CEL ZigBeeTM/802.15.4 Application Brief
Data communication path in HVAC Systems utilising wireless ZigBee Modules

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Introduction

Building/Factory owners are faced with the physical introduction of new control and monitoring technology in both new and existing buildings in sometimes difficult and remote locations. More and more commercial operations are looking to improve their “green” credentials by addressing excessive energy usage.
Industrial Plant Monitoring, redefined as Thermostatic controllers and temperature sensors, can be specifically identified
in the following applications:
• HVAC control
• Room temperature sensors
• Series receivers
• Network coordinators
• Fan control
• Louvre Motor control
• Pump configuration and control
Wireless Technology offers the solution to the difficulty encountered in the installation of new “wired” systems; ZigBee Technology provides the most user friendly environment in which to provide these new services.

Figure 1 Typical internal wireless paths in an Industrial environment

The ZigBee HVAC Solution

The technical specification ~ ZigBee Pro or IEEE 802.15.4?
In most cases, the full ZigBee mesh network application (ZigBee Pro) will not be required for proprietary Industrial HVAC Applications. Point-to-Point (P2P) or Point-to-Multipoint (P2MP) capability will probably be the most suitable application for most User requirements. However, some proprietary applications may require small mesh networks of between 10 and 100 nodes; in these HVAC applications the IEEE 802.15.4 Wireless specification will be most
appropriate.

The ZigBee 2.4 GHz Radios communicate in P2P, P2MP and mesh networks utilising low power radio transmissions which are reliable in existing RF environments. Buildings, constructed of metal, brick and concrete, can offer challenges which ZigBee radios can overcome by navigation through mesh networks as well as ‘star’ and ‘cluster-tree’ networks.

Figure 2 Examples of Network Topologies

ZigBee Technology

Module or IC?
For Industrial HVAC applications a ‘module’ rather than an ‘IC’ is often the preferred solution; lack of internal RF engineering
design capability and the requirement for rapid time to market being key factors. Often the requirement is a low tech, wire-replacement, application where the ZigBee/802.15.4 radio is not central to the end application. Volumes are in the low to moderate region (5000 to 20,000 units) and pre-designed radios not requiring RF design expertise (and hence time and costs) become the most cost effective solution.
ZigBee IC solutions, on the other hand, require in-house (or sub-contracted) experienced wireless engineering teams where system volumes normally exceed >100,000 units per year. Applications tend to be ‘open systems’ that will implement the full ZigBee stack specification and will be price sensitive consumer markets.
AB1001

CEL’s ZigBee Ready Module Solution ~ Matrix ZMXM-400-1
CEL and LS Research (LSR) have formed a joint venture to provide ZigBee-Ready modules; LSR are responsible for the design (both hardware and software) and CEL for manufacturing and marketing of a series of ZigBee modules, including
the Matrix Module described below.

Matrix Modules offer a miniature, fully integrated transmission solution based on the Texas Instruments CC2430 transceiver IC. The Matrix Module ZMXM-400-1 features ‘Dynamic Power Configuration’ (DPC) which allows the user to drive the module at 10mW when enhanced range is required, or bypass the power amplifier for 1 mW output for low power operation; changing power output is easily implemented in the embedded software.

Applications

Software
LSR Host/Application layer provides a high level interface to the IEE802.15.4 MAC Layer via a serial interface. The LSR software pre-loaded into the Matrix module MCU has sufficient features/power for ‘module-to-module’ communication;
details of which can be found on the Matrix Evaluation Kit CD.

Figure 4 LSR Host Application Layer

Figure 5 Typical HVAC Block Diagram

2. Hotel Energy Management Systems allow the hotel operator to ensure that empty rooms are not cooled or heated thus saving energy. A wireless HVAC system consisting of Battery operated thermostats, occupancy detectors and humidity sensors will be easy to install as all units can be placed in a convenient location and are easy to retrofit due to the lack of cabling. The hotel operator can personalise the room settings for regular clients (according to their recorded profiles) at check-in.

Each HVAC unit can be connected to an energy management controller that adjusts room temperatures based on occupancy information received from the hotel’s management software.

Conclusion and Benefits

ZigBee Networks are easily retrofitted to accommodate budgets and building schedules; where there is a wired communication
connection today there is an opportunity for CEL wireless ZigBee Modules.

In most cases a full ZigBee PRO mesh is not required as systems are commonly proprietary; the P2P, P2MP and small mesh applications are normally most appropriate.

The estimated cost of design of time and money for a ZigBee solution can be briefly summarised as follows:

• Hardware ~ $20-$30K (Radio/ analog design is difficult and costly)
• Software ~ $85K (Develop, implement, and maintain ZigBee stack)
• Certification ~ $11-$32K (Each radio implementation requires certification)
  

CEL modules reduce total system time to Market

• CEL’s evaluation kit enables network prototyping in days not months ~ In house design can take many months
• CEL’s ZigBee modules get you to market quicker with proven cost-effective solutions!
• Radio design is: part engineering and part art ~ Design re-spins will add time and engineering resources to get radio “right” ~ CEL’s modules are already in production
• Failing FCC / CE certification can add months of time and cost to in house design ~ CEL’s modules have already been certified