International Journal of Applied Engineering Research ISSN 0973-4562 Volume 9, Number 24 (2014) pp. 30187-30197 © Research India Publications http://www.ripublication.com
Implementation of Wireless Data Logger to Monitor Energy in Industries N.Suresh Assistant Professor, Dept of EIE, Sathyabama Universiy, Chennai-600119. Email:
[email protected] Mobile:9884785587
Abstract Energy is a scarce commodity. The gap between the supply and the demand of the electrical energy keeps on widening for developing countries. The cost of generating and transmitting the electrical energy increases rapidly due to depleting resources. This leads to the development of energy management system to reduce the consumption or optimal usage of energy in domestic and industries. Energy monitoring is one of the energy management techniques by which optimal usage of energy reducing the wastage can be ensured. The paper proposes a methodology to monitor electrical energy parameters such as energy, active power, reactive power, voltage, current,, power factor and frequency of the machines in a industry through microcontroller based wireless data logger utilizing RF technology.. Energy consumption of the machines in industries may increase or decrease depending upon the load condition. Hence, energy monitoring of such machines is necessary. Energy information about the machines is sent wirelessly and real time monitoring of the data of all the machines of the industry in personal computer is accomplished to check for any abnormality. The energy information about the machines are also stored in the data logger for every say, 5 seconds with date and time for later analysis. The method offers simple construction, reliable operation and low cost. Key Words: Data Logger, Energy management system, RF technology. Energy monitoring.
Introduction Energy monitoring is one of the energy management techniques by which an industry can make record of energy usage of the plant under various load conditions, collect information regarding the operation of the machines, managing the load, capturing the disturbances, obtaining load switching information, monitoring equipment reliability, optimal allocation of resources without wastage conserving the energy improved cost
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allocation, etc [1] Fault tolerant system can be designed based on real-time monitoring of the variation in the energy consumption of equipments.[2]. Data logger can be used to display data in real-time and can store it for later references. In [3] data loggers were used to display and store the temperature utilizing RFID. The drawback of this method is it does not talk about wireless range. Local Area Network based energy monitoring system was developed [4]. Carrying data from all the machines to the central location for monitoring through wires adds to the cost or difficult to implement in large industries. Web based real-time monitoring of power parameters was implemented [5].Internet access becomes the problem in case of malfunction in communication lines. Power plant energy monitoring system based on zigbee technology was proposed [6] . It surprisingly discussed only the zigbee technology whereas it does not give any information about the power parameters monitored and the communication range. Microcontroller based programmable underwater telemetry system were implemented in [7] to monitor human cardiovascular activity. In [8] temperature wireless data logger to observe the dental retainer with ultra-low power consumption is presented. A microcontroller based data logger was designed to measure the galvanic skin response data and it is relayed in the computer [9]. Energy management system in the mineral processing plant was implemented with PLC and the information is displayed on the personal computer using TCP/IP protocol [10]. It was a wired system. Energy monitoring system in residential environment of many dwellings were implemented and tested with wireless local area network[11]. Programmable Logic Device based data logger with MMC card to record ECG signal was developed[12] Bi-directional telemetry system has been implemented to send neurological signal [13]. Network architecture with Dispersed Tone Power Line Communication was developed for Home Energy Management System[14]. HEMS with zigbee technology was presented in [15,16]. Automatic gas monitoring system based on energy management system was implemented in [17]. From the literature it is clear that wireless technology has been widely used to monitor physiological parameters and monitor energy in home, whereas energy monitoring systems for industries are not designed A common drawback is their portability due to the need for wire connection to computer for operation and resulting wire tangling, prone to noises like EMI, Lightning, cannot be used at remote places and finally the cost and maintenance is very high which restricts the scope and applicability This paper proposes a methodology to monitor electrical energy parameters of machines in industries wirelessly and the data can be recorded for future analysis.
Wireless Energy Monitoring System Electrical parameters are frequently used in various energy management studies for effective utilization and conservation of energy. The proposed system acquires the energy information through data logger and transmits it wirelessly using RF transceiver. At the other end one more transceiver receives the data and stores it in the PC. The basic block diagram of the system is shown in fig.1.
