Remote monitoring RH&T using sensor and PIC MCU over Zigbee
Contents
1. Fig 10 Report from the database measured temperature in the period of time Quality Record Monitoring is the systematic and regular collection of a measurement During the planning phase the user e g manufacturer should define what when and how data should be monitored the monitoring of data may be continuous or periodic depending on the user requirements Measurement data may be retained as a quality record see Fig 10 in a form that is retrievable suitable for analysis and meets both QMS and regulatory PRZEGLAD ELEKTROTECHNICZNY ISSN 0033 2097 R 90 NR 9 2014 requirements The RH amp I monitoring data should be recorded and available for review to assess whether the required storage conditions have been met Described GUI may be modified and upgraded easily by adding custom fields or adding new features in accordance with user requirements Conclusion Measurement and monitoring of temperature and relative humidity finds applications in numerous areas The use of smart sensors which have both temperature and humidity sensors with calibration and communication interface all built inside them simplifies the design and implementation and reduces the overall cost The experimental results show that the realized system implements safe and convenient remote monitoring of the environment in warehouse and has high availability and reliability The implemented database stores the data collected by sensor enabling the l2. measured once per interval This interval can be changed by selecting the desired value from the slider labeled as Interval by dragging on it The user can define a location and appropriate max min limit value for temperature and humidity inside group Alarmne granice so as to differentiate between the locations and conditions for alert These information will be recorded in database When the measurement process is active starting and stopping of the measurement process can be done using Start and Stop buttons the user is able to see the current RH amp I data coming from the sensor in the corresponding fields If program detects relative humidity or temperature outside near the acceptable ranges alerts will 168 PRZEGLAD ELEKTROTECHNICZNY ISSN 0033 2097 R 90 NR 9 2014 be displayed on the GUI through the change in the background color red yellow of these corresponding fields after which a long beeps will sound Also on the GUI is illustrated air parameter RH amp T flow in the form of an easy to read graphs as can be seen in Fig 8 Aside from the user being able to view continuously updated data on the GUI the system has other features and functionalities on the menu strip there are different drop down menus named File Port PAN etc Using PAN menu or PAN group options on the GUI for example it s possible to view and pre configure XBee parameters with AT commands List of all AT commands available from Help me
3. to write compile and debugging of the programs and PICBootloader software to burn hex file onto the flash memory of the microcontroller 12 The PIC will then begin executing the program immediately upon power up Here described Microcontroller Support Circuitry may be used alone for monitoring RH amp T user interface realized using four buttons on the PCB mentioned before and can be used as a transmission module to send the measured data using ZigBee wireless link ZigBee wireless link The wireless remote monitoring system has more and more application and here a remote monitoring system based on ZigBee is presented ZigBee is a wireless communications protocol is built upon the IEEE802 15 4 standard standard defines robust radio PHY physical and MAC medium access control layers ZigBee defines the network layer specifications and provides a framework for application programming in the application layer It is designed for low speed 20 250kb s low cost communication between two or more devices making it ideal for many applications In this system ZigBee network point to point topology is a medium for data transfer between GUI running on host PC and MCU board Here used the XBee RS 232 Adapters with XBee PRO RF modules shown in Fig 6 provides wireless connectivity to any RS 232 serial device Unlike an embedded wireless module which requires design integration and development time these off the shelf adapters p
4. 6 March 2010 13 Olivera Jankovic GUI interface as support the integration of ZigBee Networks nternational Symposium INFOTEH JAHORINA Vol 11 p 1134 1139 March 2012 14 JChampion A flexible charting library for NET Jun 2007 Product R F Stapelberg Prasad Identification of Critical Criteria of On line 2008 Vol 1 User documentation Authors Mr in Olivera Jankovic Air Depot ORAO str Sabackih daka bb 76300 Bijeljina Bosnia and Herzegovina E mail janoljla yahoo com Dipl in Ratko Jankovi Ci ak d d metal and machine building industry Rodoc bb 88000 Mostar Bosnia and Herzegovina E mail jratko yahoo com 169
