Vol.3 No.3 2010
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Research paper : Development of a sensor system for animal watching to keep human health and food safety (T. Itoh et al.)−225−Synthesiology - English edition Vol.3 No.3 (2010) or estimates can be made about whether the pattern of change is for the group or the individual, or whether it is an infection or some environmental control problem. Then, a warning is issued to the farmer or a report can be sent automatically to the veterinarian or the authorities, as needed.We became aware of the necessity of downsizing, power reduction, and cost reduction of the node to realize the wireless sensor network system. The key is the utilization of the micro electro mechanical systems (MEMS) and its fusion with the related fields. MEMS are expected to be the main player of the “more than Moore” (advancement of the electronic device through diversification of its function) and has matured as the manufacturing technology for various sensing devices or man-machine interface devices. In this paper, we shall describe the experimental infection data obtained in this project, and explain the development concept of the ultra-low power (ULP) small wireless sensor node utilizing the MEMS technology.2 Animal watch sensor nodesAs mentioned before, this study is a development of a monitoring system for chicken health that can be applied to the early detection of bird flu outbreaks. The developing wireless sensor node is called the “animal watch sensor node” because it is being considered for application to wild animals and pets, as well as livestocks other than chicken (Fig. 2). Table 1 shows the comparison of the human node and the animal watch sensor node that is expected to be used with relatively small livestock such as poultry. It is important to note that the node to be developed is totally different in requirements from the ones developed for humans, and the technological hurdle for low power consumption is fairly high.Looking specifically at power consumption, the node lifespan must be about two years since the egg-laying hens are processed (as spent hen) in about 550 days[1]. Assuming the use of SR721, a silver oxide button battery weighing about 0.5 g that is also used in watches, since the official battery capacity of SR721 is 25 mAh, the average current consumption must be kept at 1.4 A or less to ensure a two year operation. The wireless sensor node is usually composed of the sensor element, sensor interface circuit, microcontroller unit (MCU), wireless communication IC, and power source. As shown in table 2, the current consumption of the microcontroller and the wireless communication IC in standby mode only is about 1 A even when low-energy consumption microcontroller is used. Therefore, achieving the current consumption of 1.4 A or less is not simple, considering the current consumption of sensor and amplifier in standby and operating modes, as well as for the microcontroller and wireless transmission during operation. Therefore, in this research, the node with average power consumption of 1 W level (current consumption 0.65 A), or 1/1000 of conventional product, is achieved by reducing the power consumption of transmission and sensing, rather than by achieving further low-power consumption for the semiconductor elements such as the microcontroller. This means that the strategy of research is to achieve low energy consumption by methods such as raising the efficiency of sensing and transmission by dramatically reducing the standby power, minimizing the frequency and quantity of sensing and transmission, or increasing the efficiency of the antenna.The most important concept in “minimizing the frequency and quantity of sensing and transmission” is the concept of “event driven”. To simply reduce the frequency and quantity of sensing and transmission, intermittent operation is Fig. 1 Image of the chicken health monitoring system“Wing band” Wing band type 6 x 30 x 0.1 mm3, 1 g Permanent use (2 years for healthy chicken)315MHz, Transmission distance 10 mAverage power consumption several µW or less (final goal 1 µW level) Piezoelectric activity level sensor Digital thermosensor Custom RF-IC Small batteryAbnormalityinformationCageCross section of poultry houseInformation for location of abnormal chickenDead chickenAbnormalchickenTemperature graphHistory of individual temperatureComparison of temperature historyFever comparisonPoultry farm managementand monitoring system

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