Temperature monitoring system plays a crucial role in many of the application areas like steel, food, heating systems, medical and other industrial processes wherein a product quality depends on the temperature. This monitoring system uses various temperature sensors like thermistors, RTDs and thermocouples depending on the temperature range. They sense temperature, and the continuous sensing values are directed to the main controller where these values are compared with the predefined limits. Based on the program written in these controllers, actuators are enabled to operate appropriate loads.
The latest monitoring systems also allow a user to change the limits of temperature depending on the requirement of the process. For less-complex applications, simple controllers like microcontrollers are good enough, but for highly-complex processes, the controllers should be PID, programmable logic controllers, or any other advanced controllers.
As the technology is growing, advanced temperature monitoring systems help facilitate the remote monitoring capabilities with the use of wireless technologies like GSM, Bluetooth and Zigbee, and so on. Some of the protocols in industries like CAN, PROFIBUS, Modbus, etc., gather these temperature sensing values to a central room for a supervisory control over the processes.
For a basic understanding of this concept, the following description on simple temperature controllers is based on operational amplifier and microcontroller.
Simple Thermistor Based Temperature Control
This is a simple temperature controller where one preset temperature at a time is possible. The system uses a thermistor as a temperature sensing device, and this device is most frequently used as a temperature sensor because of its low cost. The exceeding temperature limit is indicated by a lamp which is operated by a relay.
We know the concept of op-amp as a comparator; when input at a non-inverting terminal is more than the inverting terminal, then its output is logic high otherwise low. So this circuit is constructed in such a way that, at normal temperature, the comparator output is low because both the inputs are at the same voltage levels.
Negative temperature coefficient thermistor is used as a temperature sensing device, which is connected as one of the input to the operational amplifier. This operational amplifier output activates the relay which further switches the lamp. When temperature exceeds certain limit, then the thermistor’s output at OP-AMP inverting input enables the output to logic high. It then further energizes the relay coil so that the Lamp turns on. This lamp indication tells that the temperature limit is violated. In this way, one can monitor the physical parameters in rooms, offices and industries with the use of simple operational amplifiers.
These are the non-microcontroller based projects that can be further implemented by using ATMEL 8051 microcontroller, and also by using Zigbee as wireless communication for monitoring the temperature in remote areas.
XBEE Based Remote Temperature Monitoring for Transformer
This project is designed to acquire the data of transformers remotely by using a XBEE module. This project uses a temperature sensor, a potential transformer and a current transformer for monitoring the data of the transformer, and sending the data to a remote location. Before discussing about this project, let us know the Zigbee wireless technology that will help you to understand the concept precisely.
Zigbee technology is a wireless communication that makes use of XBEE module as RF. According to an RF communication, the basic RF modules operate at 434MHz frequency. Based on this frequency, the possibility to transmit the data in proper synchronization is nil. XBEE modules operate at a frequency of 2.4 GHz, which is more than the basic RF module’s frequency. By using this XBEE module, data can be transmitted for long distance. Zigbee operates in the industrial, scientific, and medical radio brands as they operate at a frequency of 868 MHZ in Europe, 915 MHZ in the USA and Australia and also operate at 2.4 GHZ worldwide.
Zigbee name discusses mesh networking concept because the message from the transmitter is in zigzag fashion like bees, looking for the best path to the receiver. Zigbee is a compatible product that can be built by any company without paying any license fee for this technology. This is advantageous for Zigbee in the market place.
The analog values of temperature, current and voltage of a transformer are converted into digital values through a DC and these values are then sent to the microcontroller and the data is transmitted to the receiver section through the XBEE module which operates at a frequency of 2.4 Gega Hz.
A power-supply block provides power to this entire transmitter section. The power supply consists of a step-down transformer, which steps downs the voltage to 12V AC voltage, and converts it into a DC by using a bridge rectifier, and it is regulated by a voltage regulator. This regulated DC voltage is used for operating the entire circuit.
The receiver section receives the transmitted data through a XBEE receiver module placed at the receiver section and compares the analog values with the specified limits that are already programmed in the microcontroller.
If temperature, voltage and current values violate the limits, then the microcontroller sends control signals to a relay driver. This relay driver further drives a set of relays that operate different loads. In this system, the loads can be feeders to switch the transformers when a voltage or current exceeds the limits. These parameters are then displayed on the LCD display.
Remote Temperature Monitoring System Applications
Remote temperature monitoring can be used in different areas such as medical refrigerators, blood banks and food storage facilities in which the temperature can be monitored wirelessly which is very essential to control the temperature in different sectors like commercial, industrial, biomedical and government markets.
These systems not only monitor but also provide an alarm for temperature and also monitor the air pressure, airflow and humidity in unique processing applications. Remote temperature monitoring can be done by using a GSM network, and can be applied in server rooms to keep a watch on temperature in inverter rooms, computer rooms and temperature-controlled applications.
This is all about the remote temperature monitoring systems and related projects that can be used in different applications such as medical refrigerators, blood banks and food-storage refrigerators. Thanks for spending your valuable time on this article and for more information about this project, comment in the comments section below.