99.9% reliable

Universal Powerline Bus (UPB) is a reliable and sophisticated home automation system that can be used to interact with and control electric devices over existing AC electrical powerlines.

Developed by Powerline Control Systems (PCS), the protocol allows for excellent communication reliability and status information for signaling to and from compatible devices. But exactly how does it work?

Pulse

The UPB system communicates with devices by transmitting digitally encoded data, in the form of precisely timed high amplitude electrical pulses, which are capable of travelling long distances. These UPB pulses are designed to operate by conforming to a standard hardware and software model, known as the “UPB System Model”.

Because the system communicates via powerline, if for any reason powerline messaging fails (which is a very rare occurrence), devices can retry until the messages eventually go through.

When UPB devices communicate, they send out precisely timed pulses at specified points on the AC wave. As there are 120 AC half-cycles per second (at 60Hz), and since each pulse can encode 2 bits of digital data, communication has a raw speed of 240 bits per second, which is perfectly reliable and adequate for signaling and control interaction.

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The technical details

The electrical UPB pulses are superimposed on top of the normal AC waveform, and are transmitted in the UPB frame at a special low noise region toward the end of the AC halfcycle. 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.

At the end of every Communication Packet is an Acknowledgement Frame, which is a single frame in which the transmitter generates no pulses. This frame receives a special pulse, called the ACK Pulse, from the receiving device indicating that the packet was fully received.

A complete UPB Communication Packet is made up of:

A Preamble Byte: A special 8-bit sequence (10010110)

Packet Header: 5-byte field consisting of a 2-byte Control Word, and a single byte each for a Network ID, a Destination ID, and a source ID

Message Data: A variable length (0 to 18 byte) field, containing the actual payload of the packet

Checksum: a single byte used for computer summing up of all the other bytes.

The Universal Powerline Bus protocol is very complex, so if you’re interested in the nitty-gritty, check out UPB’s official white paper. It explains everything from the precise workings of the pulse to how to construct a command.

UPB applications

Examples of UPB applications include turning a device on and off, and brightening or diming a device.

Turning a device on and off

A device is turned on by using the “Goto” command in a Direct Packet, with the device’s Network ID and Unit ID embedded in it. Upon receiving this command, the device will turn on to the specified level at the specified fade rate. You can also specify a level and an optional fade rate to use in switching the device off; to turn off, use the “Goto” command again, and the receiving device will turn off at the specified fade rate.

Brightening a device

UPB allows you to command a device to brighten and dim through separate commands. Use the “Fade Start” command in a Direct Packet, again with the device’s Network ID and Unit ID embedded in it to brighten. On getting this command, the device will start fading towards 100% at the specified fade rate. You can dim a device by using the “Fade Start” command. A device is then automatically stopped from brightening.