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EN – Energy Node Figure 1: Basic block diagram of energy monitoring system. The hardware part mainly consist of the following components Data logger RF transceivers Energy nodes PC The functions, selection criteria , etc for these components are briefly discussed in the following sections. Data logger Data loggers are battery-operated, standalone measurement tools containing a microcontroller, memory, and sensors for measuring and recording one or more variables over time. They are typically quite small, enabling them to be deployed almost anywhere throughout a building, with some packaged to work in outdoor or more hostile industrial environments. The loggers operate unattended for hours, days, or months at a time. The block diagram of the data logger is shown in the fig.2. The microcontroller can be interfaced to the personal computer using the optional USB interface at the Energy station side for monitoring the energy. Keypad can be used for manual settings and adjustments. Real time clock is used to make record of the timings at which the data is sent. The data logger is designed in such a way that it meets the measurement accuracy, cost, ease of use, technical support, data readout, environment, flexibility.etc.
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Figure 2: Block diagram of data logging system Microcontroller The microcontroller is interfaced to energy nodes via RS485 network. The SD card, RTC, keypad also forms part of the data logger. The microcontroller used is of 8051 type which is selected based on the key features; High-speed Architecture (standard and X2 mode) SPI Interface (Master/Slave Mode) Full-duplex Enhanced UART with dedicated internal Baud Rate Generator 8-bit Clock Prescaler Keyboard Interrupt Interface Hardware Watchdog Timer Power Control Modes: Idle Mode, Power- down mode Microcontroller with high speed of operation is well suited. RISC architecture microcontrollers offer better speed, but based on the availability of software and as an introductory testing we have used 8051 series. The selected microcontroller speed of operation should match the RF transceiver, otherwise synchronization problem will occur. So the clock prescaler is necessary to adjust different frequency settings for the selected microcontroller. The microcontroller with USB interface and Keyboard interface facilitates easy interface to PC and keypad The microcontroller can be interfaced to PC using Max232 IC or USB transceiver IC. Power control modes are essential for the microcontroller. Since we rely upon the battery, the microcontroller must enter into sleep mode when not collecting data. Memory card There are different types of memory cards viz PCMCIA (Personal Computer Memory Card international Association), CF(Compact Flash), SM( Smart Media), MS( Memory Stick), xD(eXtreme Digital), SD (Secure Digital), MMC(Multi Media Card) etc. Most of the above mention cards have the memory capacity greater than 8 GB. So, the memory card is selected mainly on the complexity of the number of pins which can be used to interface it with the microcontroller. Flash memory cards (non-volatile memory cards that can be electrically erased and reprogrammed) are suitable for this purpose, because they offer high re-record-ability,
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power-free storage, high data storage rate and rugged environmental specifications Nowadays SD cards up to 8 GB capacity are available and the specifications are drawn for the cards up to 32 GB (high capacity cards). They come with a 9-pin edge connector and connect to the host controller via 4-bit parallel SD (secure digital) interface or SPI (serial port interface). For our application SD card with the memory capacity of 8GB is enough and it is interfaced to microcontroller through SPI. Energy Nodes The energy nodes are connected to various loads in the industries whose energy information is to be monitored. These nodes displays voltage, current, power, power factor etc. Data logger is interfaced to energy nodes through the RS485 network. The reasons for using RS485 is that up to 32 units can be connected to a maximum of 1200 meters distance with the data transfer rate of 10 Mbps. Whereas with the conventional RS232 network we can connect only two devices with the distance limit of 100 meters. Also the speed is less providing only 20kbps. The distance covered becomes a major factor since the loads are wide spread throughout the industries. A brief comparison of various network port is shown in the table 1. Communication can be established using the Modbus protocol. Modbus Protocol is a messaging structure developed by Modicon used to establish master-slave/clientserver communication between intelligent devices. Modbus is a de facto standard, truly open and the most widely used network protocol in the industrial manufacturing environment. Table 1: Comparison of Interfaces Interface Format
Maximum no. of devices
Speed bits/sec
2 32 unit loads
Maximum Length (feet) 50-1000 4000
RS232 RS485
Asynchronous Serial Asynchronous serial
USB
Asynchronous serial
127
16
12M
Figure 3: Modbus protocol master & slave
20K 10M
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Communication on a Modbus Network is initiated (started) by a “Master” with a “query” to a “Slave”. The “Slave “which is constantly monitoring the network for “Queries” will recognize only the “Queries” addressed to it and will respond either by performing an action (setting a value for example) or by returning a “response”. Only the Master can initiate a query. In the MODBUS protocol the master can address individual slaves, or, using a special “Broadcast” address, can initiate a broadcast message to all slaves. The modbus protocol schematic is shown in fig.3. The device address is the address of the slave to communication. The commands are issued to the slave by means of the function code. RF transceiver The RF transceivers are chosen based on the following criteria Data transfer rate Data transmission frequency Output power (dbm) Transmission distance covered Noise tolerance capability etc. Power consumption, power down modes. Generally the transmission frequency selected should lie in ISM band (band allocated for Industrial, Scientific, Medical purposes). Lower frequencies cannot be selected, because the antenna length is inversely proportional to the transmission frequency. Choosing of very high frequencies are also limited since the power consumption and transmission distance covered becomes a factor. So the frequency range around 315 MHz to 915 MHz can be chosen for optimum operation. .
