Triac Operated Dimmer and Lighting Control
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Questions and Answers

What is one main objective of street lighting?

  • To make the road clearly visible (correct)
  • To reduce energy consumption in urban areas
  • To enhance the aesthetic value of surrounding buildings
  • To provide surveillance for safety

    • What is the illumination level required for high traffic density according to standards?

  • 20-30 lux (correct)
  • 30-40 lux
  • 5-10 lux
  • 10-15 lux

    • Which lighting technology is generally recommended for low traffic density?

  • Halogen lamps
  • CFL, LED, and fluorescent tube (correct)
  • Sodium vapour lamp
  • Metal halide lamp

    • Why should the percentage of glare be minimized in street lighting?

    <p>To reduce chances of accidents</p> Signup and view all the answers

    Which principle is associated with the visibility of obstructions in street lighting design?

    <p>Specular-reflection principle</p> Signup and view all the answers

    What characteristic should the replacement of lighting accessories have?

    <p>It should be simple</p> Signup and view all the answers

    What is an economic consideration in street lighting design?

    <p>Making the system economical</p> Signup and view all the answers

    Which lighting method is suggested for medium traffic density?

    <p>Sodium vapour lamp and mercury vapour lamp</p> Signup and view all the answers

    What is a primary use of the lamp mentioned in cinema projectors?

    <p>Search light</p> Signup and view all the answers

    Which component is used to control the firing angle in a TRIAC dimmer circuit?

    <p>Resistor-capacitor combination</p> Signup and view all the answers

    What is the purpose of using a DIAC in a TRIAC dimmer circuit?

    <p>To provide a unidirectional pulse</p> Signup and view all the answers

    Which of the following is NOT a purpose of lighting control?

    <p>Maximizing energy consumption</p> Signup and view all the answers

    How are TRIAC-operated dimmers superior to thyristor-operated dimmers?

    <p>They can conduct both positive and negative half cycles</p> Signup and view all the answers

    What is an important factor to consider when selecting a light fitting for indoor lighting?

    <p>Color of light resembling daylight</p> Signup and view all the answers

    When dimming lights using a TRIAC, which components are charged for negative half cycles?

    <p>C1 through R1</p> Signup and view all the answers

    What percentage of light is typically reflected on ceilings and walls in a semi-indirect lighting scheme?

    <p>70 to 80%</p> Signup and view all the answers

    Which point is a key consideration for lighting control in a workspace?

    <p>Minimizing shadows</p> Signup and view all the answers

    Which lighting scheme does not use a reflector on the light source?

    <p>General lighting scheme</p> Signup and view all the answers

    What is a characteristic of the indirect lighting scheme compared to the semi-indirect scheme?

    <p>More glare and shadows</p> Signup and view all the answers

    What is a major requirement for an illumination scheme in terms of maintenance?

    <p>Maintenance should be less.</p> Signup and view all the answers

    Which of the following lamps is specifically listed for decorative and stage lighting?

    <p>Metal Halide Lamp</p> Signup and view all the answers

    Which reason is NOT typically associated with the use of decorative lighting?

    <p>To reduce energy consumption</p> Signup and view all the answers

    Which of the following characteristics should an illumination scheme possess?

    <p>Good appearance and fewer glares.</p> Signup and view all the answers

    Which type of lamp is commonly used in stage lighting for its varied color outputs?

    <p>Multi colour LED Lamp</p> Signup and view all the answers

    What is the preferred lux level for an operation theater's working plane?

    <p>400 to 600 lux</p> Signup and view all the answers

    For which application is decorative lighting typically NOT utilized?

    <p>Lighting of highways</p> Signup and view all the answers

    Which of the following lighting options is typically used on an operation table?

    <p>Bunched filament lamps or focus lamps.</p> Signup and view all the answers

    What aspect of an illumination scheme addresses the issue of fatigue from bright lights?

    <p>Designing for fewer glares.</p> Signup and view all the answers

    Which type of lighting scheme provides the least glare and shadows?

    <p>Semi-indirect lighting scheme</p> Signup and view all the answers

    What type of lamps can sometimes be used as an anti-bacteria source in operation theaters?

    <p>Ultraviolet lamps or tubes.</p> Signup and view all the answers

    What should an effective illumination scheme be free from?

    <p>Ash, smoke, or air pollution.</p> Signup and view all the answers

    How can the control of an illumination scheme be described?

    <p>Multicolour light intensity control is possible.</p> Signup and view all the answers

    Which type of lamps are primarily utilized in agriculture or horticulture premises when natural sunlight is insufficient?

    <p>High pressure sodium lamps and metal halide lamps</p> Signup and view all the answers

    What is the general illumination requirement for railway platforms?

