Guest post by C. Webster Marsh, a lighting design controls specialist at HLB Lighting Design in Boston, MA. His views do not necessarily reflect those of HLB.
Lighting Controls Systems may use a wide variety of lighting controls wiring to connect their systems throughout a project. How that wiring, which may use multiple conductors, connects from device to device is an important component to identify and specify on any project. A termination is the end of a conductor and it may facilitate proper communication between devices or help avoid connecting the wrong conductors to a device. Terminations will sometimes also have very specific landing points for its conductors known as “pinouts,” which maintain a consistent connection pattern for all conductors. Below is a list of common terminations that a Lighting Controls Designer may come across.
PBG / Edison / Type B / NEMA 5-15
The most recognizable termination in North America is referred to as the Parallel Blade Ground, Edison, Type B, or NEMA 5-15 plug and receptacle. It is designed to connect 100V-125V line voltage via the two blades and grounding via the pin. While the design of this termination is for power, one can also send control signal alongside the line voltage with Power Line Carrier (PLC) controls. This is an uncommon termination for PLC, however. This type of termination, when in standard permanent receptacles, cannot be dimmed. This is to avoid accidental dimming of non-lighting components.
Wiring Nuts / Splice Connectors
Wiring Nuts or other splice connectors are a quick and easy termination method. By twisting, snapping, or pushing together stripped ends, one can create a solid connection between two or more copper conductors. Some of these are designed to be permanent, while others are designed to be added and removed multiple times. These are a great resource for a swift connection but may be very messy if connecting multiple circuits and may not be recommended for digital control signal.
Terminal Blocks are a common resource when the number of conductors becomes too great for wiring nuts alone. Often found in breaker, relay, or low voltage control panels, these terminations provide a clean and organized termination point for large quantities of wires. They also provide a higher voltage rating than the above terminations but can still be found in low voltage analogue and digital systems, in lieu of other terminations.
RJ45 / 8P8C
Commonly used for Internet connectivity, the Registered Jack #45 (RJ45) termination is a common termination for CAT5 wiring, which is a type of twisted pair conductor that many digital controls systems use to connect their devices together. RJ45 often has 8 pins and 8 connectors (8P8C), but not all protocols utilize all 8 pins and may use only 4 or 6, such as in DMX512 when CAT5 is used in lieu of other wiring. This termination is a great resource for easy installations and is growing in popularity, but care must be given to ensure that the right protocols are connected together when multiple protocols are using the same termination, because various forms of Power-over-Ethernet (PoE) exist which can damage non-PoE devices. Additionally CAT5 is not the only form of wiring used with this termination, so a Lighting Controls Designer should identify what wiring the Manufacturer recommends.
RS232 / 9-Pin D-Subminiature
The 9-pin D-Subminiature (9P D-Sub) was a common D shaped form of termination in the early days of personal computers but has since been replaced by USB as the main connector for peripherals such as mice and keyboards. The termination is still popular in lighting controls systems as a connector for RS232 protocols. RS232 is not always terminated with a 9P D-Sub and may instead use a terminal block, but the termination is often used to avoid confusion and incorrect wiring of incompatible devices. RS232 is commonly used to connect two unrelated systems using a common protocol. With the same termination point, a compatible connection point can easily be identified during installation. Additionally, a specifier can easily ascertain if a device can communicate with RS232 by locating a 9P D-Sub port on it.
3 Pin / 5 Pin / XLR / Neutrik
XLR connectors are often found in theatrical terminations, most commonly in a 3-pin or 5-pin form-factor, but other pin combinations exist. This type of termination can be accidentally referred to as “microphone cable,” but while microphone cable does use 3-pins as well, care must be given to make sure that the wire terminated is correctly rated for the application it is being used for. DMX512 wire (RS485) has a different resistance than microphone wire and using microphone wire for a DMX512 connection may result in corrupt data.
Typically, a DMX512 terminator is a 120 Ohms resistor at the end of a daisy chain. This is not a wire termination, but a data termination. Data reflections can happen in DMX512 when data reaches the end of a daisy chain and to prevent this, a resistor is placed at the end to absorb the data and prevent it from traveling backwards. This is the first thing to look for when troubleshooting a problematic DMX512 system and it should be placed at the end of every DMX512 chain, but the Manufacturer may require terminators in other locations, too. Lighting Controls Designers should consult with the Manufacturer to identify where terminators are required.
Fiber Optics are a great resource when trying to send control signal long distances, but it is also one of the more fragile conductors that a Lighting Controls Designer may specify on a project. Because of this, the terminations are very important to identify and specify. The Manufacturer of the fiber optics should be able to help guide the designer, but this termination is challenging for designers new to Fiber Optics and may be best specified by a Telecommunications or IT consultant.
A Lighting Controls Designer should know their system inside and out, including what kinds of terminations are being used. Each termination has benefits and drawbacks, and so knowing when to specify an RJ45 over a 5-Pin XLR termination can be the difference between a good and a great lighting controls design. This paper covered the most common types of terminations, but new and proprietary terminations are frequently being introduced, so Lighting Controls Designers should maintain a current working knowledge of modern terminations and techniques to stay current. To learn more about wiring, check out the Lighting Controls Association article on controls wiring here.
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