2 DESIGN REQUIREMENTS2.1 Technical Design Constraints2.2 Practical Design Constraints2 DESIGN REQUIREMENTS Playing a musical instrument is an enjoyable hobby shared by many people worldwide. Light Leader promotes the widespread learning of guitar through its ease, attractiveness, and affordability. The device uses light-emitting diodes (LEDs) to illuminate the points on a guitar neck where players should place their fingers. The LEDs are controlled through included computer software that scrolls guitar tablature on the screen. Users can control the tempo of the scrolling to match their playing level. The software also plays audio to simulate the rhythm of a metronome and the musical chords associated with the tablature. In order to develop this effective guitar aid, specific technical and practical design constraints must be followed. 2.1 Technical Design Constraints Table 1 specifies five technical design constraints. These constraints provide Light Leader the capability to be portable and to communicate more efficiently between the central processing unit (CPU) to the straps. Table 1. Technical design constraints for Light Leader. Name Description Visibility The LEDs draw 5mA to insure visibility from a distance of 3ft. Weight The hardware on the guitar neck weighs less than one pound. Height The strap between the neck and the strings has a height of less than 2mm. Current Draw The entire device requires less than 50mA. Software Size The software included uses less than 50Mb of hard disk. Delay The delay between the software sending a signal and the hardware converting the signal and illuminating the LEDs is less than 1ms. 2.1.1 Visibility Visibility refers to the ease in which the light of the LEDs can be seen during regular use of the product. To insure the visibility is adequate for viewing distances less than 3 feet, the LEDs each draw 5mA of current when lit. 2.1.2 Weight Light Leader must be of sufficient weight such that it does not interfere with normal playing of the guitar by making the guitar neck too heavy. The heaviest component of the device is the cloth on which all hardware is mounted. The next heaviest components are the microprocessors and transistors, followed by the combined weight of all the wires. The lightest component is the LEDs. The weight added to the neck of the guitar is less than one pound. 2.1.3 Height The total height of the cloth (with components) after it is wrapped around the guitar neck must be less than 2mm in height. The cloth has an approximate thickness of 0.5mm, and the LEDs have an approximate height of 1mm. This meets the requirement where the entire device rests below the guitar strings and does not interfere with regular playing.2.1.4 Current Draw To insure Light Leader operates properly when powered by the USB connection, current draw for the entire device must be less than 50mA. The recommended maximum current draw for USB powered devices is 100mA, so a maximum allowed draw of 50mA for Light Leader should greatly reduce the chances of overloading the USB connection. 2.1.5 Software Size The software bundled with Light Leader should occupy 50MB or less of hard drive space, which is not a significant amount considering recent competitive hard drive specifications in commercial personal computers (PCs). This ensures that the Light Leader software can be installed on almost any machine running Microsoft Windows XP, regardless of the history of its use. 2.1.6 Delay The timing of data from the graphic user interface (GUI) on the CPU to the LEDs on the cloth must be prompt. The communication speed must be adequately fast such that the user perceives no delay in the signals from the GUI to the LEDs. This delay should be less than 1ms to achieve this goal. 2.2 Practical Design Constraints Practical design constraints for Light Leader encompass four major areas: economic, sustainability, health and safety, and manufacturability. These practical constraints are listed below in Table II. Table 2. Practical design constraints for Light Leader. Type Name Description Economic Cost Light Leader costs $50, based upon a supply cost of $20. Sustainability Durability Light Leader is designed to operate without error for at least 3 years. Manufacturability Size Light Leader’s packaged dimensions are 10” x 5” x 3” Health and Safety Safety Light Leader’s has insulated circuitry to prevent the possibility of electrical shocks. Health and Safety Health Cloths and components used to create Light Leader should pose no threat to the health of the user. Also, the GUI alerts the user when they have been practicing continuously for two hours, to warn of possible health effects caused by strenuous playing. 2.2.1 Cost Light Leader’s most expensive components are the microprocessors and transistors. All other components, including LEDs, thin wiring, and the cloth, are very inexpensive. The materials cost of one Light Leader package including a software CD-ROM is about twenty dollars. Labor and marketing costs increase this price to a retail value of about fifty dollars.2.2.2 Durability The practical lifetime of Light Leader depends on the operational lifetime of the LEDs. Because Light Leader relies on the LEDs to provide feedback to the user, the duration of the LEDs is the main factor for the product’s durability. 2.2.3 Size The packaging size for Light Leader is 10” x 5” x 3”, which insures enough space for all hardware and software. The size also promotes the product’s visibility in the store. 2.2.4 Safety Light Leader poses no harmful materials or liquid toxins. All wires and the CPU board are covered and insulated to protect users from any electric shock that may occur. If shocks occur, they will not be life threatening because the maximum current draw is only 50mA. 2.2.5 Health The cloths and materials used to create the Light Leader pose no health risks to users. Anti-allergenic cloths prevent any form of rash or allergic reaction to the cloth used to strap the LEDs around the guitar neck. The GUI also monitors for extended periods of use and notifies the user when a practice time of two hours has elapsed. This safety measure allows the user to relax and to restore his or her concentration after engaging in multiple