In this article from the IEEE the inventor of Li-Fi explains how it works.
The companion blog to the book Designing With Light, 2nd Edition
In this article from the IEEE the inventor of Li-Fi explains how it works.
The current global cyber-attack, combined with last year’s “denial of service attack has me thinking about the lighting industry and IoT.
It was ironic that last year’s attack happened just days before the IES annual conference, at which IoT lighting was touted as the next big thing that everyone had to adopt or be left behind. You may recall that one aspect of that attack was that hackers recruited IoT devices like thermostats and smoke detectors. Many designers may think, “Well, sure, homeowners don’t have good security, but that wouldn’t happen to one of my corporate clients.” The current attack shows the flaw in that thinking. New tools have allowed hackers access to supposedly secure networks, and not all networks that should be secure (such as Britain’s NHS) actually are.
The question, then, is, “Why should my lighting system use IoT?” I’ve asked several friends in lighting design firms large and small and the answers I’ve received are revealing. Almost no one has a client who is asking for this. (I’ve had exactly one client who wanted the lighting system connected to the corporate LAN.) Do they want lighting systems connected to their BMS? If the client is knowledgeable and the building is large, yes, although today’s lighting systems have so many programming options we don’t need the BMS to control the lighting system. Do they want lighting systems to use Wi-Fi so that users can adjust the lights from phones and pads? Not very often. “Why would I want to give that many people authorization to change the lighting?” is the question asked, and rightly so. Do they want light fixtures with IP addresses and built-in Wi-Fi, Li-Fi, daylight sensors, occupancy sensors, temperature sensors, humidity sensors, and software that tracks shoppers or monitors space usage? “How much will that cost?” is the usual first question, followed by a strong “No.”
If we designers don’t see an artistic or operational advantage to these systems, and if our clients don’t see an advantage and aren’t asking for these systems, why all the noise about them? The answer, of course, isn’t better lighting design or increased energy efficiency, it’s money. Companies like Cisco see expanded profits from embedding Cisco sensors in every light fixture in a building, connecting all of those fixtures to Cisco POE switches and perhaps controlling the fixtures and sensors with Cisco software. Fixture manufacturers, always looking for a way to differentiate their products, jump on board. Marketing departments create hype, magazines and web sites need material, and voila! the next “must have” lighting system feature.
Who’s providing network security? The corporate IT department, I guess. Are the lighting systems vulnerable to hacking? The current and recent attacks tell us the answer is, “Yes.” Are manufacturers of IoT devices investing in security? Not really. They see it as the responsibility of someone upstream. Would anyone want a lighting system that is vulnerable to being turned off in an emergency, or reprogrammed by someone just to see if they can do it? No.
Some of the lighting systems I am designing are quite complex involving hundreds of fixtures with hundreds of addresses, multiple control protocols, and multiple points of control including touchscreens and Wi-Fi devices. One thing no one has to worry about, though, is high-jacking or corruption of the system. Each system stands alone. Software updates, if they are ever needed, are downloaded and installed via a USB key. Anyone wanting access to the system has to be within Wi-Fi range and has to hack the network. What would they get? Access to a single lighting system. There’s almost no reward and therefore there’s almost no incentive. Call me a Luddite if you like, but for now I’m going to stick to designing secure, flexible systems that provide my clients with only the features that they want at a price they are willing to pay. I’m sure that the pressure to “innovate” will eventually lead me to using these IoT systems. But for security’s sake I’m going to resist for as long as I can.
ASHRAE has announced a 30-day public review and comment period for addendum to ASHRAE/USGBC/IES Standard 189.1-2014, beginning on July 24th. The addendum that concerns lighting designers corrects and clarifies a potentially confusing requirement in which a designer may conclude that bonus lighting power control factors from Table 9.6.3 Control Factors Used in Calculating Additional Interior LPD of ANSI/ASHRAE/IES Standard 90.1 cannot be used.
More information and instructions on commenting are at https://www.ashrae.org/standards-research–technology/public-review-drafts.
On September 26, 2014 the U.S. Department of Energy issued a determination that ANSI/ASHRAE/IES Standard 90.1-2013 would achieve greater energy efficiency in buildings subject to the code than the 2010 version. The DOE analyses determined that the energy savings would be:
As a result, all states are now required to certify that they have reviewed the provisions of their commercial building code regarding energy efficiency and, if necessary, updated their codes to meet or exceed the 2013 edition of Standard 90.1. States must submit certification of compliance by September 26, 2016 or explain why they cannot comply.
Why is this happening? The DOE is required by the Energy Conservation and Production Act (42 USC 6833) to review each new edition of ANSI/ASHRAE/IES Standard 90.1, and issue a determination as to whether the updated edition will improve energy efficiency in commercial buildings. If the determination is that the new version will improve energy efficiency, that standard becomes the new nationwide minimum requirement. States aren’t required to adopt Standard 90.1, but whatever standard they develop or adopt must be at least as stringent as Standard 90.1.