5. Olivera JANKOVIC Ratko JANKOVIC AIR DEPOT ORAO Bosnia and Herzegovina 1 CICAK Bosnia and Herzegovina 2 Remote monitoring RH amp T using sensor and PIC MCU over Zigbee Abstract This article describes realized system for remote monitoring relative humidity amp temperature RHT using accurate SHT21 sensor and PIC MCU over ZigBee PIC MCU is programmed to communicate using 12C interface with this sensor and display the information on a character LCD Using XBeeRS 232 Adapters XBeePRO RF Modules provides wireless link to remote PC s GUI which was realized using C amp ZedGraph The system can be used in many applications for RH amp T monitoring especially where high precision and long term stability is required Streszczenie W artykule opisano system zdalnej kontroli temperatury wilgotno ci Do tej kontroli u yto czujnika SHT21 oraz oprogramowania PIC MCU Ca y system przesy a dane do zewn trznego komputera za po rednictwem interfejsu Zigbee Zdalne monitorowanie wilgotno ci i temperatury z wykorzystaniem interfejsu Zigbee Keywords Remote monitoring system sensor microcontroller ZigBee network S owa kluczowe zdalne monitorowanie pomiar temperatury i wilgotno ci Zigbee doi 10 12915 pe 2014 09 42 Introduction Temperature and relative humidity are two very important ambient parameters that are directly related to human comfort On the other hand to avoid damage of products or to achieve proper proce
6. digital processing unit Every sensor is individually calibrated and tested and provides calibrated linearized signals in digital I2C Inter Integrated Circuit C format The sensor is connected with control circuit board via the I2C_ serial digital interface This mode is especially appropriate in case like this when the integrated circuit and microcontroller which the integrated circuit should exchange data with are within the same device The realized system for monitoring is composed of custom designed PCB printed circuit board built around the PIC16F877 microcontroller PIC microcontroller is programmed to communicate using I2C interface with these sensor read the temperature and relative humidity data and display the information on a character LCD The circuit board can be controlled remotely from a PC through an GUI application that is running on the PC via RS232 port using ZigBee wireless technology see Fig 1 ZigBee is a universal wireless language connecting radically dissimilar devices to work together and enhance everyday life ZigBee standard 2 is mainly for wireless sensor networks like Bluetooth is for short distance communications and Wi Fi is for internet ZigBee Alliance provides a simple low cost and low power wireless control standard for remote monitoring and controlling based on IEEE 802 15 4 the standard for low data rate wireless personal area networks WPANs As part of Digi s drop in networking pro
7. duct family Digi XBee with ZigBee adapters can be used 3 in virtually any location where conditions are extreme including industrial applications where it can be used both for monitoring and control In this case Digi s XBee RS 232 adapters based on XBee PRO RF modules are used to enable existing devices for ZigBee connectivity 4 5 end to end device networks without the need for a wired network infrastructure An indoor outdoor range for XBee PRO devices is 90 m 1600 m PC application in the form of a GUI Graphical User Interface is created and then used to set appropriate input control parameters and for monitoring RH amp T data from sensor This user software is realized using C amp ZedGraph for graph plotting and enables data acquisition various data analysis and data presentations 6 In industrial plants large amounts of data must be recorded during production storage products and quality certificates for QMS Quality Management System etc Due to portability and simple wireless setup realized system of wireless monitoring amp measurement of RH amp T automates documentation QMS records etc of these data and performs appropriate alarm if limit values are close to or exceeded e g yellow alarm or red alarm The system shown in Fig 5 is realized in accordance with user requirements of i ak metal and machine building industry in Mostar Quality and accuracy of the described system is acknowledged by seve
