Feasibility Study of Sensors on Tmote Sky for Wireless Sensor Network Applications

低耗能，低成本，體積小，可自我調適和允許訊號無線傳輸的無線感測網路是近年來通訊科技、微機電和積體電路迅速發展的產物，在應用上可發展成為建構智慧環境的工具。本研究旨在探討遵循ZigBee聯盟與IEEE 802.15.4通訊協定的無線感測網路相關產品Tmote Sky (Moteiv, USA) 上之PAR, TSR感測器 (S1087, S1087-01, Hamamatsu, Japan) 與溫/濕度感測器 (SHT 11, Sensirion AG, Switzerland) 之適用性。 本研究使用可攜式光譜量測儀器 (LI-1800, LICOR, USA)、標準溫度計 (Tomei, Japan) 和飽和鹽溶液來驗證Tmote Sky所量測到的PAR與TSR光量、溫度與相對濕度，後二項並與環境量測研究常用的HOBO溫濕度記錄器 (Onset, USA) 的量測結果比較。 研究結果發現在不同光源與光量的條件下，Tmote Sky較適合量測室內一般照明或LED光盤的光量；在室外中等亮度或更高的光量下，此兩顆光感測器均無法提供可接受的精度。改善方式或許可在光感測器上方安裝已知穿透率的透明材料，讓感測器的輸出電流在4 μA內，由此轉換求得的光量，再除以該穿透率，求出真正的光量。 Tmote Sky的溫度感測器與標準溫度計比較有3 ~ 4 ℃的誤差；九種飽和鹽溶液所提供的標準相對濕度範圍為11.30 ~ 93.58 %，在25 ℃與標準相對濕度範圍內，Tmote Sky的濕度感測器的誤差為8 ~ -26 %，高濕與低濕範圍的誤差較大。Moteiv公司將光感測器與溫/濕度感測器並排的設計並不適當，在光線直射下，量光量時，溫/濕度讀值會受到很大的影響，在晴天時溫/濕度與HOBO比較可分別相差達16.3 ℃和17.4 %；量溫濕度時，需要遮蔭與適度通風，在應用上需要在光感測器上加裝導光設備，或者光和溫/濕度感測器應分開排放且後者應有適度遮蔽與通風。Wireless sensor network (WSN) becomes popular due to the rapid development of IT, MEMS and IC technology. Features such as low electricity consumption, low cost, small size, self-adjustable and capable of wireless communication make it a good tool to develop ambient intelligent system. The objective of this research is to investigate on PAR and TSR light sensors (S1087, S1087-01, Hamamatsu, Japan) and temperature (T) /relative humidity (RH) sensors (SHT 11, Sensirion AG, Switzerland) on Tmote Sky, which is a commercially available ZigBee based (following IEEE 802.15.4 protocol) WSN related product of Moteiv company of US. Portable spectroradiometer (LI-1800, LICOR, USA), standard thermometer (Tomei, Japan) and saturated solutions of 9 types of salt were used as standards to validate the data measured by PAR, TSR, T and RH sensors of Tmote Sky. Latter 2 were also validated with HOBO T/RH data logger, which is popular in environmental measurement. Results of light measurements shows Tmote Sky is quite accurate when measuring indoor light or LED panels used. However, for outdoor solar radiation measurement, the sensors fail to provide accurate readings. Some improvements such as a transparent film with the given transmittance need to be used to constraint sensor output current below 4 μA. Results of Temperature measurement show 3 to 4 degree C difference. Under 25 degree C and 11.30~93.58 % RH range provided by saturated solution of 9 types of salt, the error of RH sensor on Tmote Sky range from 8 to -26 %. The arrangement of PAR, TSR light sensors and T/RH sensors closely connected is a poor design. Light measurement requires direct impact of light beam and this will affect accuracy of T/RH sensors. In a sunny day, the error can be as large as 16.3 degree C and 17.4% RH. When measuring T and RH, prevent direct radiation is needed thus light sensors with certain light guide is needed to provide accurate readings.誌謝 i 摘要 ii Abstract iv 目錄 vi 圖目錄 viii 表目錄 xiii 第一章 前言 1 1-1 研究緣起 1 1-2 研究目的 1 第二章 文獻探討 2 2-1 光、溫度和濕度對植物的影響 2 2-1-1 光 2 2-1-2 溫度 5 2-1-3 濕度 6 2-2 感測器 8 2-2-1光感測器 8 2-2-2 溫度感測器 11 2-2-3 濕度感測器 14 2-3 無線感測技術 16 2-3-1 田間伺服器 16 2-3-2 無線感測網路 19 第三章 材料與方法 20 3-1 研究設備 20 3-1-1光譜量測儀 20 3-1-2 LED光盤 21 3-1-3 溫濕度記錄器 24 3-1-4 低溫培養箱 25 3-1-5 Tmote Sky 26 3-1-6 PL燈管 27 3-1-7 標準溫度計 27 3-1-8 應用軟體 28 3-2 研究方法 29 3-2-1 Tmote Sky的光感測器之檢驗 29 3-2-2 Tmote Sky的溫濕度感測器之檢驗 29 第四章 結果與討論 33 4-1 LED光盤控制器之亮度設定與實際光量關係 33 4-2 Tmote Sky之光感測器的光照電流vs.實際光量 36 4-2-1 以LED光盤為光源 36 4-2-2 以PL燈管為光源 46 4-2-3 以太陽為光源 48 4-3 Tmote Sky與HOBO量測溫濕度的比較 52 4-3-1 溫濕度量測的準確性 52 4-3-2 空氣流動的影響與差異性比較 55 4-3-3 有無遮蔭的影響與差異性比較 59 4-4 討論 71 第五章 結論與建議 76 參考文獻 7