Fortunately, a repeater provides a practical solution for both of these problems in any X-10 compatible installation. In the X-10 standard command protocol, a controller sends the signal twice, back-to-back. The repeater listens to the first signal, then transmits on top of the second signal. It can boost a weak 25 mV signal to a 5V level that receivers can easily hear. The repeater also concurrently transmits on to the other pole in a home wiring system.

The Importance of Repeaters in Powerline Carrier Home Automation Systems

Damon Bruccoleri | Leviton Manufacturing Co. Inc.

The Importance of Repeaters in Powerline Carrier Home Automation Systems
By Damon Bruccoleri, PE Senior Engineer,
Lighting Control Division Leviton Manufacturing Co. Inc.

Fortunately, a repeater provides a practical solution for both of these problems in any X-10 compatible installation. In the X-10 standard command protocol, a controller sends the signal twice, back-to-back. The repeater listens to the first signal, then transmits on top of the second signal. It can boost a weak 25 mV signal to a 5V level that receivers can easily hear. The repeater also concurrently transmits on to the other pole in a home wiring system. 


At the risk of preaching to the converted, let's quickly summarize the distinct advantages of powerline carrier home automation systems. Expensive and often messy retrofit wiring is not required because the home's existing AC wiring provides the backbone for the system. A homeowner can start with a modest installation and expand it at any time as needs and budget dictate. Obsolescence isn't an issue: X-10 compatible devices have been around almost 25 years and new products sharing the same protocol are continually introduced to the market. Today's options include programmable whole-house scheduling of lighting and appliances, whole-house scene-lighting control, wireless remote control, motion detectors and security system interface. On top of all of this, there's a very easy way to help eliminate some of the problems that can occur in powerline carrier systems. That's why home automation professionals should understand the importance of installing a repeater.

Powerline carrier systems depend on command signals sent from controllers to receivers via the home's AC wiring. In reality, two problems can occur that prevent signals from reaching receivers, resulting in erratic system performance. The first is signal attenuation caused by the distance the signals have to travel throughout the home. A command signal may be 5V when it's sent from a controller, but it could possibly travel hundreds of feet along the AC wiring in a home. By the time it reaches a receiver, the signal could be attenuated below the minimum level the unit can hear. The second problem is the inability of signals to be transmitted on both poles in residential 120/240V single-phase systems. In this case, the signal simply never gets to a receiver.

Fortunately, a repeater provides a practical solution for both of these problems in any X-10 compatible installation. In the X-10 standard command protocol, a controller sends the signal twice, back-to-back. The repeater listens to the first signal, then transmits on top of the second signal. It can boost a weak 25 mV signal to a 5V level that receivers can easily hear. The repeater also concurrently transmits on to the other pole in a home wiring system. 

DHC Repeater/Coupler (Catalog Number HCA02)

                                                  Line Callout 2 (No Border): Repeater boosts the signal on second half of transmission and transmits on second phase concurrently.

Transmitted signal with repeater


Figure 1 - Original and Repeated Standard Command Signals.

Extended command signals are the type sent by controllers to multiple addresses simultaneously, such as in group DIM/BRIGHT commands or scene lighting commands. In the case of scene lighting, controllers send DIM, BRIGHT, ON or OFF commands to separate light fixtures at individual addresses, coordinating all into distinct user-selected lighting scenes. Repeaters handle extended commands a bit differently than a standard command. The controller sends the extended command once. The repeater will listen to the signal and transmit it a second time back-to-back with the original signal. An important feature for a repeater is the ability to sense when noise is present on the AC line. Noise generated by devices such as relays and motors turning on and off will obfuscate command signals sent by controllers. If the repeater senses this jamming, it waits 2 half-cycles and then transmits a second time. This works well because devices that transmit extended codes need to observe a bus-access protocol. These devices will delay transmitting until the repeater has finished getting its signal through. There are some heuristics included in this algorithm. Some extended commands, such as the group-execute ones, are made particularly more sensitive and the repeater will become more aggressive in its retransmit algorithm.