8. e End Device and the Coordinator talk to each other Fig 7 System Data Flow Diagram in a UART interfaced environment GUI A graphical user interface or GUI is a type of user interface which allows people comfortable way to interact with a computer and computer controlled devices 13 The Wi RH amp T user friendly graphical interface was developed to display current time stamped information about air conditions such as temperature and relative humidity GUI is programmed in the C language MS Visual C 2010 Express Edition and ZedGraph 14 was used for chart plotting and MS Access database for storing data ZedGraph is a set of classes written in C that provide a high degree of flexibility for creating 2D line and bar graphs of arbitrary datasets When the user starts the Wi RH amp T program the first step is to connect with the XBee modul using COM port The desired port and parameters used during serial communication baud rate stop bits etc should be selected from appropriate a pull down lists located inside group Port in the upper right corner of the Wi RH amp T window When the port is opened pressing button Otvori port the main GUI functions are enabled p taka Gie ien Ha teg yeah Lry oes mjeene wrijedn el relate viagriosti TF FR Fig 8 GUI view at the online acquisition mode with RH amp T graphs The parameters temperature and humidity are
9. ed into 5 ports Port A Port E which can be configured in various ways to communicate with many different peripheral devices Many of these pins are multiplexed with more than one function Each port has an associated PORTX register bi directional port and a TRISx register data direction register Setting a bit in the TRISx register makes the corresponding pin an input clearing the bit makes it an output Here PIC16F877 microcontroller is connected to HD44780 LCD in 8 bit data interface eight bus lines DO to D7 are used for data transfer as it is presented in Fig 3 LCD Device uses PORTD RDO RD7 Data Lines and PORTE REO RE2 Control Lines RS RW and E When RS pin is low RS 0 instruction register is selected information on data bus is taken as commands When RS pin is high RS 1 data register is selected and information on data bus is taken as ASCII value of respective character to be displayed on HD44780 LCD To add SHT21 sensor SMD surface mount technology type sensor chip is mounted to custom developed small mini PCB that uses the standard I2C bus for control and data transfer Recommended supply voltage VDD of SHT21 is 3 0V range of 2 1 3 6V and power supply pins VDD and VSS Ground must be decoupled with a 100nF capacitor that shall be placed as close to the sensor as possible Typical application circuit see Fig 4 includes pull up resistors for both SDA Serial Data and SCK Serial Clock lines For s
10. high After sending the Start condition the subsequent I2C header consists of I2C address and an SDA read write direction bit for writing the first I2C byte will be 0x80 for reading 0x81 The sensor indicates the proper reception of a byte by ACK bit After the issue of a measurement command OxE3 for temperature temperature sensor output Sr OxE5 for relative humidity relative humidity sensor output Sry the MCU must wait for the measurement to be completed Measured data are transferred in two byte package MSB LSB and with relative humidity signal output Sru the relative humidity RH Humidity Range 0 to 100 RH is obtained by the following formula 1 and result is in RH S 1 RH 6 125 516 The temperature T Operating Temp Range 40 C to 125 C is calculated by inserting temperature signal output Sz into formula 2 and result is in C 2 T 46 85 175 7222 2 For measurement is used the highest resolution 12 bit for RH and 14 bit for T but in both formulas for computing no matter which resolution is chosen Relative humidity reading strongly depends on temperature In case of testing or qualification the reference sensor and test sensor must show equal temperature to allow for comparing humidity readings For implementations of the firmware programs code programmed into the microcontroller on the previously designed hardware modules is used MPLAB IDE 11 MPLAB IDE and HI TECH C are used
