Universal powerline bus

Universal powerline bus (or UPB) is an industry emerging standard for communication among devices used for home automation. It uses power line wiring for signaling and control.

UPB was developed by PCS Powerline Systems of Northridge, California and released in 1999. Based on the concept of the ubiquitous X10 standard, UPB has an improved transmission rate and higher reliability. While X10 without specialty firewalls has a reported reliability of 70-80%, UPB reportedly has a reliability of more than 99%.

Power-line carrier control overview

Household electrical wiring such as Romex or BX is used to send digital data between UPB devices.

While in the X10 protocol this digital data is encoded onto a 120 kHz carrier which is transmitted as bursts during the relatively quiet zero crossings of the 50 or 60 Hz AC alternating current waveform, the UPB protocol works differently.

The UPB communication method consists of a series of precisely timed electrical pulses (called UPB Pulses) that are superimposed on top of the normal AC power waveform (sine wave). Receiving UPB devices can easily detect and analyze these UPB Pulses and pull out the encoded digital information from them.

UPB Pulses are generated by charging a capacitor to a high voltage and then discharging that capacitor’s voltage into the powerline at a precise time. This quick discharging of the capacitor creates a large “spike” (or pulse) on the powerline that is easily detectable by receiving UPB devices wired large distances away on the same powerline.

UPB protocol

While transmitting, one UPB Pulse is generated each half-cycle of the 60Hz AC electrical power cycle. The generation of each UPB Pulse is precisely timed to occur in one of four predefined positions in the half-cycle of the AC powerline. The position of each UPB Pulse determines its value as either 0, 1, 2, or 3. This method of encoding data as a relative position of a pulse is a well-known and used method in digital communications known as Pulse Position Modulation (PPM). Since each UPB Pulse can encode two bits of digital information and there are 120 AC half-cycles per second (at 60Hz), UPB communication has a raw speed of 240 bits per second. Although this speed isn’t fast enough for doing high bandwidth applications it is perfectly adequate for doing command and control communication.

UPB Pulses are transmitted in a special region toward the end of the AC half-cycle known as the UPB Frame. This region was selected due to its relatively low noise characteristics and for other attributes that make it an optimum position for powerline communications. UPB Frames are synchronized to the low-to-high transition of the AC waveform (known as the AC zero-crossing point) such that one Frame starts T/Frame microseconds after the zero crossing and the other Frame starts 8,333 microseconds (one half-cycle at 60Hz) after the first one.

Controllers

UPB controllers range from extremely simple plug-in modules to very sophisticated whole house home automation controllers.

The simplest controllers are plug-in controllers that are recommended for a moderate amount of switches and devices as it becomes cumbersome to control a wide range of devices.

More sophisticated controllers can control more units and/or incorporate timers that perform pre-programmed functions at specific times each day. Units are also available that use passive infrared motion detectors or photocells to turn lights on and off based on external conditions.

Finally, whole house home automation controllers can be fully programmed. These systems can execute many different timed events, respond to external sensors, and execute, with the press of a single button, an entire "scene", turning lights on, establishing brightness levels, and so on.

Weak points and limitations

UPB has overcome the hurdles of reliability, the speed and collision of commands that X10 faces. In addition, it has also now solved the speed and reliability issues previously found in a 3 phase system. With the introducution of 3-phase couplers by PCS and Simply Automated, these prior issues no longer exist. Far superior to X10, UPB is still a powerline carrier technology which can be affected be various devices on your powerline. With changes to the UPB technology many of these problems have been overcome but some still do exist and are inherent to any form of communication send on a shared powerline.

External links

* [http://www.pulseworx.com/ Power Control Systems] , developer of Universal Powerline Bus.
* [http://www.pulseworx.com/downloads/upb/UPBDescriptionv1.4.pdf Universal Powerline Bus] , The UPB System Description.
* [http://www.AutomatedOutlet.com/ Automated Outlet] , distributor of Universal Powerline Bus.
* [http://www.homeautomationnet.com/ HomeAutomationNet] , distributor of Universal Powerline Bus.
* [http://www.smarthomeusa.com/Shop/UPB/ SmartHomeUSA] , distributor of Universal Powerline Bus.