Abstract Reverse Engineering of a Household Fan UEET101 Section 1 Group 1 Final Proposal Draft Justin Abraham Jonathan Abramson Matt Allen Byron Anderson Daniel Baffin Matt Waterman (Group Leader) Group 1 dissects and analyzes a typical, modern household fan to determine how electrical, mechanical, and industrial engineering methods apply to the design, construction, and every day function of the product. The fan's construction is reverseengineered in order to gain insights into how it was constructed and how it might be improved. Chapter 1 - Introduction The typical fan found in homes today is likely to be much more complex than fans of the past. Low cost microcontrollers and manufacturing techniques has led to significant innovation in products that might not have changed significantly for decades. The Holmes fan analyzed by Group 1 has many novel features that easily demonstrate aspects of mechanical, electrical, and industrial engineering. Priced at approximately $50, the fan is considerably more expensive than traditional fans, but this cost is a reflection of the fan's features. The fan is modern, lightweight, compact, and includes many useful features such as a sleep timer, oscillator, three speeds, and a remote control. Since it comes with a three-year warranty, the fan must be constructed to be reliable enough to last longer than three years in order to reduce the cost spent on repairing or replacing defective fans. Chapter 2 - Mechanical Engineering There are several mechanical components at work on this fan, the first being the motors. The main motor is located on the rear of the unit and drives a shaft, turning the actual fan blades. A second, smaller motor, powers the unique oscillation device. Both motors mount to portions of the fan's frame that must be stiff enough to withstand the torque. Gears in the the motor assembly for the oscillation device allow the device to spin slowly and consistently
with the small motor. The motors are the heaviest components of the fan and are mounted towards the center of the fan's height. The fan must be constructed such that the weight is balanced so the fan will not tip over during normal use. Portions of the base of the fan sweep backward to provide added stability. Not only did mechanical engineers ensure that the enclosure is well-balanced, they also designed an attractive and very functional enclosure. For instance, if the fan does tip over onto the rear, the enclosure is constructed such that airflow will not be restricted enough to prevent air from flowing through the fan and cooling the motor. This same aspect of the design allows the fan to be placed closer to walls and other objects than traditional fans. The efficiency of the mechanical parts is important. A mechanical engineer should calculate what degree the fan blades should be to maximize movement of air and minimize noise at speeds that will be useful to the consumer. Complex analysis of the fluid dynamics of air through the fan may have been performed during the design of the fan to optimize airflow. The motors must be powerful enough to move the blades and the oscillator for the life of the fan. The oscillator on the front of the fan also serves as a grill to prevent objects from hitting the fan blades and must be constructed to be strong enough for this task. Quality is very important when designing products and the mechanical components of the fan must be designed to last through the life of the fan and will require little or no maintenance. Chapter 3 - Electrical Engineering Aspects Electrical engineering is perhaps the most obvious area where this particular fan stands apart from the more common models. Instead of having only a switch that, at best, controls several speed levels, the electrical operations of the fan are managed by a microcontroller. Several buttons on the front of the fan and on the remote provide user input to the microcontroller and several LEDs and a piezo beeper provide feedback. Many of the fan's unique features rely on the mictrocontroller, including the sleep timer, breeze modes, speed control, oscillation, and the ability to decode digital signals sent via the infra-red remote control. The fan is powered by 120v AC current and is rated to draw 0.4 amps. It has an internal circuit breaker for added safety in the event that the fan malfunctions and draws too much current. A single printed circuit board contains all of the circuitry, including a small transformer to power the electronics. The large AC motor spins the fan blade element at one of three speeds. Depending on the breeze mode, the motor will either spin constantly at a selected speed or, if a breeze mode is selected, the fan will alternate between higher and lower speeds automatically to approximate a
natural breeze. The second, smaller AC motor spins in either direction at a single speed to turn an array of fins on the front of the fan which cause air to flow in varying directions as it rotates. The main source of current draw is from the main motor of the fan. When plugged in, the fan will draw a minimal amount of power in order to run the microcontroller in standby mode. This allows for the fan to be powered on by pressing a button on the front or via remote control. The 120v AC motor that powers the oscillator is rated to draw no more than 0.036 amps and so represents a minimal impact on the total current drawn. The LED indicators on the front of the fan use negligible power. The total amount of current used will vary widely depending on whether or not the oscillator is in use and, in particular, which speeds or breeze modes are selected. When operated at the second power level (out