11. nu EE Scatter graf Relativna vla nost vs Temperatura Baza podataka Naslovi Podaci Ovdje kopirajte paste podatke selektovane iz baze podataka Crtaj graf J Relativna vla nost 8 824 6 4 Fig 9 Offline mode The data set includes a set of pairs of values temperature RH and this is ideal for the use of a Scatter chart The Grafovi feature provides 2D plotting facilities in offline mode provides user with ability to zoom resize and print graph too In this mode the whole drawing points must be provided copying from database using menu named Baza podataka to appropriate text box and the user can provided through menu item Naslovi give titles and axis labels and a legend for chart see Fig 9 For example user can plot the variation of relative humidity with temperature In these situations there are two parameters where one depends on another for every temperature value in centigrade there will be a corresponding value of relative humidity The data set includes a set of such pairs of values temperature RH and this is ideal for the use of a Scatter chart The chart as shown in Fig 9 has temperature along the horizontal axis and relative humidity along the vertical axis lewjoilaj mperonja za diadani dan i poriod vremena dna 153 2002 of 140OO S d ued Dpi Procura iori borgne i tebrer labeari OG jengah Lobe ga meraya EEE AAA P Baier poid ve orem
12. ocal management of environmental data Due to portability and easy installation the system can be used both for long and short term monitoring The developed printed circuit board allows adding additional sensors for monitoring other air parameters e g carbon dioxide and realized GUI allows easy upgrade REFERENCES 1 SHT21 datasheet Sensirion Switzerland Ver 3 December 2011 2 ZigBee Specification ZigBee Alliance document 053474r17 January 2008 3 Olivera Jankovic Monitoring data from the sensor in the drop in network concept 56th ETRAN Conference Zlatibor presented paper June 2012 4 XBee XBee PRO RF Modules 802 15 4 v1 xEx Manual Digi International 2009 5 Olivera Jankovic Using XBee OEM Modules for the implementation of the ZigBee Network International Symposium INFOTEH JAHORINA Vol 11 p 1066 1070 March 2012 6 Wiliem D Hargreaves K D V Yarlagadda Data Acquisition system A JSTPME journal No 2 pp 11 15 7 EAGLE User Language ver 10 0 CadSoft 2010 8 Robot Platform PCB Etching Using Toner Transfer Method Feb 2012 9 PIC16F877XA datasheet Microchip Technology Inc 2003 10 Easy PIC Development Board User Manual Microchip Technology Inc 1st Edition April 2005 11 MPLAB IDE Quick Start Guide Microchip Technology Inc 2006 12 Olivera Jankovic Using MPLAB IDE with PICDEM Z Development Platform International Symposium INFOTEH JAHORINA Vol 9 Ref E V 19 p 782 78
13. oldering SHT21 standard reflow soldering is used but it is important that after soldering the devices should be stored at ambient conditions gt 40 RH during more than 5 days to allow the sensor element to re hydrate 166 PRZEGLAD ELEKTROTECHNICZNY ISSN 0033 2097 R 90 NR 9 2014 Fig 3 Printed circuit board schematic SHT21 SHT21D communicates with I2C protocol that allows communication of data between I2C devices over two wires The I2C protocol defines the concept of master the device that is in charge of the bus at the present time and slave simply listen to the bus devices It sends information serially using one line for data SDA and one for clock SCL Fig 4 Typical application circuit including pull up resistors Rp e g 10kQ and decoupling of VDD and VSS by a capacitor There are two modes to communicate with the SHT21 sensor hold master used in this case or no hold master mode In the first case SCL line is blocked and SHT21 keeps the bus busy until measurement is finished No hold master mode allows processing of other 12C communication tasks on bus while the sensor is measuring By default sensors have the same I2C address set during production It is I2C 7 bit device address equal 1000 000 0x40 Each transmission sequence begins with Start condition a high to low transition on the SDA line while SCL is high and ends with Stop condition a low to high transition on the SDA line while SCL is
14. ral tests and user satisfaction PRZEGLAD ELEKTROTECHNICZNY ISSN 0033 2097 R 90 NR 9 2014 165 Fig 1 The implemented system overview Microcontroller Support Circuitry The system that is used for monitoring relative humidity and temperature is based on custom designed and developed printed circuit board see Fig 2 a compact controller board based on the Microchip technologies The PCB is designed in a modular manner The schematic shown in Fig 3 and board layout diagrams have been created using the Eagle Easily Applicable Graphical Layout Editor Version 5 10 0 for Windows PCB design tool 7 and it was used laser printer transfer method of board etching 8 The PCB supports RS 232 communication with a PC SPI and I2C busses for communicating with other chips PCB supports Parallel Slave Port communication four analog input 0 5V and standard 5V CMOS digital I O for anything else Real Time Clock RTC and calendar PFC8583P with battery supply is used to keep track of the current time even when the MCU is off Additional features of the PCB is bootloader A bootloader is a small program running in the microcontroller which is to be programmed and bootloader needs to be the first thing which is running after device reset This program allows downloading new firmware to the microcontroller via RS232 serial interface and to develop and load new code to the PIC without use of device called programmer Together with a relati
