What makes an LED driver IoT-compatible?

Article By : Yoelit Hiebert

One manufacturer’s efforts to meet the new LED driver standard from the IoT-Ready Alliance.

With the announcement at LightFair 2018 of the IoT-Ready Alliance’s first standard, let’s take a high-level look at the design modifications that an LED-driver manufacturer might need to make to support the new standard.

The new standard (the “V1 Specification”) addresses mechanical and electrical as well as software interfaces and is backward compatible with existing lighting controls. The standard is extremely versatile, in that it can be used with any wireless or wired network protocol, including Bluetooth Low Energy (BLE), Zigbee, Z-Wave, or WiFi.

A network socket is defined within the standard that facilitates the connection of any type of sensor or control module to any luminaire within a networked lighting system, or even with other building systems. The standard also includes a requirement of 2% or better accuracy in energy metering in support of the anticipated needs of energy efficiency programs.

The IoT-Ready Alliance V1 Specification is the first of what is anticipated to be a growing number of potentially competing specs for defining how devices in “smart” environments will interact and communicate.

Tridonic, (the technology arm of Zumbotel) has played a major role in the development of the V1 Specification and introduced its first IoT Ready LED driver based on the spec at LightFair last month. I spoke with Karl Jónsson, Chief Commercial Officer at Tridonic, about the design modifications his company made to accommodate the requirements of the V1 Specification.

To achieve compliance, Tridonic started with its higher end Excite Series driver line. The new offering is a constant current LED driver, has a lineal, low-profile form factor, 300-1500 mA adjustable output, 1-100% dimming, and a maximum output of 40 W.

Of the several modifications made, one was the replacement of the DALI interface firmware embedded in the internal microcontroller with the Smart Module Interface (SMI) digital interface specified by the V1 Specification. These changes enable communication via RJ45 to any sensor, e.g., traditional “dumb” occupancy sensors, or Zigbee or BLE sensors. Two pins of the physical RJ45 connector facilitate bi-directional SMI communication.

Aside from the two pins used by the SMI interface, the driver was also modified to provide a tap into auxiliary power to supply 24 V at up to 30 mA for external devices (such as sensors). Power is supplied via two RJ45 pins for Gnd. and VCC for Aux. Power. The four remaining RJ45 pins are left open in the specification at this time in anticipation of future capabilities, including possible Ethernet support.

Another modification was the addition of isolation so that the driver is pure Class B and SELV (Safety Extra-Low Voltage) per UL 60950-1. Double insulation was added such that there is never any connection between mains and the driver output. This reduces the burden on device manufacturers in that there is no need to add an internal power supply or isolation.

The requirement for 2% accuracy in energy metering is achieved through a combination of proprietary analog circuitry and firmware. Currently, similar products using a dedicated metering chip can typically achieve no better than 4% accuracy, so meeting the 2% requirement without adding a dedicated metering ASIC represents a significant design improvement. Analog circuitry provides the metering capability for both total power and accumulated total power. You can reset the meter via the SMI interface.

General diagnostic data, which is not required by the V1 Specification, is limited to on- and off-state accumulated hours. The expected lifetime for the driver is 100,000 hours of operation.

The new IoT Ready driver is targeted for use in Green Energy Office and similar types of projects for which energy efficiency is a major objective and also for which utility rebates and incentives are typically available.

I’ll look at other IoT lighting efforts next month.


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 —Yoelit Hiebert has worked in the field of LED lighting for the past 10 years and has experience in both the manufacturing and end-user sides of the industry.




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