Figue 4: RF transceiver interface to microntroller The modulation format used may be of FSK, ASK, MFSK, OOK, etc. FSK (Frequency Shift Keying) modulation is used because of its noise tolerance capability compared to other techniques. Transceivers with FHSS (Frequency Hopping Spread Spectrum) facility are to be chosen for better immunity to noise The RF transceiver is interfaced to the microcontroller through the Serial Peripheral Interface. The RF transceiver and microcontroller interface is shown in fig.4. In this case microcontroller acts as the master issuing commands and sending
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data which are to be transmitted and RF transceiver functions as the slave.. Data can be transmitted wirelessly via RF transceivers at instants. The transceiver is allowed to enter power down mode while not transmitting and wake on radio feature is to be enabled. Instead of starting from the transceiver chip and integrating all other necessary components, we can directly use the transceiver module available in the market. These modules have antennae, external power amplifier and other necessary resources.
Software Design The microcontroller of the data logger was appropriately programmed to collect the energy information from the data logger and transfer it to the RF transceiver and the memory card. The flowchart of the microcontroller program is shown in fig.5. The initialization of all the devices is done first. Then the microcontroller checks the time. If the time matches the programmed instants, it wakes up the transceiver to transmit data wirelessly. Else, it will check for request from the other end and transmits the data; otherwise it enters into the power down state. The RF transceiver is active only at the time of transmission else it goes into idle mode. The RF transceiver transmits the data at instants wirelessly. On the monitoring station RF transceiver receives the transmitted data and it can be analyzed by programming the personal computer. Microcontroller is programmed in such a way that it transmits data through RF transceiver at instants and also upon request from the monitoring station side.
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Figure 5: Flowchart of microcontroller program
Results The snapshot of the setup established to monitor energy information wirelessly is shown in the Fig 6.. It consists of the load connected to the energy node, data logger, RF transceiver, etc in the energy station side. Data logger displaying energy information snapshot is shown in Fig .7. In the monitoring station RF transceiver to receive data, microcontroller and PC is present. The data logger gets the energy information from the energy node and sends it to the RF transceiver along with the time stamp obtained from RTC for wireless transmission. The received data is displayed in the HyperTerminal of the PC of the monitoring station. The lamp load is used for checking. Energy information collected by the data logger along with time are displayed in the LCD. The result of the energy information displayed in the PC of monitoring station with and without load is shown in Fig 8.(a) and Fig 8.(b) respectively. Energy node ID, Three phase voltage, current, power factor, frequency etc were displayed in the PC.
Implementation of Wireless Data Logger to Monitor Energy in Industries
Figure 6: Snapshot of the Energy Monitoring system prototype
Figure 7: Data logger displaying energy information
Figure 8 (a): Energy information-with lamp load
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Figure 8 (b): Energy information-without load
Conclusion The prototype is a compact and lightweight unit, which can record multiple sessions of data. The development of a miniaturized wireless module suitable for industrial monitoring has been presented. Consequently, the proposed system can be applied to monitor other data. A half-duplex bi-directional communication has been established between the two ends of the wireless link taking advantage of the high data rate of the transceiver The unit is self sufficient in operation and flexible enough to be used with various systems. Thus the energy in industries can be monitored wirelessly.
Acknowledgement The work is supported by Central Scientific Instruments Organization, CSIR Madras Complex, Chennai. The author thank Mr. G.S. Ayyappan, Scientist, CSIO, CSIR Madras Complex for his guidance and support.
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