A New Wireless Sensor Used in Grain Pests Detection

Shi-Feng QI School of Mathematics and Computer Science

Panzhihua University, Panzhihua, Sichuan, China

E-mail: qeverest@163.com.cn

Yan-Hua LI School of Mathematics and Computer Science

Panzhihua University, Panzhihua, Sichuan, China

E-mail: liyanhua5566@163.com.cn

Abstract—At present, there are many detection methods of the grain pest, but these detection methods have many defects, such as low efficiency, poor accuracy, great implementation difficulty, detection not in time, etc. To solve the above defects, this paper provides a wireless sensor which can detect the species and quantity of the grain pest at the same time. Its main principle is: when pests go through detection electrodes of the sensor, its capacitance value will change. Due to different species of the grain pests have different dielectric constant, then, the change range is also different. According to different capacitance value range, the capacitance detection circuit determines the species of pests, and records the changing times of capacitance to determine the quantity of grain pests. The sensor has the advantages of the low power and the wireless transmission of the detection data and so on, and is suitable for large range of promotion. This has great significance on the China’s grain safety.

Keywords-grain insect pest, wireless sensor, pest detection electrodes, capacitance detection circuit

I. INTRODUCTION

In the daily custody of grain bulk, the insect pest often occurs. So, monitoring the pest occurrence situation everywhere in grain bulk must be done to determine the species and quantity of the grain pest, and whether to take preventive measures. And to ensure the concentration, time and manner of the pesticide application in the fumigation phase, and ensure the grain storage security[1,2]. At present, the detection methods of the grain pest include the manual sampling, the light blocking automatic detection, the video detection and the acoustic detection, etc. The manual sampling is both laborious and time-consuming, and can not real time detect. In the light blocking automatic detection, the light-emitting diode(LED) and the photodiode are installed on both sides of the channel the pests freely falling into the trap device, and are perpendicular to the channel. In the process of falling, the pest blocking out the light which the LED is emitting to the photodiode triggers a count, then counts the number of pests in turn. This method can't distinguish the species of pests, and also cannot distinguish between the impurities in grain and the pests. The power consumption is big, and it only uses the wire transmission. In the concrete implementation, the layout of the sensor is very difficult, and the position moving is very inconvenience. In the video detection method, the video camera is installed under a transparent mothkilling board, and uses the video

images or photos to manually distinguish the species and quantity of pests. The power consumption is big, The manufacturing cost and the use cost is high, the existing video detection method is also wire transmission, and can not realize the automatic monitoring of the pests data. The acoustic detection method distinguish the species of pests by the sound of the activity, but can not distinguish the quantity of pests, and is acutely affected by the external interference, the concrete implementation is very difficult, there is almost no application example at present.

The above method show that the existing grain pest detection methods have many defects, such as low efficiency, poor accuracy , great implementation difficulty, detection not in time, etc. Because of the need of grain storage security and the development of technology, the grain pest detection is developing towards automatic, accurate, wireless monitoring. To solve the defects in the current grain pest detection, this paper provides a wireless sensor which can detect the species and quantity of the grain pest at the same time. It has the advantages of the low power and the wireless transmission of the detection data and so on[3], and is suitable for large range of promotion, Which has great significance on the China's grain safety.

II. A DESIGN SCHEME OF THE SENSOR

A. Overall Design

InletWormhole

Battery andWirelessSensingModule

CapacitanceDetection

Circuit

PestDetectionElectrodes

Figure 1. Overall Structure Diagram for The Sensor

2012 International Conference on Control Engineering and Communication Technology

978-0-7695-4881-4/12 $26.00 © 2012 IEEE

DOI 10.1109/ICCECT.2012.97

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2012 International Conference on Control Engineering and Communication Technology

978-0-7695-4881-4/12 $26.00 © 2012 IEEE

DOI 10.1109/ICCECT.2012.97

755

The following is the main structure of the sensor. A plastic round pipe, there are some inlet wormholes in the pipe wall, the intine is smooth, and its bottom is a funnel. A plastic box connected with the top of the plastic round pipe, in which there is a battery module and a wireless sensing module. A glass round pipe connected with the bottom of the funnel, which is the channel the pests freely falling. A pair of mutually insulated detection electrodes is mounted on the outer wall of the glass round pipe. A plastic socket pipe with a conical head is connected with the bottom of the plastic round pipe, which forms a pest trap, inside of which is the pest feeding attractant. A capacitance detection circuit is fixed on the intine of the plastic socket pipe.

