ELD-3110 wa2

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Thomas Edison State College *

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311

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Electrical Engineering

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Jan 9, 2024

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docx

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Mike Messier WA2 ELD-3110 Questions 1. Why is it necessary to use a resistor in series with an LED? A. LEDs (Light Emitting Diodes) are current-driven devices and have a specific voltage-current relationship. Placing an LED in a circuit without a resistor can result in excessive current flow, causing the LED to overheat and ultimately fail. The resistor in series helps limit the current flowing through the LED, protecting it from damage due to excessive current. (2010, Cjdelphi) 2. What is pulse width modulation? How can it be used to control the brightness of an LED? A. PWM is a technique used to control the average power delivered to a load by rapidly switching it on and off at varying intervals. For controlling LED brightness, the LED is turned on and off at a rapid pace. By varying the width of the on-time (duty cycle), the apparent brightness of the LED changes. When the LED is on for longer periods (higher duty cycle), it appears brighter, and when it's on for shorter durations (lower duty cycle), it appears dimmer. (2023, Wan) 3. How can a photoresistor be used to sense the level of lighting? A. A photoresistor's resistance changes based on the intensity of incident light. In a voltage divider circuit where a photoresistor and a fixed resistor are connected in series, the voltage across the photoresistor changes as the light level changes. By measuring this voltage using an analog input on a microcontroller or other devices, the level of lighting can be determined. Higher light levels result in lower resistance and higher voltage output, while lower light levels increase resistance and decrease voltage. (2022, Storr) 4. Describe an RGB LED. How can it be used to produce different colors? A. An RGB LED integrates three distinct diodes—red, green, and blue—within a single package. The independent regulation of each diode's intensity enables the creation of a diverse color spectrum. Variations in the intensity of emitted red, green, and blue light generate a range of colors. For instance, blending red and green yields yellow, combining green and blue produces cyan, and mixing red and blue creates magenta. By manipulating the intensities of these primary colors, a comprehensive array of hues can be achieved. The control of RGB LEDs is commonly managed through microcontrollers or dedicated LED driver circuits. (2007, IEEE Xplore)

Mike Messier WA2 ELD-3110 Reference: Charaterizing leds for mixture of colored led light sources. (n.d.). https://www.researchgate.net/publication/4308940_Charaterizing_LEDs_for_Mixture_of_ Colored_LED_light_sources Cjdelphi. (2010, June 26). Led’s are current driven . All About Circuits. https://forum.allaboutcircuits.com/threads/leds-are-current-driven.39855/ Storr, W. (2022, August 6). Light sensor including Photocell and LDR Sensor . Basic Electronics Tutorials. https://www.electronics-tutorials.ws/io/io_4.html Wan, M. (2023, July 24). What is PWM dimming? A method for controlling the brightness of LED lights . LEDYi Lighting. https://www.ledyilighting.com/led-pwm-dimming/

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