Wirelessly Monitoring Temperature in Multiple Rooms for an Energy Efficient Home

Energy efficiency is a hot topic in today's energy crisis discussion. With recent technology advancements in energy efficient technologies, new ultra-low power microcontrollers (MCUs) are helping to reduce overall energy consumption while also creating a cost effective solution for wireless applications.

Many of us have experienced temperature differences in our home, when one room's temperature is noticeably warmer or cooler than the rest of the house. The reason for this disparity is that the central air conditioning thermostat only monitors temperature at one location. However, a simple and easy solution for an intelligent temperature monitoring system exists and can create a more energy efficient home simply by monitoring temperature wirelessly across multiple rooms in a house. This method of wireless monitoring ultimately means no more messy wiring and the ability to quickly identify which part of the home is not the ideal temperature.

To achieve this type of energy efficient home, small sensors are mounted around the home and continuously transmit temperature levels wirelessly to a personal computer, providing timely and accurate information regarding the current temperature levels. With this type of data, areas of the home that may require improvements can be easily identified. Knowing which areas of the home are unable to maintain desired temperature levels can be an indication that the insulation in the home is no longer effective. A quick, simple inspection can offer feedback on whether the home needs an upgrade in insulation. In this case, installing new insulation in parts of the home is much more cost effective versus replacing insulation in the entire home.

To further increase energy efficiency, the use of intelligent home automation technology can manage air-flow by controlling motorized vents that dynamically open or close based on temperature levels. This technology can even wirelessly control window blinds based on sunlight levels, eliminating the need for expensive window tinting.

This type of home automation system can easily be deployed by using Texas Instruments' eZ430-RF2500 low cost, ultra-low-power wireless tool (Figure 1). This tool consists of TI's highly integrated MSP430F2274 microcontroller coupled with TI's CC2500 2.4GHz wireless transceiver. The MSP430 MCU has many built-in peripherals including an internal temperature sensor, eliminating additional external components. The $49 eZ430-RF2500 tool is not only a wireless temperature sensor, but also offers a complete development package for users to create their custom wireless solutions. The tool is small and discreetly mountable in any part of the home, and can drastically improve home energy efficiency with only a small upfront cost.

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The tool's firmware is pre-loaded to wirelessly monitor temperature with an included temperature monitor graphical user interface (GUI) to allow customers to quickly start the development process. The firmware is built upon TI's proprietary SimpliciTI wireless network protocol, which allows central access point networking with multiple range extenders and end devices to expand the wireless temperature monitoring network anywhere in your home (Figure 2). (SimpliciTI can be downloaded online at no extra cost.) To expand the wireless network additional wireless modules are required, which can be purchased for around $20.

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With an upfront cost of approximately $169 ($49 + 6x $20) " covering three rooms, one living room, two bathrooms and one kitchen " a user can have a fully functional, monitoring system in their home. These wireless modules are also ultra-low-power devices since each module requires only 2 AAA batteries that can last up to three years with every second of transmission. Such low-power operation can be achieved through the MSP430 MCU's intelligent low-power-modes. These modules periodically wake up from low-power-mode every one second through a timer generated interrupt to sample the room's temperature and transmit a packet to the access point. After the transmission, the modules go back to low-power-mode as illustrated in Figure 3.

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Just a few years ago, having an intelligent home monitoring system required a lot of effort. But now through the use of wireless technology and the eZ430-RF2500 tool, expensive intelligent monitoring systems with messy wiring are a thing of the past. Now, users have the flexibility to create custom wireless solutions that meet their home automation needs.