City Streetlights Become Smart: The New LED Street Lamps, Part 2

In part one of this blog series I introduced a new solution for the illumination of streets in big cities that is based on the adoption of LED lights, a smart solution in terms of efficiency and cost-reduction.

An important next step in the adoption of LED for street illumination has been taken by the company STMicroelectronics, which recently announced a smart new approach to the illumination of cities:

    In conjunction with a smart power supply, LED street lamps become intelligent devices. They gradually increase their brightness as daylight fades and automatically reduce their brightness as the sun rises. They communicate with the smart grid and pave the way to the smart cities.

The STMicroelectronics Company is expanding its portfolio in the field of electronics for smart grid systems, has produced a new solution (see Figure 1) to manage LEDs that are dimmable and can be driven by a microcontroller, in order to reduce power consumption and realize a really smart system of management of electricity, avoiding losses. These losses may be caused by commonly utilized lights, bulbs that create a waste of energy, or by a non-optimized management of power.

Figure 1

The new ST solution for smart LED driving.

The new ST solution for smart LED driving.

This new solution is available in a demo board that is based on the digital power controller STLUX385A, a controller able to drive a row of LEDS for smart-lighting applications by mean of a proprietary power conversion protocol. The core of the new ST system for the smart driving of a row of LEDs is the DALI:

    DALI (digital addressable lighting interface), standardized as IEC 929, is the new interface for lighting control solutions defined by the lighting industry. The DALI protocol is generally implemented in a DALI communication module (DCM): a serial communication circuit designed for controllable electronic ballasts. “Ballast” is a device or circuit used to provide the required starting voltage and operating current for LED.

When speaking of LEDs it’s important to keep in mind that the LED devices have to be supplied at a constant electric current, and the LED starts emitting light once the forward voltage electric threshold is reached. The electric power supplied to the LED, which is the product of the voltage and of the current applied to the LED, has to be absolutely constant and stable in time to guarantee the effectiveness of LED illumination.

In the next and final part of this blog series, more solutions from big semiconductors companies are described. Did you ever work on a LED-based smart illumination system? What types of functionality would you add to this smart system?

7 comments on “City Streetlights Become Smart: The New LED Street Lamps, Part 2

  1. Davidled
    June 10, 2014

    Summary: (1). Dimmable; (2).Reduction of power consumption; and (3). smart power management.  Based on attached circuit, features could be more than these.  Color of lighting could be changed depending on temperature range or weather condition as adding the humidity sensor in the analog circuit driver.

  2. samicksha
    June 11, 2014

    Controller user for street lights sounds good fit to environment as well, it says that its operating temperature is -40 °C up to 105 °C.

  3. etnapowers
    June 11, 2014

    DaeJ: nice post, thank you. You're right there is room for putting more intelligence in the circuitry, the humidity sensor is a valid option , another valid option is a photodiode which senses the intensity of light in a ambient and regulates accordingly the power delivered to the LED lights.

  4. etnapowers
    June 13, 2014

    @samicksha: Yes it is a really good feature, the operating temperature of the LED lights is lower: usually in the range [-40°C , 85°C] the storage temperature is in the range [-40°C , 100°C].

  5. etnapowers
    June 16, 2014

    The DALI is an interesting solution, because it is a standard board to be utilized in many application requiring a smart driving of the LED lights and it is  a modular approach.

  6. RedDerek
    June 26, 2014

    I posted this on part 1, but I still believe it could be applicable here.

    Have the controller look at a temperature feedback from the heatsink. Then throttle back the current to keep the LED temperature from exceeding a maximum value. This would help ensure longer life.

    Heat is one of the killers for LEDs.

  7. yalanand
    June 30, 2014

    The LED driver feature is a really good feature as it is good on regulating temperatures of the LED lights. It has also successfully been able to store the energy that that is being generated by the driver. The good thing is that the city street lights have now become smart. This means that they will be able to function more effectively and they will be able to be distributed through out the country. The LED driver feature is without a doubt a win because cities will be able to use LED street lamps.

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