Vol.3 No.3 2010

Research paper : Development of a sensor system for animal watching to keep human health and food safety (T. Itoh et al.)−226−Synthesiology - English edition Vol.3 No.3 (2010) sufficient. For example, if the chicken health management is to be done by temperature measurement, it is not necessary to take measurements every minute, but once in 30 minutes is sufficient. In this case, it is not difficult to keep the average current consumption to about 0.1 A for sensing and transmission, and it is possible to keep the consumption at 1.4 A or less even if combined with standby current consumption. However, like in the case of humans, there are diseases that accompany high fever and those that do not. We decide whether we should visit a hospital based on whether there is a decrease in activity, such as “I feel tired” or “I don’t have energy”, rather than basing the decision on temperature alone. Therefore, we thought that some kind of activity level sensor was needed for this animal watch sensor node. In fact, as shown in Fig. 7, in some H5N1 viruses with particularly high toxicity such as the Yamaguchi strain, death may occur without marked increase in temperature. In such cases, early detection is not possible by temperature monitoring alone, but it is known that infection estimate can be based on decreased activity level[3]. In the case where the activity level is monitored, only the activity status at the moment can be known if the measurement is taken once in 30 minutes, and it is difficult to determine whether the animal is active based on the figures of that moment only. Therefore, in this research, rather than the time-driven type where the activity is monitored and transmitted at certain intervals, we opted for the event-driven type where the monitoring and transmitting are done when an activity above some threshold takes place. The difficulty of an event-driven type is the selection of the appropriate event and setting of the threshold. One of the originalities of this research was we obtained the threshold by analyzing the data for the experimental infection of chickens and developed a suitable sensor accordingly.Also, since the power needed for transmission is proportional to the amount of messages, the shortening of the transmitted message is important as well as the reduction in transmission frequency. Other than the data itself, the message includes the overhead, such as the preamble for clock synchronization and the unique word for frame synchronization, and the ID (identification code for the node). In this study the overhead is eliminated by employing the new simultaneous multi-channel reception method, and the message is shortened by using the transmission frequency and baud rate as the ID[4]. Moreover, in theory, it is possible to create a minimal message with one-third the conventional content, composed only of the temperature data and parity bit (the simplest 1 bit error detecting code) by calculating the activity level from the transmission intervals[5].As mentioned above, to achieve the chicken health monitoring system for poultry farms, the most important technical point is achieving the low-energy consumption of the wireless sensors. To achieve this, it is necessary to set the appropriate event and threshold by experimentally determining the activities and disease conditions of the chickens, and to develop the corresponding device and node system. Table 3 is a summary of the main elemental technologies to realize the system. In this research, the experimental animal infection and analysis using the wireless sensor node, the development of the low-energy consumption MEMS sensor suitable for the event-driven method based on the data obtained from the animal experiments, and the development of other elemental devices were done according to the development process shown in Fig. 3. Then, the prototype node was fabricated, the monitoring system for the experimental poultry house was created, and the issues in applying the system to the poultry house were extracted. In the future, the working node incorporating the developed elemental devices will be developed and a monitoring system using the nodes will be created. These will be used for the demonstration in the experimental poultry house.Fig. 2 Application of the animal watch sensorTable 1 Comparison of the animal watch sensor node and the human health monitoring nodeTable 2 Example of the typical current consumption value of devices that comprise the wireless sensor nodeAnimal welfareFood safetyZoonotic infection(bird flu) measureAnimal watch sensorMental healthPetsSafe societyEnvironmentalprotectionMedicine and hygieneFarm AnimalsLaboratory Animals(Semi-) Wild AnimalsSeveral thousand yen or moreAbout 100 yen (1 US dollar or 1 euro)Node costThermosensor, activity level(acceleration) sensor, heart rate sensor, ECG sensor, etc.As for now, thermosensor and activity level (acceleration) sensorSensor typeReceiver is cell phone, communication distance is1 m or lessAt least 10 m communication performance necessaryReceiver and communication distanceCharging frequency for cell phone is acceptableRecharge impossible and basically, maintenance freePower sourceTypically watch size, several ten g is acceptable as weightIn case of chicken, few cm square, few g or lessNode size and weightHuman health monitoringnodeAnimal watch sensor node(mainly for chicken)Main specsSensorNodeAbout 650 µA(1 mW)250 µA/MIPS[2]Operation(wireless transmission)modeAbout 0.2 µA0.8 µA[2]Sleep modeWirelesscommunication(RF) ICMicrocontroller(MCU: MSP430)


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