Some of the changes in the new standard are:
The DOE website contains additional information, including PDFs of the analyses they conducted.
Recently a designer specified 0-10V dimming for a series of LED downlights. The electrician powered the LEDs by connecting them to a nearby breaker panel. The 0-10V control signal was generated by the lighting control system. This was a simple system that should have worked with no problems. Much to everyone’s surprise the lights would dim but they wouldn’t go off! What happened?
Dimming light sources other than incandescent is a technical challenge. It requires the ballast (for fluorescent, HID, cold cathode, etc.) or the driver (for LEDs) to precisely control the amperage and the voltage, and may also require converting the incoming AC to a DC output (for some LEDs). This is difficult for fluorescent and HID lamps because the electricity must arc from one side of the lamp to the other, and at low power levels that arc simply fails. Dimming LEDs often results in a visibly jittery dimming curve as well as a jump to zero when dimming down and a jump to on when dimming up. (This article in Electrical Construction & Maintenance is a good overview of the problems with dimming LEDs.)
In architectural lighting, however, the inability to dim all the way to zero is usually not seen as a problem. Typical dimming applications such as classrooms and meeting rooms may want to dim lights for a presentation, but some light is still desirable so that attendees can see each other for discussion and see their desktop to take notes. Dimming is acceptable as long as the dimming is smooth down to a minimum light level. In these installations the drop from, say, ten percent to zero isn’t an issue because it doesn’t happen until the room is empty and the lights are turned completely off.
With 0-10V dimming, though, the dimmer or driver is powered by the incoming line voltage, so its always operating. As a result, its minimum operating capacity is also the fully dimmed state. A 100-10% ballast or driver, for example, has a minimum output of 10% not zero. When the fader is at the bottom of its travel we would normally expect the lights to go off, but they only go to 10%. Here’s a graph showing the performance of representative LED fixtures dimmed with a 0-10V dimmer.
The solution is to provide separate switching of the line voltage delivered to the fixture. Most wallbox dimmers have a toggle switch below the fader so that the fixture can be shut off at any time. Here’s a schematic of a simple circuit.
Other solutions come from other dimming techniques, including three-wire and four-wire dimming where the line voltage and the control signal come out of the same device. This guarantees that at a minimum state power to the fixture is shut off. Other control protocols, notably DMX512, and the electronics that utilize them can usually dim to zero.
Today I was at an LED “shootout” at the New York City office of Barbizon (special thanks to John Gebbe and Scott Hali). We were looking at products that might be used in a specific application – that of lighting an auditorium or theatre. The shootout was between 26 fixtures from 17 manufacturers, all installed at a height of 10′.
Architecturally, the designer is essentially lighting three conjoined rooms: the orchestra, where the ceiling can be 35′ high or more; the balcony, where the ceiling can range from 12′ to 25′ because of the steep slope of the seating; under the balcony, where the ceiling may range from 12′ to 18′, again because of the slope of the seating.
The first part of the challenge is to find a set of fixtures that can provide even illumination in these three spaces, each one of which has a sloped floor and therefore a varying throw distance. The second part of the challenge is for all of the fixtures to dim simultaneously. Unfortunately, I don’t think we saw success. Here’s what we saw.
First, only one manufacturer had a product line for all three possible mounting conditions – pendant, surface, and recessed. That manufacturer, though, didn’t have three beam spread and/or brightness options to meet the range of typical installation heights.
Second, LED manufacturing is maturing, but it’s not mature. That means we still don’t have strong, industry-wide standards for things like color. In many cases it was difficult to use fixtures from two or more manufacturers because the color of the light produced (visually evaluated, and measured in color temperature, peak wavelength and spectral content) clearly didn’t match.
Finally, getting fixtures from multiple manufacturers to dim simultaneously proved very difficult. Each set of installed fixtures would need its own (perhaps custom) dimming curve just to get a close match, and identical performance seemed impossible. The problem here is three-fold. First, multiple control protocols would be required. The fixtures demonstrated used line voltage dimming, three-wire dimming, 0-10v DC, and DMX protocols. That’s not a deal breaker, but it is an unfortunate complication. Second, some of the LED drivers produced unacceptable dips, flickering, or pulsing of the light as they dimmed. Third, some of the LED drivers couldn’t make a smooth transition from darkness or light, or light to darkness. We saw fixtures pop on and drop out, dim up nicely but not dim out well, and dim out well but pop on. Eventually this might be as easy as working with incandescent lamps, but not yet.
The easy lesson was that, for now, the safest choice for smooth dimming from darkness to full light is still incandescent. The color of the light from fixtures in all of the installation conditions will match, the dimming curves will be the same, and they’re easy to dim.
The complicated lesson was that it is absolutely essential to mock up the proposed lighting system, using the LEDs, drivers, control protocols, and dimming equipment that will be installed. It’s the only way to be certain that the start and end of a show, when the house lights dim down and then back up, isn’t a light show of its own.