There are different types of projects based on the temperature indicator. Now, here we are explaining about the temperature indicator with the LED display by using a temperature sensor. This project shows the use of a V/F converter monitoring temperature in degree Fahrenheit (F). The benefits of the LED temperature indicator are it can calculate the room temperature, atmospheric temperature, and body temperature. This article discusses the block diagram & circuit diagram of the LED temperature indicator.
Block Diagram of LED Temperature Indicator
The following diagram shows the block diagram of LED temperature indicator. The block diagram consists of a temperature sensor, amplifier, V/F converter, three digital BCD converters, time base, and LED display. This project is based on the V/F converter in monitoring temperature in degrees Fahrenheit.
Circuit Diagram of LED Temperature Indicator
The circuit shows the schematic diagram of LED temperature and it is planned to display the temperature from 00 to 1000F. The operation of the LED temperature indicator is following. The temperature sensor output changes linearly as a function of temperature. The input of the summing amplifier is the out of the temperature sensor, for the desired temperature & intended range it is used for calibrating the output of the temperature sensor. The R4 potentiometer is attuned thus, the suitable voltage is present at the output of the summing amplifier.
The output of the temperature sensor is directly proportional to the temperature changes. The potentiometer R4 is adjusted at a single temperature. The summing amplifier output drives the inverting amplifier. There are two reasons for the inverting amplifiers first one is, to invert the input thus its output is a positive voltage and it is required for the V/F converter. The other one is to get a suitable gain, it depends on the voltage to frequency scaling and it is applied to the V/F converter.
The input of the V/F converter is from the output of the inverting amplifier. Thus the output of the frequency is directly proportional to the voltage output of inverting amplifier. Let us consider an example i.e., when the temperature increases, then the voltage output of the summing amplifier increases in the negative direction. But the inverting amplifier increases in the positive direction, it causes the frequency of the V/F to increase in the positive direction.
To generate the clock signals from the three digit BCD counter, the output frequency of the converter is AND gating signal. The BCD output of the counter drives the three LED displays sequentially via the BCD-to-seven segment decoder/latch/driver stage, and the temperature is displayed on the LEDs, depending on the relationship between the frequency of the V/F converter and the gate signal. With the help of the time base circuit the gate, latch, and reset signals are generated, it consists of two one-shot multivibrator and free running multivibrator.
LM334 Temperature Sensor
The following pin diagram shows the temperature sensor of LM334, it consists of three terminals which are +V, -V and R. It is a three terminal adjustable current source and its current can be programmed from 1µ to 10mA and it contains one external resistor R1. This temperature sensor has a wide range of operating voltage from 1 to 40V and it can also perform the reverse voltage up to 20V when the positive voltage terminal is negative with respect to the negative voltage terminal.
The LM334 temperature sensor is designed to operate the temperature range of 0 to 700 C. AD590 temperature sensor is used for a wider range of temperature from 550 to 1500 C. The output of the LM334 temperature sensor changes up to 10 MV/K, we can consider that 00F is equal to 2552.2 mg and it should be scaled down to 0V. Thus the temperature will be displayed in the Fahrenheit degrees and it can be able by summing amplifiers, in particular, the potentiometer R4 of the summing amplifier is adjusted, therefore the output is 0v.
Thus the same process is repeated for calibrating the output of the summing amplifier for other values of 0F. The following table shows the relationship between different temperature units like K, C, F, with their output of the temperature sensor. The summing amplifier is of the corresponding value of temperature because the output of the sensor is directly proportional to the temperature.
|Kelvin K||Degree Celsius||Degree Fahrenheit||Output of the temperature sensor (mV)||Output of the summing amplifier (mV)|
Applications of LED temperature Indicator
The following are the applications of the LED temperature indicator
- LM334 is an accurate sensor and it will give the output without an error
- In this, the temperature is calculated directly in degree centigrade
- It is a 10mV/d raises the temperature
The advantages of the LED temperature indicator are following.
- Body temperature
- Atmospheric temperature
- The room temperature can be calculated.
In this article, we will discuss the Electronic Project on LED Temperature Indicator. I hope by reading this article you have gained some basic information about the LED temperature indicator. If you have any queries about this article about the Electronics and electrical projects for engineering students, please feel free to comment in the below section. Here is the question for you, what are the functions of the LED temperature indicator.