[雙語翻譯]單片機(jī)外文翻譯--基于單片機(jī)的低成本便攜式濕度計的設(shè)計與開發(fā)（英文）

1、IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE) e-ISSN: 2278-1676,p-ISSN: 2320-3331, Volume 10, Issue 3 Ver. IV (May – Jun. 2015), PP 50-56 www.iosrjournals.org DOI: 10.9790/1676-10345056

2、 www.iosrjournals.org 50 | Page Design and Development of Low Cost and Portable Microcontroller Based Hygrometer Kazi Golam Martuza1, Humayun Kabir1*,

3、Farhana Hafiz2, Fahmida Akter2, Mahbubul Hoq2, Mahedee Hasan1, Md. Abdul Mannan Chowdhury1, 1Department of Physics, Jahangirnagar University, Savar, Dhaka-1342, Bangladesh. 2Institute of Electronics (IE), AERE, Savar, Dh

4、aka, Bangladesh. 1*Address for correspondence: Humayun Kabir, Abstract: The hygrometer is widely used in air conditioner, humidity data logger, humidifier & dehumidifier etc. The aim of this research work is to de

5、sign and development of a low cost, portable microcontroller based hygrometer. The hygrometer has been designed using the sensor module HSM-20G. The sensor operates in capacitive principle, i.e. changes in relative hu

6、midity (RH) of the surrounding air cause a change in dielectric constant of the polymer film leading to a change of sensor capacitance. The module converts this capacitance change into analog voltage. The HSM-20G senso

7、r provides analog voltage for both temperature and humidity. The sensor is connected with PIC16F876A microcontroller, which converts the analog voltage into digital and display the result into 16 X 2 alphanumeric LCD d

8、isplay. The program is written in C language using mikro C PRO. The measuring accuracy of the humidity reading of our designed meter is negligible. Keywords: Hygrometer, microcontroller, relative humidity, sensor capa

9、citance, LCD display, and C program. I. Introduction Hygrometry is the part of physics, which deals with the measurement of the amount of water vapour present in a given volume of air. Condensation of this aqueous vapou

10、r present in the atmosphere is responsible for various phenomena like formation of clouds, fogs, rains, snows, hails, etc [1]. The capacity of air to hold water vapour is limited and is controlled by temperature only.

11、If the air in any place and time contains the maximum amount of water vapour that it can hold, it is said to be saturated, otherwise it is unsaturated [2]. Dew point is the temperature at which water vapour actually pr

12、esent in the air just reaches saturation. We may, therefore, define dew point as that temperature at which the pressure of water vapour actually present in the atmosphere is equal to the saturation pressure of water va

13、pour corresponding to dew point. Knowledge of dew point enables us to find out the pressure of water vapour actually present in the atmosphere. For example, dew point today is 20 at a particular place at the time of ob

14、servation. From Regnault?s chart, it is found that the saturation pressure of water vapour at 20 0C is 17 mm. Hence today at the particular place, the pressure of water vapour actually present in the atmosphere is 17 m

15、m [3]. The term ?humidity? signifies the dampness or wetness of the atmosphere due to its holding of water vapour. It is the concentration of water vapor in the air. The concentration can be expressed as absolute humidi

16、ty, specific humidity, or relative humidity [4]. Relative humidity (R.H.) or hygrometric state of air is defined to be the ratio of the quantity of water vapour actually present in a certain volume of air at a particula

17、r temperature to the quantity of water vapour that would be required to saturate the same volume of air at the same temperature [5]. So R.H.= Cat air ofvolume samethe saturateto necessary our water vap ofMassCat ai

18、r ofany volume in present actually our water vap ofMass00??Since pressure of water vapour is proportional to the amount of water vapour present in a given volume of atmosphere, we may define relative humidity as R.H.

19、= Cat air the saturateto necessary our water vap ofPressureCat air in the present actually our water vap ofPressure00??Since the saturation vapour pressure of water at dew point is the actual pressure of water vapo

20、ur contained in the atmosphere at a particular temperature, so relative humidity can be written as R.H.= airthe ofC)(retemperatu at thepressurevapour Saturationpointdewat thepressurevapour Saturation0 ?Design And Dev

21、elopment Of Low Cost And Portable Microcontroller Based Hygrometer DOI: 10.9790/1676-10345056 www.iosrjournals.org 52 | Page Fig. 1: Simplif

22、ied block diagram of the developed system. III. Design and Circuit Description 3.1 HSM-20G Humidity Sensor Module The module of HSM-20G is essential for those applications where the relative humidity can be converted to

23、 standard voltage output. Humidity sensor is device consisting of special plastic material whose characteristics change according to the amount of humidity in air. Basically, this sensor senses the amount of water vapo

24、r in air. For this research work, analogue input sensor we used. HSM-20G is essential for the objectives and applications where the reading in terms of relative humidity was converted into standard voltage output. The

25、applications include humidifiers and dehumidifiers, air conditioner, humidity data loggers and automotive climate control [9, 10]. Table-2 shows the specification of the HSM-20G humidity sensor. Table-2: The specificat

26、ion of the HSM-20G humidity sensor. Characteristics HSM-20G Input voltage range DC 5.0-0.2 V Output voltage range DC 1.0-3.0 V Measurement Accuracy 5%RH Operating current(Maximum) 2mA Operating RH range 20 to 95%(10

27、0%RH intermittent) Temperature range 0c to 50c Long term stability(typical drift per year) 1.5% Time response(63% step change) 1 min 3.2 Low voltage power supply Microcontroller and other electronic components, whic

28、h are used in designing humidity monitor, require a dc voltage (+5V). A regulated dc power supply is designed for this purpose. The complete circuit of a regulated dc power supply is shown in Fig-2 using a 7805 IC as a

29、voltage-regulating device. The power supply is a combination of three sections [11, 12], namely: bridge rectifier, a capacitor filter and IC voltage regulator. 3.1.1 Bridge rectifier: The bridge rectifier converts the s

30、tep-down transformer?s secondary ac voltage into pulsating dc voltage. 3.1.2. Capacitor filter: The pulsating dc voltage is applied to the capacitor filter. This filter circuit reduces the pulsations in the rectifier

31、dc output voltage and the output voltage is 9V. 3.1.3 IC voltage regulator: The IC voltage regulator provides regulated output and C2 is used to improve transient response. Although voltage regulators can be designed u

32、sing op-amp, it is quicker and easier to use IC voltage regulators [13, 14]. In this design a positive fixed voltage regulator L7805 is used. The voltage regulation curve for designed low voltage power supply is shown