B. Design Principle The wireless sensor studied in this paper can

simultaneously detect the species and quantity of the grain pests, it mainly includes the two detection electrodes used to detect the species and quantity of grain pests, the capacitance detection circuit connected to the two detection electrodes, the wireless sensor module connected to the capacitance detection circuit, and the detection methods used to detect the species and quantity of grain pests. The principle[6] diagram of the sensor is shown in Figure 2.

Capacitance DetectionCircuit

Wireless SensingModule

C1C2

SCLSDAGNDVCC

INT

Figure 2. Principle Diagram for the Sensor

The two detection electrodes are two mutual insulated and peer-to-peer metal coupons fixed on the outside of the pest falling channel.

The capacitance detection circuit, of which the CIN and EXC pin is respectively connected with the poles of the pests detection electrodes by C1 and C2 wire, and connects with the wireless sensor module by the VCC, GND, INT, SDA, SCL wire. It detects the capacitance value continuously in ultra-low power.

The wireless sensing module[7] consists of a microcontroller and wireless radio frequency circuit, is powered by batteries, and supplies power to the capacitance detection circuit, and analyzes and processes the change range and the changing times of the capacitance value detected by the capacitance detection circuit, to determines the species and quantity of grain pests and record, and realizes the wireless transmission of data according to protocol.

The detection method of the species and quantity of grain pests is, the grain pests free falling between the detection

electrodes will cause the change of the capacitance detection electrodes, and different species of the grain pests corresponds to different capacitance value range, which can distinguish the species of grain pests. The changing times of capacitance value of the detection electrodes are used to count the quantity of grain pests.

C. Design of The Sensor The capacitance detection circuit mainly consists of the

capacitance detection chip AD7151 and some additional circuits. The AD7151 continuously and directly converts the capacitance value of the detection electrodes linked by the C1 and C2 wire into digital quantity. And it is linked with the wireless sensing module in the plastic box by five wires VCC, GND, INT, SCL and SDA, which are deployed in the wiring channel between the exine and the intine. The VCC is the power line, the GND is the ground wire, the INT is the alarm line when the capacitance value exceeds the early alarm value, and the SCL and SDA carry information between the devices connected to the I2C-bus. When pests enter the detection electrodes, the capacitance value is out of range, to notify the wireless sensor module by the INT wire. The wireless sensing module mainly consists of some additional circuits and the chip SI1000 which consists of a microcontroller and wireless radio frequency circuit, is powered by batteries, and supplies power to AD7151 by the VCC wire, and exchanges commands and data with the AD7151 by the SCL and SDA wire. The equivalent circuit of the sensor[8] is shown in Figure 3.

GND SDAVDD SCLNC NCCIN OUTNC EXC

VCCGNDSDASCLINT

12345

109876

12345

CAD7151

SI1000

C1

C2

Pests DetectionElectrodes

Capacitance Detection CircuitWireless

Sensing Module

Figure 3. Equivalent Circuit of The Sensor

III. APPLICATION OF THE SENSOR

We produce sensors in accordance with the design scheme, and insert everywhere in grain bulk. Because of being Induced by pest feeding attractant in the detection device, the grain pests free fall when go into the plastic round pipe from the inlet wormholes, and go through the pest channel and the pests detection electrodes, then the capacitance detection circuit can detect the capacitance of the electrodes, and determine the species of grain pests according to the change range of capacitance value, and then records the number of the interruptions caused by the capacitance change to determine the quantity of grain pests. The wireless sensor module transmits the wireless data to the convergent node according to the corresponding

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transmission protocol, then transmits to the host. The host analyses and processes the received data to determine the species and the quantity of grain pests, and decide to whether to alarm. Then the people decide whether to take measures for pest control on grain bulk, and kill the pests by the fumigation or other methods to ensure the safety of food storage. The working drawing of the sensor is shown in Figure 4.

