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Questions and Answers
What is one main objective of street lighting?
What is one main objective of street lighting?
What is the illumination level required for high traffic density according to standards?
What is the illumination level required for high traffic density according to standards?
Which lighting technology is generally recommended for low traffic density?
Which lighting technology is generally recommended for low traffic density?
Why should the percentage of glare be minimized in street lighting?
Why should the percentage of glare be minimized in street lighting?
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Which principle is associated with the visibility of obstructions in street lighting design?
Which principle is associated with the visibility of obstructions in street lighting design?
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What characteristic should the replacement of lighting accessories have?
What characteristic should the replacement of lighting accessories have?
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What is an economic consideration in street lighting design?
What is an economic consideration in street lighting design?
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Which lighting method is suggested for medium traffic density?
Which lighting method is suggested for medium traffic density?
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What is a primary use of the lamp mentioned in cinema projectors?
What is a primary use of the lamp mentioned in cinema projectors?
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Which component is used to control the firing angle in a TRIAC dimmer circuit?
Which component is used to control the firing angle in a TRIAC dimmer circuit?
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What is the purpose of using a DIAC in a TRIAC dimmer circuit?
What is the purpose of using a DIAC in a TRIAC dimmer circuit?
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Which of the following is NOT a purpose of lighting control?
Which of the following is NOT a purpose of lighting control?
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How are TRIAC-operated dimmers superior to thyristor-operated dimmers?
How are TRIAC-operated dimmers superior to thyristor-operated dimmers?
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What is an important factor to consider when selecting a light fitting for indoor lighting?
What is an important factor to consider when selecting a light fitting for indoor lighting?
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When dimming lights using a TRIAC, which components are charged for negative half cycles?
When dimming lights using a TRIAC, which components are charged for negative half cycles?
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What percentage of light is typically reflected on ceilings and walls in a semi-indirect lighting scheme?
What percentage of light is typically reflected on ceilings and walls in a semi-indirect lighting scheme?
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Which point is a key consideration for lighting control in a workspace?
Which point is a key consideration for lighting control in a workspace?
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Which lighting scheme does not use a reflector on the light source?
Which lighting scheme does not use a reflector on the light source?
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What is a characteristic of the indirect lighting scheme compared to the semi-indirect scheme?
What is a characteristic of the indirect lighting scheme compared to the semi-indirect scheme?
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What is a major requirement for an illumination scheme in terms of maintenance?
What is a major requirement for an illumination scheme in terms of maintenance?
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Which of the following lamps is specifically listed for decorative and stage lighting?
Which of the following lamps is specifically listed for decorative and stage lighting?
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Which reason is NOT typically associated with the use of decorative lighting?
Which reason is NOT typically associated with the use of decorative lighting?
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Which of the following characteristics should an illumination scheme possess?
Which of the following characteristics should an illumination scheme possess?
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Which type of lamp is commonly used in stage lighting for its varied color outputs?
Which type of lamp is commonly used in stage lighting for its varied color outputs?
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What is the preferred lux level for an operation theater's working plane?
What is the preferred lux level for an operation theater's working plane?
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For which application is decorative lighting typically NOT utilized?
For which application is decorative lighting typically NOT utilized?
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Which of the following lighting options is typically used on an operation table?
Which of the following lighting options is typically used on an operation table?
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What aspect of an illumination scheme addresses the issue of fatigue from bright lights?
What aspect of an illumination scheme addresses the issue of fatigue from bright lights?
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Which type of lighting scheme provides the least glare and shadows?
Which type of lighting scheme provides the least glare and shadows?
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What type of lamps can sometimes be used as an anti-bacteria source in operation theaters?
What type of lamps can sometimes be used as an anti-bacteria source in operation theaters?
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What should an effective illumination scheme be free from?
What should an effective illumination scheme be free from?
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How can the control of an illumination scheme be described?
How can the control of an illumination scheme be described?
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Which type of lamps are primarily utilized in agriculture or horticulture premises when natural sunlight is insufficient?
Which type of lamps are primarily utilized in agriculture or horticulture premises when natural sunlight is insufficient?
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What is the general illumination requirement for railway platforms?
What is the general illumination requirement for railway platforms?
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Which lamps are specifically used in greenhouses for energy saving purposes?
Which lamps are specifically used in greenhouses for energy saving purposes?
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What type of lighting requirement calculation is similar in both agriculture and horticulture lighting and flood lighting?
What type of lighting requirement calculation is similar in both agriculture and horticulture lighting and flood lighting?
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Which wattages are common for metal halide lamps used in greenhouses?
Which wattages are common for metal halide lamps used in greenhouses?
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What is a primary function of the lighting scheme in greenhouses?
What is a primary function of the lighting scheme in greenhouses?
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Which of the following is NOT used for agriculture and horticulture lighting?
Which of the following is NOT used for agriculture and horticulture lighting?
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What is a specific requirement for railway platform lighting?
What is a specific requirement for railway platform lighting?
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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.