15. rovide instant wireless connectivity to existing RS 232 serial devices Quite often wireless modules are used as a bridge between a computer and a microcontroller or sensor PRZEGLAD ELEKTROTECHNICZNY ISSN 0033 2097 R 90 NR 9 2014 167 Fig 5 Photograph of the implemented system The XBee PRO RF modules were engineered to operate within the ZigBee protocol and support the unique needs of low cost low power wireless networks The XBee PRO RF modules operate within the ISM 2 4 GHz and interface to a host device through a logic level asynchronous serial port Through its serial port the module can communicate with any logic and voltage compatible UART as shown in Fig 7 Serial communications depend on the two UARTs_ the microcontroller s PC s and the RF module s are to be configured with compatible settings baud rate parity start bits stop bits etc Fig 6 Photograph of the XBee PRO ZB RS 232 Adapter inside and outside with external antenna The pre condition for the XBee modules to perform firmware updates and_ to configure the modules is to be connected to a computer Using free Digi s X CTU configuration software one module is configured as Coordinator each network requires one and only one coordinator and the other as End Device Personal area network identifier must be a unique and the same e g PAN ID 3333 for both modules and network addresses short 16 bits long 64 bits have to match This ensures that th
16. ss conditions it is often important to keep the environment and the indoor climate within certain temperature and humidity limits Low relative humidity may dry up the product or high relative humidity can cause significant sometimes irreparable damage to sensitive equipment supplies and products There is a recommended value for relative humidity amp temperature minimum and maximum acceptance limit for RH amp T in production and process environments like libraries breweries storages inside medical and other warehouses Temperature and humidity specifications need to be based on the needs for the raw materials finished products that you are storing in the warehouse In case there are no other requests one possible solution is to read the labels on things you store to determine the storage conditions required and to base your warehouse specifications on these Remote monitoring and data acquisition begins with the physical property or physical phenomenon which is to be measured and monitored Sensors are the devices which generate the data for the system to acquire In this example was used SHT21 acurate humidity and temperature sensor sensing accuracy 2 of Sensirion 1 which is to set new standards in terms of size 3x3mm and intelligence SHT21 features a generation 4C CMOSens chip Besides the capacitive relative humidity sensor and the band gap temperature sensor the chip contains an amplifier AD converter OTP memory and
17. vely powerful processor and I O capability the PCB allows multi purpose using and the wide range of projects and applications Fig 2 Photograph of the PCB with SHT21 sensor For higher level connectivity the board has RS232 DB9 connector power switch and there are very useful four user buttons on the board which may be programmed using polling or interrupt service routine In order to present the system output standard two line LCD 2x16 characters with backlight is placed on the board where the output from the RH amp T sensor displaying both the temperature and humidity level on the screen see Fig 2 The humidity level is shown as of RH relative humidity while temperature as unit of C degree of Celsius The PIC16F877 9 10 is the heart of the PCB containing the central processing unit of the board The PIC16F877 is 8 bit microcontroller based on reduced instruction set computer RISC architecture with only 35 instructions It features all the components which modern microcontrollers normally have For its low price high quality and easy availability it is a good solution in applications such as measurement of different values machine control devices the control of different processes in industry etc The PIC has a flash type program memory up to 8K x 14 words of FLASH Program Memory which can be written erased and rewritten chip can be reprogrammed up to 100 000 times The PIC16F877 has 33 I O pins divid
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