of three) with the oscillator rotating clockwise and no breeze mode selected, the fan was measured to draw approximately 0.28 amps. This is significantly less than the rated 0.4 amps and is probably more typical of the fan in average use. Chapter 4 - Industrial Engineering Careful implementation of industrial engineering practices is necessary in order to make the fan competitively priced and reliable. In order to minimize cost, the fan is constructed almost entirely of plastic. The separate pieces are assembled easily, making for a fairly cheap product that is durable, easy to use, and marketable. The motor assembly that powers the oscillation device includes gears already built into the stamped-metal housing of the assembly. This component is dropped into place and secured with screws. Altogether, the fan only uses three separate sizes of screws. Further simplifying the assembly process, most of the electrical connections are made with crimp connectors. The wires connecting the PCB to the main motor are the only connections that must be soldered during the final assembly. The total cost of the individual components and assembly of the fan is estimated to be less than $20. Due to its innovative features and construction, the design of the fan is likely to have been uncharacteristically intensive. The shape of the fan's complex enclosure would have required the use of 3D computer aided drafting and may have involved significant artistic consultation. The effective and quiet operation of the fan blades indicates that costly computer-based analysis of fluid dynamics through the fan might have been performed. Furthermore, the microcontroller which the fan relies upon so heavily for its features would have required microcontroller programmers to create the software in use. The fan's remote control is likely an off-the-shelf model provided by a third party at minimal cost.
There are too many variables involved in calculating the profit margin of the fan to be determined through reverse-engineering. Other variables beyond those mentioned above include the packaging, cost of shipping to retailers, the costs of the retail process in general, and many others. The manufacturer must also me mindful of the potential costs of warranty work for fans that malfunction within the three-year warranty period. All of these factors and the total number of fans sold contribute to the profitability of the $50 fan. Chapter 5 - Environmental Impact Calculating the environmental impact of the fan involves many potential variables. Holmes does not indicate that the fan has been constructed of recycled materials. The significant use of plastic in the fan means that a considerable amount of petroleum is consumed in order to produce the fan. Reviews posted on Amazon.com by individuals who have purchased this fan indicate that it may not be very reliable. Since most consumers do not recycle this type of appliance, it is likely that these fans will, since they will likely fail within three years, contribute to landfill waste. Their plastic and metal construction means that the fans will not decompose. On top of this, the fan requires electricity to operate. Due to the nature of electrical power generation in the United States, this means that the fan will contribute to the production of greenhouse gases. For example, based on statistics provided for electrical power generation in the state of Illinois, if the fan is used four hours a day and 180 days in a year and draws its maximum current rating, it will contribute about 20kg of carbon dioxide, 307 grams of nitrous oxide, and 140 grams of methane yearly. However, this impact is not atypical of this type of product and is largely unavoidable. Conclusion The Holmes fan is an exciting piece of technology that uses modern technology to improve on an old design. Careful electrical, mechanical, and industrial engineering create a product that satisfies the requirements of most customers in a package that is producible and profitable. Still, the fan could stand to be improved. In order to reduce the environmental impact, the fan could be produced out of recycled materials. While the fan is quiet, it could be made even quieter by increasing the diamter of the fan blades. The breeze modes have been found to be particularly useless since the fan can spin at only three speeds and the breeze modes switch quickly between them. If the fan was redesigned to provide infinite speeds, the breeze modes could be made more desirable. The sleep
timer, while it is very useful, is difficult to set since the timer must be selected using one button to scroll through the available countdown times. A second button could be added to scroll backwards through the times or the timer could be redigned to incorporate seven-segment LED displays and digital selection for custom countdown times. These improvements, however, could potentially add to the cost of producing the fan. With an already relatively high price tag, this would likely reduce sales. The reverseengineering has shown the fan to be designed and constructed very intelligently and with minimal room for improvement. References Homing In On Fan-Noise Sources In Induction Motors http://www.appliancedesign.com/cda/archives/9579942bf4938010v gnvcm100000f932a8c0 A Calculated Loss: How to Reduce Your Global Warming Emissions http://www.thegreenguide.com/doc/119/calculator Voluntary Reporting of Greenhouse Gases Program http://eia.doe.gov/oiaf/1605/ee-factors.html Amazon.com - Holmes-HAPF622R-Blizzard-Remote-Control http://www.amazon.com/holmes-hapf622r-blizzard-remote- Control/dp/B0001851B4/ref=pd_bbs_sr_1?ie=UTF8&s=homegarden&qid=1196386591&sr=8-1