Building a Smarter Light: The IBECS Network/Ballast Interface
Lighting control companies have developed products that can be specified as systems to achieve simple lighting control in buildings. Researchers at the Environmental Energy Technologies Division demonstrated in the late 1990s that components from different manufacturers could be specified, assembled, and installed, and that such systems could result in significant energy savings. However, the fragmented nature of the lighting control market means that component products from different manufacturers often do not work together well as systems. Thus, advanced lighting control equipment capable of implementing strategies such as daylighting have proved difficult to commission in the field, resulting in poor operation and user complaints. The software needed to coordinate lighting control subsystems is also immature.
To address the market shortcomings of current technology, a cooperative project involving EETD researchers and Vistron is underway to develop an integrated building equipment communications (IBECS) network. This network will allow automation of lighting systems not only to increase energy efficiency and improve building performance, but also to increase occupant satisfaction by providing occupants with a low-cost way to control their workspace lighting system. Furthermore, IBECS will provide building operators with the hardware/software infrastructure that will help them implement demand-responsive load control with confidence.
The project's goal is to design, build, and test an IBECS interface and networking system for controllable lighting devices that will enable the local and system-wide energy-efficient operation of various lighting systems and components. After an evaluation of available ballast types, microcontrollers and local area network (LAN) software, Pete Pettler (of Vistron) designed a ballast network interface around an off-the-shelf microchip set and 1-wire digital microLAN from Dallas Semiconductor that would operate commercially available 0-10 VDC (volts DC) controllable ballasts (see Figure 1). These microchips are ideally suited to web-based control of lighting and building equipment as each chip has its own IP address (264 possible addresses) and is embedded with the necessary intelligence to communicate directly with the microLAN.
To test the interface, six units were installed to control the overhead lights in an office at Lawrence Berkeley National Lab. Six two-lamp, non-dimming ballasts were replaced with 0-10 VDC two-lamp controllable ballasts. The Facilities Department installed low-voltage cabling to connect all the fixtures and connected the IBECS ballast network interfaces to each of the ballasts. The lighting system was controlled using special software installed on the office occupant's workstation. The initial test results were disappointing. Excessive electronic noise from the ballasts swamped the digital microLAN and prevented it from communicating with the interfaces.
To address this shortcoming, researchers redesigned the interface and modified the digital network. The redesign involved major modifications to the circuit to isolate the interface optically from the noise generated by the controllable ballast. This required replacing the so-called single-wire network with a four-wire powered IBECS network. (Single-wire is a misnomer. The cable actually contains two wires.) Two of the wires now supply low-voltage current to power devices on the microLAN while the two remaining wires are for signal and common. The cost per linear foot of four-wire network cable is only marginally more than two-wire cable.
Unlike the earlier interfaces they replaced, the redesigned interfaces worked without problem in the test office. Each ballast could be individually controlled as desired from the computer, and the lights dimmed quickly without discernable delay. The new design entirely eliminated the noise problems encountered previously.
Newly available microchips are a suitable platform for designing equipment interfaces that can enable low-cost networking of commercially available dimming ballasts. Electrical noise generated by the ballast in the 0-10 VDC controllable loop can interfere with digital network operation unless the interface is hardened for noise. Using optical isolation, we produced a refined IBECS network/ballast interface that could control most available 0-10 VDC controllable ballasts. We estimate that, in quantity, the cost of the interface would be about $1 to $2 to the equipment manufacturer-five to 10 times cheaper per unit than any other proposed communication system that we know of.
For more information, contact:
- Francis Rubinstein
- (510) 486-4096; fax (510) 486-4089
- Pete Pettler
- Vistron LCC
The complete report is available at the High Performance Commercial Buildings System web site.
This work is supported by the Department of Energy's Office of Building Technologies, State and Community Programs.