SensorGrain Bulk

Figure 4. Working Drawing of The Sensor

IV. EXPERIMENTAL RESULTS

According to the design[9], the environmental conditions of this experiment is set, the power is 3.0V and 70µA, the temperature is 20 , The value of the setup register is 6, the value of the sensitivity register is 8, the sensitivity is 0.006252pF, the max capacitance value is 7.483236 pF, the min capacitance value is 7.358187pF the max-min capacitance value is 0.125049pF, and the max capacitance value-mean is 0.1323pF. The input capacitance and sample mean can be calculated from the output data using the following formula 1 ( Input_Range = 2pF ):

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After repeated experiments, the analysis of the experimental data is shown in Figure 5 and Figure 6.

Figure 5. The Changes of Multiple Parameters When The Pests Free Fell

Figure 6. The Capacitance Value - Mean of The Detection Electrodes

The changes of the capacitance when three species of the pests free fell into the channel is shown in Figure 5, each repeated three times tests, Figure 6 shows the changes of the capacitance value - mean, when the second species of pests free fell into the channel. The repeated experiments show that, when the pest falls into the detection electrodes, the interelectrode capacitance will change. According to the characteristics of capacitance, when the dielectric between the electrodes is different, the capacitance value will be different. Different species of the pests in grain bulk have different dielectric constant, then the change range of the capacitance value detected by the capacitance detection circuit is different, thus the species of the pests is determined. The quantity of grain pests is judged by the number of interrupts triggered by the change of capacitance value. The principle is: when no grain pests falls into the detection electrodes, the interelectrode capacitance value is equal to the alarm value, but when the grain pests falls into the detection electrodes, the interelectrode capacitance value will exceed the alarm value, that will trigger the OUT terminal of the AD7151 to send an interrupt signal to the INT terminal of the Si1000, then the battery starts to supply power, and the detection starts, obtains one or several capacitance values, then gets the average value, by the range of which judges the species of pests[10]. The quantity of grain pests are judged by the number of interrupt signal sent by the OUT terminal. One detection is completed, the sensor nodes will go to sleep. The repeated experiments show the impact of the environment on capacitance detection is very important. Therefore, when the outside temperature and humidity caused the change of capacitance value, we should adjust in a timely manner, otherwise the alarm value set in the system will be meaningless in the current environment. The change of the capacitance value caused by the grain pests falling is very little, as the figure shows, only a few hundredths of change, so the setting of the alarm value is particularly important. Relative to the current environment, if the alarm value is too low, then the grain pests falling won't be detected, and the current interelectrode capacitance be always in the overflow state. Then if the alarm value is too high, when the pests fall, or is not detected, or judging the

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range of the detected capacitance value is error. Therefore, when the outside environment is change, the alarm value should be adjusted in a timely manner, to get the correct quantity and species of the grain pests.

V. CONCLUSION

With the development of the technology, the sensor technology is increasingly used in the grain storage security. The long time application shows that this technology not only saves a lot of human and material resources, but also is accurate in measurement and efficient in work, plays a major role in grain security. After repeated experiments, the grain insect pest sensor designed in this paper not only can well detect the pests in grain, but also can determine the species and quantity of them, and has the advantages of low power and wireless transmission for the detection data, etc. The design scheme plays a great role in improving the sensor technology, it has the advantages of low cost, high precision and stable performance, and is suitable for mass production.

ACKNOWLEDGEMENTS

This work is supported by The Ministry of Science and Technology Fund of China (No.06c26211400735), The Multiparameter Grain Information Monitoring System Based on Wireless Sensor Network.

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