    <p>100-150 lux</p> Signup and view all the answers

    Which lamps are specifically used in greenhouses for energy saving purposes?

    <p>CFL and fluorescent tubes</p> Signup and view all the answers

    What type of lighting requirement calculation is similar in both agriculture and horticulture lighting and flood lighting?

    <p>Lighting calculations</p> Signup and view all the answers

    Which wattages are common for metal halide lamps used in greenhouses?

    <p>75W, 250W, 400W</p> Signup and view all the answers

    What is a primary function of the lighting scheme in greenhouses?

    <p>To provide environmental conditions for plant growth</p> Signup and view all the answers

    Which of the following is NOT used for agriculture and horticulture lighting?

    <p>T-5 fluorescent lamps</p> Signup and view all the answers

    What is a specific requirement for railway platform lighting?

    <p>Good platform lighting for passenger safety</p> Signup and view all the answers

    Study Notes

    Triac Operated Dimmer

    • Triac operated dimmer overcomes the limitations of thyristor operated dimmer
    • Triac is two SCRs connected back to back with the gate terminal being common
    • It conducts both +ve and -ve half cycles
    • Capacitors C1 and C2 charge through R1 and R2, and discharge through the gate terminal
    • This determines the firing angle, or conduction angle.
    • The firing angle is controlled by the values of R2C2 for +ve cycles, and R1C1 for -ve cycles.
    • Diac is used in series with the gate to achieve a unidirectional pulse
    • This method is most commonly used for light intensity control as well as other applications like fan regulators

    Purposes of Lighting Control

    • The objective of lighting control is to provide the optimal lighting conditions for various applications
    • Minimise shadows, glare, and ensure uniform distribution of light across the working plane
    • Ensure color temperature of light is suitable for the application, often opting for daylight-like illumination
    • Allow for turning lamps on and off
    • Ability to control the amount of light emitted by lamps, often referred to as dimming
    • Different light sources are available for various situations, such as fluorescent tubes for daylight-like lighting.

    Street Lighting

    • Should make objects clearly visible to vehicle drivers
    • Appeal aesthetically to visual appeal
    • Increase community value
    • Light intensity should be determined by traffic density
    • High traffic density: 20-30 lux
    • Medium traffic density: 8-15 lux
    • Low traffic density: Minimum 4 lux
    • Should illuminate objects up to 30 mtr
    • Minimise glare to reduce the chance of accidents
    • Ensure electrical and mechanical safety
    • Simple to replace, maintain and repair, allowing for future expansion
    • Different lamp types should be selected depending on traffic density
    • High traffic density: Metal halide & Halogen lamps
    • Medium traffic density: Sodium vapour & Mercury vapour lamps
    • Low traffic density: CFL, LED, fluorescent tube

    General Principles of Street Lighting

    • Two main principles: Specular-reflection & Diffusion
    • Specular Reflection: Obstructions are visible to drivers with small angle of incidence, using reflectors. Efficiency and economy are less than direct lighting schemes, but it results in less glare and shadows.
    • Diffusion: Light source is diffused by using a diffuser to distribute the light over a wider area, which reduces glare.

    Decorative and Stage Lighting

    • Floodlights, Neon lamps, Mercury vapour lamps, Sodium vapour lamps, Multicolor LED lamps, Compact fluorescent lamps, Halogen lamps, Small capacity projector lamps, and Metal Halide lamps are commonly used
    • Used for decoration of historical buildings, gardens, interiors and exteriors
    • Used to increase the beauty of spaces and create festive moods
    • Used in various stages, often for commercial building advertisement
    • Used for domestic functions

    General Requirements for Agriculture & Horticulture Lighting

    • High-pressure Sodium & Metal halide lamps are used when natural sunlight is unavailable
    • Similar to floodlighting, with the lux level determined by specific applications
    • Fluorescent tubes and CFLs are used for energy efficiency
    • Metal halide lamps in greenhouses can range from 75W to 400W
    • Environmental conditions are also artificially regulated using lighting technology, these include temperature, humidity, wind pressure, sunlight and water percentage
    • Standard high-pressure lamps (sodium vapour and Mercury vapour) are used for 250W, 500W, 1000W, etc.

    Railway Platform Lighting

    • Essential for passenger and staff safety and comfort
    • Recommended illumination is 100-150 lux
    • T-5 fluorescent lamps are commonly used as light sources

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    Description

    This quiz explores the functionality of triac operated dimmers, focusing on how they enhance light intensity control compared to traditional thyristor dimmers. Additionally, it covers key principles of lighting control to achieve optimal lighting conditions while minimizing shadows and glare.

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