Today the word “smart” is being added to applications or products to imply that they work autonomously in a programmable environment. From smart cars to smart meters, we are seeing a new category of products bearing some manner of intelligence. In this article, we will discuss how the ZigBee wireless protocol — suitable for short-range connectivity and control — is helping to add parking lots and street/ highway lighting to the “smart” list.
ZigBee is a technology that is based on the IEEE 802.15.4-2003 standard. It is somewhat similar to other familiar wireless protocols such as Wi-Fi, Bluetooth, 4G, and WiMAX. The most popular application using ZigBee today is for lighting fixtures in an office environment, such as wireless light switches with lamps. Other common ZigBee apps include electrical meters with in home-displays and as short-range radio connections for consumer electronics, where a low rate of data transfer is sufficient.
Figure 1: ZigBee was designed for short-range connectivity and controls, mesh, and very low power applications.
Parking lots today, whether they are located indoors or outdoors, burn a lot of energy. Depending on the lot size, many lighting fixtures are used, not only for illumination but for security purposes as well. The principal benefit of installing ZigBee-enabled motion control detectors in parking facilities is to save energy, as these detectors will automatically trigger either light shutoff or dimming to about half power when no cars are in the lot. When motion is detected, the lights will turn on, and when no further motion is detected, the lights will be instructed to resume a low energy state. Further, if on-site security personnel need to override any settings, ZigBee allows them to do so from a central control point.
If you live in a big city or frequent a large shopping mall, finding a vacant parking space in a mall, conference center, or office building can be a time-consuming, not to mention a very frustrating experience, driving around in circles until someone leaves a parking spot. Now, with smart phones gaining widespread use, imagine being alerted from your phone that a parking space is vacant and then being directed to it. Among wireless standards a designer can choose from (e.g., ZigBee/Bluetooth/Wi-Fi), ZigBee/IEEE 802.15.4 is definitely the wireless standard of choice for this application, not only because it is battery operated – saving up to 50 percent of power consumption over traditional solutions-- but also because it is capable of re-routing the signal if line-of-sight is blocked, a critical requirement since parking lot walls can be made of concrete.
Directing cars to an open spot using ZigBee technology can reduce wasted personal time for motorists along with trimming gasoline use and cost and, in turn, lower automotive emissions and improve air quality in the parking structure.
Smart street lighting and highway lighting
For street and highway lighting, ZigBee-based controllers can turn these lights on/off at a certain pre-programmed time – again saving energy. They can also dim the lights based on environmental conditions. As with smart parking lots, the city employee can control the setting from one location and can detect (whether in the control room or just receiving a text message on his/her smart phone) and replace a street light when it is burned out. A side benefit of this is enhanced safety, since smart street and highway lighting allows lights to be replaced in a timely matter.
Figure 2: ZigBee-enabled controllers can turn lights on and off on a set schedule, and can dim or raise lighting based on ambient lighting conditions.
How to choose
Smart parking lots, along with street and highway lighting, can be designed with either a chip or module hardware solution. Today there are a number of semiconductor manufacturers, such as Atmel, CEL, Texas Instruments, Freescale and many more providing ZigBee parts that are available from Digi-Key.
While chips or chipsets basically cost less than a module (particularly when chips are ordered in large quantities), there are also hidden costs, including the addition of external components (such as the antenna). The benefit of choosing a module is that all the RF and MCU related circuitry is included, along with the antenna. You do not even have to have RF experience. What is more, most of the time ZigBee modules come with certification, which makes the approval process for end products that much easier. So, if you are designing for production quantities and it is not clear cut that chips or chipsets would be more cost efficient, be sure to consider modules.
A popular ZigBee module available for these types of applications that can be found on the Digi-key website is CEL’s MeshConnect EM357 module (ZICM357P2-1). The module is based on the Ember EM357 ZigBee-compliant SOC IC. The IC consists of an RF transceiver with the baseband modem, a hardwired MAC, and an embedded 32-bit ARM Cortex-M3 microcontroller with internal RAM (12-Kbyte) and flash (192-Kbyte) memory. The device provides numerous general-purpose I/O pins and peripheral functions such as timers and UARTs.
The MeshConnect EM357 module can add a power amplifier (PA) to increase range up to 2.5 miles, providing more reliable transmission and reducing the number of nodes in your network. It is especially useful for open outdoor applications where the nodes are physically far apart or for indoor use where the nodes have to operate in a noisy RF environment. The Module’s outstanding 120-dB link budget ensures high quality connections even in harsh environments.
Developers who want to gain some familiarity with basic ZigBee networks should consider starting with Texas Instruments’ CC2530ZNP Mini kit, which is basically considered an educational tool. It is not intended as a ZigBee reference design. The kit is based on a 32-Kbyte flash MSP430, and because of this, it does not support official ZigBee profiles that are required to make ZigBee-certified products.
There are many benefits to using ZigBee technology in street and parking lot lighting applications. These benefits include energy savings, ease of central control, and the monitoring of lights for quick replacement to maintain safe lighting conditions. Both ICs and fully certified modules are available to designers of these applications. A development kit, such as the Texas Instruments’ CC2530ZNP Mini kit, would be a good starting point for lighting designers unfamiliar with ZigBee systems.
- David Cohen, “ZigBee helps light the future.”
- “Case study: Parking Lot Gets Smart with ZigBee,” Meshnetics.
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