectives and metrics and then used this to create a list of necessary functions, which guided our approach to designing the product. After this, we ultimately decided to build a light that would toggle between four different modes when it detects two claps made between 0.5 seconds and 2 seconds of each other. Our device uses an Arduino Nano as the microcontroller, two LED chips for light outputs, a sound sensor module to detect the claps, and a 12V AC adapter to power the device. Once our final device was built, we tested its ability to toggle between different modes and learned that it could do so from a double clap up to 18 feet away. We also tested its lighting in different modes and learned that it provides sufficient light to illuminate an average sized room.
For a person who is bedridden or has limited motion abilities, simple tasks, such as getting up and flipping a light switch, can be a challenge. This motivated us to design and build a portable overhead light for a motion-limited person in order to allow them to control their illumination needs without additional assistance.
We aimed to create a device that followed these objectives and metrics:
Affordable - the device should cost less than $40 to manufacture
Illumination - the device should provide 1000 - 2500 lumens of light
Portable - the device should be smaller than 6” x 6” x 6”, weigh less than 5 pounds, and be mounted and unmounted on a wall or ceiling without damage
Touchless Control - the device should be controllable within 15 feet or less without touch
Provide Uniform and Non-Uniform Light - the device should have at least two light radii settings
Multiple Brightness Settings - the device should have at least three brightness settings
Safe for use - the device should conform to UL 153 & CSA C22.2 No 250.4 portable luminaire safety standards
Design Alternatives and Final Product
There were many different approaches we discussed when deciding which means and functions would optimize our design. We first constructed a morph chart to list possible means for our functions (Table 2). Next, a pairwise comparison chart was created to figure out which objectives were most important (Table 3). Based on our PCC, we decided the most important functions we would have to focus on were touchless control, illumination, and portability. After picking the best option for each functionality, we created a glass box diagram (Figure 6) to see how all the means would interact within our device. All of these steps, including the testing seen below, were taken into account when deciding our means.
Touchless Control
We initially listed out all the possible ways the device could be controlled without touching it. The most feasible options we settled on were controlling the light through sound, ambient light, or by remote. We wanted our users to be able to control the light whenever they wanted to, so we instantly ruled out ambient light. Then, we decided against using a remote to control the device since it could be difficult for someone with limited fine motor skills to work the device. We were then set on using sound to trigger the device, but had to decide what sound would control it, and what type of sound sensor would be used. We initially planned on using a voice recognition module to control the light based on certain keywords, but the module was very expensive and was not reliable to control the light consistently. It was decided that the simplest and most efficient way to control the light was through two claps, since a clap is a simple noise to make, a double clap would differentiate the trigger from unrelated noise, and sound sensor modules were relatively cheap. We tested out a condenser microphone module (LM393 Sound Sensor) and an electret microphone module (MAX4466) to see which would better pick up a clap over distance. Through this experimentation, it was clear that the condenser microphone would be the best choice, as seen in Figure 1. It was then decided that we would use the LM393 Sound Sensor module to sense a double clap in order to trigger the LED chips.
Illumination
When evaluating the illumination objective of the design, we knew we would need a high powered light to illuminate an average sized room, so we tested a 10W Cool LED Chip and a 10W Warm LED Chip. The 10W LED chips were chosen for their small size and powerful light output, which provided more portability without sacrificing power. Two parameters, the intensity/voltage ratio and the light beam angle, were tested to determine the best possible light source. The low, medium, and high voltage input values were determined to provide the most efficient three-level brightness setting. Lux meters were used to gather data and 12V were used to power the LEDs. After comparing the data and results, it was found that the 10W Cool LED Chip used less voltage while producing more intensity and provided higher intensity levels in any measured angle. Therefore, the 10W Cool LED Chip was concluded to be the most suitable light source for the project due to its small size, powerful light, cheap price, and more efficient energy consumption. The illumination needs for small rooms were met as the device provided 300-400 lux of ambient lighting when in standard modes, as seen in Figure 5, which falls into the recommended range of 200-400 lux by IESNA for such spaces.
Portability
We thought that either using acrylic or 3D printing for the housing would be our best options, but ultimately went with 3D printing. By 3D printing it using PLA plastic, we were able to make the housing be only two pieces at a very low cost as opposed to having multiple pieces of acrylic we would have to connect. The housing is small with an easily removable top using screws. The power hole is on the side so it can be out of the way of the light. Another advantage of 3D printing is that we were able to make an indented portion for the spotlight lens which would have been much more difficult to do with acrylic. The sound sensor hole is also on the bottom which allows for very easy sensing. PLA plastic is very durable and doesn’t allow any residual heat from the LEDs to be felt. It is also very light which helped us make this less than 2 pounds. We believed that either a magnet or sticky adhesive would work out well for mounting, but went with velcro command strips. It is long-lasting and can easily hold the lighting fixture. It can also be moved from place to place easily. They also won’t damage the walls at all and are easily removable.
Evaluation of Results
After analyzing our device, we determined that we met all the objectives stated in the introduction. The objective of keeping the device affordable was met, since the total cost to produce the device was $31.37, as seen in Table 1. The objective of illumination was met, as the output illumination is enough to light a whole room comfortably. The final product is portable as it is 4.5 by 4 inches and has a height of 2 inches, weighs less than 2 pounds, and can be easily mounted and removed with our velcro mount (Figure 2). Our device can be controlled by a double clap from a distance of up to 18 feet, which meets our touchless control objective. The uniform and non-uniform light and multiple brightness setting objectives are met since our device operates with three different brightness settings and has two different light radii. This was accomplished through our code (Figure 4) and the use of a lens. Finally, our device conforms to UL and CSA portable luminaire safety standards, since it meets all the necessary requirements. It has a properly rated cord, a grounded 3-prong plug, and proper labeling indicating its electrical rating, manufacturer, and model number. The wiring inside the device is secured and insulated to prevent electrical shock hazards. The housing and enclosure are made of suitable materials for durability and resistance to impact damage.
After we assembled our final product, we tested it multiple times and discovered some key findings. First, we discovered that a limitation to using the LM393 sound sensor is that it can be triggered when the device is being touched and moved around. Therefore, we recommend that the device is mounted before being plugged in. We also measured the lux output of the different light modes at three different angles of 0, 45, and 90 degrees to determine that our device can well illuminate an average-sized room, as seen in Figure 5. It also shows that at 0 degrees in the spotlight mode, the lux output is really low which means that the spotlight function illuminates ahead and not the surroundings.
Lessons Learned
While designing and producing our device, we learned a vast set of skills and lessons needed to design a successful product and work with a team. Entering this project, although we all had experience in brainstorming and modeling, we did not have experience with the proper engineering design methodology and completely building a product from the ground up. From the start, it became very clear that the most important aspect of taking on such a large project was to be organized and communicate. We soon realized that we had to assign different positions and assignments to each teammate and constantly communicate about the status of each step. Lastly, there were moments throughout this semester where aspects of our project wouldn’t seem to work or come together for days at a time. Through this, we learned that sometimes you need to take a step back and decide if you are wasting your time with one approach and are better off going back to the drawing board to look at the project from a different angle. Overall, this project was an extremely valuable learning experience that will be carried with us throughout our careers as engineers.
References
The Lighting Handbook, 10th Edition by IESNA