智慧型水族箱高精度溫度控制系統

Abstract

中文摘要 本專題之目的在於解決傳統水族箱因缺乏精準、雙向恆溫防護而在夏季熱浪時導致魚隻生理崩潰致死的痛點，期望透過純硬體的電路設計，為水族生態建構一套高穩定、高精確度的雙向恆溫調控系統。 在過程及方法上，採用三線式結構的 Pt100 鉑熱電阻作為核心感測元件，並且，將其置於由運算放大器 OP07 與 TL431 精密基準電壓源所建構的「有源電橋」反相回授路徑中，把 0°C 至 50°C 的動態水溫線性化轉為 0 mV 至-19.25 mV 的微弱直流負電壓；隨後，後級反相放大器提供 103 倍的增益，將訊號翻轉並放大至正直流電壓。在控制與指示端，將系統跨接一組高輸入阻抗的數位電壓表頭進行直觀顯示，並利用 LM393 電壓比較器 打造硬體控制迴路，當水溫超標時，驅動大功率 MOSFET 啟動致冷晶片降溫，而水溫過低時則透過繼電器導通 PTC 陶瓷加熱棒。 最終結果顯示，經標準電阻箱之逼近法調校與五點線性度對比測試，本系統消除傳統惠斯通電橋的非線性死區，控制死區在 0.5°C 內，且 MOSFET 開關元件導通功耗極低。此高可靠度、免除微處理器當機風險的控制技術，不僅可以應用於家用或工業級精緻水族養殖、高密度水產繁養殖場等環境，亦可延伸推廣至需要高穩定直流弱訊號調理及嚴格控溫的精密化學實驗室液體恆溫、生醫檢體保存箱或環境監測設備中。

Abstract The purpose of this project is to address the problem of fish dying from physiological breakdown during summer heat waves in traditional aquariums due to the lack of precise, two-way temperature control. The aim is to construct a highly stable and accurate two-way temperature control system for aquarium ecosystems through pure hardware circuit design. In terms of process and methodology, a three-wire Pt100 platinum resistance thermometer is used as the core sensing element. This thermometer is placed in an inverting feedback path of an "active bridge" constructed from a precision operational amplifier OP07CP and a TL431 precision reference voltage source. This linearizes the dynamic water temperature from 0°C to 50°C into a weak DC negative voltage ranging from 0 mV to -19.25 mV. Subsequently, a post-stage inverting amplifier provides a gain of 103.9 times, inverting and amplifying the signal to a positive DC voltage. At the control and indication end, the system uses a high-input-impedance digital voltmeter for intuitive display and an LM393 dual voltage comparator to create a hardware window control loop. When the water temperature exceeds the limit, a high-power MOSFET is driven to activate the cooling chip for cooling; when the water temperature is too low, a relay activates the PTC ceramic heater. Final results show that, after calibration using a standard resistance box approximation method and a five-point linearity comparison test, this system eliminates the nonlinear dead zone of traditional Wheatstone bridges, keeping the control dead zone within 0.5°C, and exhibiting extremely low power consumption of the MOSFET switching elements. This highly reliable control technology, eliminating the risk of microprocessor crashes, is perfectly applicable not only to home or industrial-grade aquariums and high-density aquaculture farms, but can also be extended to precision chemical laboratory liquid temperature control, biomedical specimen preservation chambers, or environmental monitoring equipment requiring highly stable DC weak signal conditioning and strict temperature control.