CLD Controls and Dimming 3 — Questions and Answers
Question 1: DMX512 is a unidirectional protocol. What limitation does this create in a lighting control system?
- Maximum of 128 fixtures per universe
- The controller cannot receive feedback or status from fixtures (Correct answer)
- Fixtures cannot be individually addressed
- DMX requires a dedicated power supply for each fixture
Correct answer: The controller cannot receive feedback or status from fixtures
Because DMX512 is one-way (controller to fixtures), it provides no feedback path, so the controller cannot confirm fixture status, lamp failure, or actual output level.
Question 2: An RDM-enabled system extends DMX512 by adding which capability?
- Wireless transmission of DMX data
- Bidirectional communication for device discovery and monitoring (Correct answer)
- Support for more than 512 channels per universe
- Integration with BACnet building automation
Correct answer: Bidirectional communication for device discovery and monitoring
RDM (Remote Device Management) adds a bidirectional layer to DMX512, enabling the controller to discover, configure, and receive status reports from fixtures.
Question 3: In a Lutron GRAFIK Eye QS system, what is the function of the 'fade time' parameter in a scene?
- The delay before the scene activates after a button press
- The time it takes for fixtures to transition from their current level to the scene level (Correct answer)
- The duration the scene remains active before auto-off
- The interval between scene recall cycles
Correct answer: The time it takes for fixtures to transition from their current level to the scene level
Fade time defines how long fixtures take to smoothly transition from their current dimming level to the new preset level stored in the scene.
Question 4: Which wireless lighting control protocol operates in the 900 MHz band and is developed by Lutron for its Caseta and RadioRA product lines?
- Zigbee
- Z-Wave
- Clear Connect (Correct answer)
- Thread
Correct answer: Clear Connect
Lutron's proprietary Clear Connect protocol operates in the 900 MHz band, offering better wall penetration and less interference than 2.4 GHz protocols.
Question 5: A lighting control network uses BACnet/IP. What is the primary reason a lighting designer would specify BACnet integration?
- To achieve lower installation cost than standalone dimmers
- To allow the lighting system to communicate with the building's HVAC and BMS on a common platform (Correct answer)
- To enable DALI addressing over Ethernet
- To increase the number of DMX universes available
Correct answer: To allow the lighting system to communicate with the building's HVAC and BMS on a common platform
BACnet/IP allows the lighting control system to exchange data with the building management system (BMS), enabling coordinated control with HVAC, shading, and other building systems.
Question 6: What does the term 'zone' mean in the context of a lighting control system?
- A geographic area covered by a single wireless access point
- A group of luminaires controlled together as a single channel or unit (Correct answer)
- A dimmer's overcurrent protection territory
- A time-based scheduling window
Correct answer: A group of luminaires controlled together as a single channel or unit
A zone is a group of luminaires that are controlled together, responding to a single control signal or preset level as though they were one fixture.
Question 7: Zigbee-based lighting controls form a mesh network. What is the key benefit of a mesh topology for wireless lighting?
- Each device requires its own dedicated gateway
- Devices relay signals through each other, extending range and providing redundant paths (Correct answer)
- Mesh networks use less bandwidth than star topologies
- All fixtures must be within direct radio range of the controller
Correct answer: Devices relay signals through each other, extending range and providing redundant paths
In a Zigbee mesh, mains-powered devices act as routers, relaying messages between nodes and extending range while providing multiple redundant communication paths.
CLD Controls and Dimming 3
DMX512 is a unidirectional protocol.
What limitation does this create in a lighting control system?