June 15, 2014
June 15, 2014
June 18, 2014
K-12 & Pre-College Engineering
24.857.1 - 24.857.3
LEDs & Lamps – A Friendly Affordable Gateway to Electrical Exploration ASEE 2014 Conference - K-12 Division - Curriculum Exchange AbstractSummary:This demonstration will highlight how light emitting diodes (LEDs) and incandescent lamps can be usedto explore electrical topics, substitute for otherwise expensive equipment, facilitate creative engineeringdesign projects, and provide opportunities to integrate math, science, engineering and art with real-worldissues such as energy efficiency and technology for the developing world. This session aims to empowerteachers to further explore electrical topics, despite whatever limitations they may feel in terms of funds,resources, and/or technical knowledge.Pedagogical Context:LEDs are popular and fun components that help make learning electrical topics a playful experience. Thissession will explore their many appealing applications for STEM education... 1. LEDs and lamps can be used to observe both static and dynamic circuit behavior, offering a visual method of learning about electricity and providing a substitute for expensive measurement instruments. LED brightness corresponds to current, incandescent lamp brightness corresponds to voltage. These fundamental electrical concepts are made tangible and accessible by observing them with light. 2. LEDs make for great hands-on projects that develop practical skills (such as schematic diagram interpretation, wiring dexterity, soldering, and circuit analysis) and offer compelling creative design opportunities—both technical and aesthetic. 3. LEDs are commonly used in energy efficiency improvements and products designed to make best use of limited resources in the developing world. This offers an opportunity to integrate engineering within the framework of social/world issues while including varying levels of scientific content as needed.Demonstrations:The session, poster, and handouts will showcase a selection of hands-on light-based circuit activities thatdemonstrate and help teach electrical concepts. The measurements can be performed by visualobservation without instruments. Additional DetailsThe presentation will include these and/or other similar experiments, here listed in order of target agewith annotations for various math integration opportunities (not requirements). All are compatible withphysical science and/or physics at any level. 1. LEDs and energy efficiency (Grades: K-12, Math: multiplication and beyond): A simple battery- operated LED torch will be compared to a traditional incandescent night light. Using current and voltage specifications and/or measurements, the power usage of each light source can be calculated. It will be demonstrated that the LED version uses 1/25 as much power as the incandescent night light. Additional lessons will be explored regarding the torch design process, balancing brightness versus power usage and battery life, and the benefits and opportunities that LED technology brings to our world. This is a very effective introductory project in electricity that is appropriate for any age (beyond choking hazard). Each participant will quickly design and build their own LED torch with materials and tools provided by the presenter (time permitting). 2. Potentiometer as voltage/current control (Grades: 4-12, Math: addition & subtraction): A lamp and LED will be wired such that they get dimmer and brighter as the potentiometer is adjusted. The concept of voltage division can be explored by using two LEDs. 3. Resistor as a current limiter and LED as current indicator (Grades: 5-12, Math: addition, subtraction, multiplication): Several series resistor/LED combinations will be wired in parallel. Each combination will have an identical LED and different size resistor. LED brightness indicates current, thus enabling visual confirmation of larger/smaller currents in the circuit which correspond to smaller/larger resistances. 4. Logic Probe (Grades: 6-12, Math: binary): Simple circuit with 2 LEDs and 2 resistors to indicate Hi/LO status of a digital circuit pin. 5. Alternating current (Grades: 6-12, Math: sine waves & trigonometry): A bipolar LED (or pair of opposite-wired different-colored LEDs in parallel) will be connected to an AC sine wave signal. One color will light when the positive peaks pass and the other will light when the negative peaks pass, indicating the forward/reverse current behavior of an AC system and the one-way current properties of a diode. 6. AC/DC Rectifier (Grades: 7-12, Math: sine waves & trigonometry): A single LED will be wired to an AC sine wave to demonstrate the half-wave rectifier concept (the diode only allows the positive peaks to pass). A four-LED full-wave rectifier will demonstrate the current flow as it cleverly inverts the negative peaks. An incandescent lamp will be wired to the output of both to demonstrate that the full-wave rectifier generates a smoother output. A capacitor will be added to each rectifier such that the lamp also shows the capacitor’s additional smoothing affect. 7. Capacitor charge/discharge (Grades 10-12, Math: Pre-calc & Calculus): A capacitor circuit will be wired to a pulse source such that the cap charges and discharges repeatedly. An incandescent lamp will be wired in parallel with the cap, indicating its voltage—it will grow brighter as the cap charges and dimmer as it discharges. An LED will be wired in series with the cap, indicating its current, which is the rate of change of voltage—it will light only when the voltage is changing (charging or discharging), and turn off when the cap is fully charged or discharged. The derivative/integral relationship between capacitor voltage and current can be observed dynamically in the lamp and LED as they change brightness.Example Images (with corresponding demonstration numbers from list above): 1. 3. 4. 6. 7.
Tubesing, A. (2014, June), LEDs & Lamps – A Friendly Affordable Gateway to Electrical Exploration (Curriculum Exchange) Paper presented at 2014 ASEE Annual Conference & Exposition, Indianapolis, Indiana. 10.18260/1-2--20748
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