An installer should realize a limitation of this type of repeater. It will only repeat the original signal; it will not repeat an already-repeated signal. This could be a consideration in large installations. If a controller is not successfully communicating with a receiver, you will need to find an "in-between" point of the two devices where you can place a single repeater. A large installation may have multiple locations with controller-receiver signal problems. To solve this, multiple repeaters can be installed in a single system. A second repeater can be placed at the in-between point of another pair of controller-receivers. This process of adding repeaters can be continued until successful communication is verified between all devices. Most installers, however, take a simpler, more direct approach. They put a repeater at each of the service panels and sub-panels in the home. This is the "nuke-em" with signal strategy, and it usually works very well.

Repeaters are typically mounted at the electrical entry to the house in a separate metal enclosure using two 15-amp breakers dedicated to the device. The repeater itself consumes less than 5 watts. Dedicated breakers are recommended because a breaker with an appliance load could attenuate command signals. A repeater will typically have three connections; a white-neutral, a red-hot (where the repeater draws it power), and a black-hot. This is not a do-it-yourself project for homeowners-An electrician must install the device. Once the repeater is installed and the circuit breakers are turned on, the device should have a power/indicator light that shows the device received a reset.

In addition to amplifying and coupling command signals, repeaters can provide valuable diagnostics for X-10 compatible systems. In some devices, an error lamp blinks when there is significant noise (more than 50 mV) on the powerline. This is an important indicator because line noise at this level can disable some X-10 compatible devices that do not have a noise rejection feature. Leviton's new Repeater features IntelliSense™, a noise rejection circuit that allows the repeater to work even when the device is detecting noise.

Repeaters can also provides a built-in test feature. When the Test button is pressed, a command test signal is transmitted. An installer can then measure signal strength levels throughout the home. The repeater continues to transmit the test signal until any controller is actuated in the house. A repeater with a combination Power/Signal light is also helpful because it indicates when the repeater has detected and retransmitted a powerline code.

Choose a repeater that offers a beefed-up power supply that will not fade out or gap during long dimming commands. Another consideration is that since the repeater sits at the service entrance, it is among the first devices to be "hit" when any surges or spikes are present on the power grid. Look for new model repeaters that have upgraded from typical Zener diodes to TVSS diodes. This will benefit consumers by improving the ruggedness of the device and its ability to withstand voltage surges. Note that it is a good idea to protect the repeater and all home automation system components with a quality whole-house surge protector.

The Leviton Manufacturing Company's new Decora Home Controls (DHC) Repeater HCA02 provides all the system performance solutions and enhancements mentioned here. For any Leviton DHC or X-10 compatible installation, the HCA02 repeater will literally boost overall system performance and reliability. Leviton also offers a complete selection of DHC powerline carrier products, including new devices with one-button programming and 2-way communication capabilities, as well as high-quality whole-house surge protective devices.

The content & opinions in this article are the author’s and do not necessarily represent the views of HomeToys

Comments (0)

This post does not have any comments. Be the first to leave a comment below.


Post A Comment

You must be logged in before you can post a comment. Login now.

Featured Product

Video Mount Products IWB-1B In-Wall Box

Video Mount Products IWB-1B In-Wall Box

As flat panels themselves become increasingly slimmer, customers are looking for even more ways to get these mounted TVs and monitors as flush with the wall as possible. The Video Mount Products IWB-1B is an in wall box that allows up to a 32-inch flat panel to fully collapse into a wall. It installs easily between two 16-inch on center wooden studs, has integrated cable and electrical knockouts, and a high load capacity. The IWB-1B works with the LCD-1B and LCD-2537B mounts. The IWB-1 is yet another option for discerning installers and customers who demand both aesthetic appeal as well as the famed VMP reliability. Whether in the office, commercial install, home, or any other application where a low-profile wall mounted flat panel option is desired, the VMP IWB-1B is the answer.