The term SPWM stands for “Sinusoidal pulse width modulation” is a technique of pulse width modulation used in inverters. An inverter generates an output of AC voltage from an input of DC with the help of switching circuits to reproduce a sine wave by generating one or more square pulses of voltage per half cycle. If the size of the pulses is adjusted, the output is said to be pulse width modulated. With this modulation, some pulses are produced per half cycle. The pulses close to the ends of the half cycle are constantly narrower than the pulses close to the center of the half cycle such that the pulse widths are comparative to the equivalent amplitude of a sine wave at that part of the cycle. To change the efficient output voltage, the widths of all pulses are amplified or reduced while keeping the sinusoidal proportionality. With PWM (pulse width modulation), only the on-time of the pulses are changed during the amplitudes.
The most frequently measured environmental quantity is “Temperature” This might be expected since most of the systems are affected by temperature like physical, chemical, electronic, mechanical, and biological systems. Certain chemical effects, biological processes, and even electronic circuits execute best in limited temperature ranges. Temperature is one of the most frequently calculated variables and sensing can be made either through straight contact with the heating basis or remotely, without straight contact with the basis using radiated energy in its place. There is an ample variety of temperature sensor on the market today, including Thermocouples, Resistance Temperature Detectors (RTDs), Thermistors, Infrared, and Semiconductor Sensors.
What is a Temperature Sensor?
Usually, a temperature sensor is a thermocouple or a resistance temperature detector (RTD) that gathers the temperature from a specific source and alters the collected information into understandable type for an apparatus or an observer. Temperature sensors are used in several applications namely HV system and AC system environmental controls, medical devices, food processing units, chemical handling, controlling systems, automotive under the hood monitoring and etc.
The most frequent type of temperature sensor is a thermometer, used to determine the temperature of solids, liquids, and gases. It is also mostly used for non-scientific purposes as it is not so accurate. The different kinds of sensors are categorized by the sensing capacity of the sensor as well as the range of applications. The different types of temperature sensors include the following.
- Resistor temperature detectors
- Infrared sensors
LM35 Temperature Sensor
The LM35 is one kind of commonly used temperature sensor that can be used to measure temperature with an electrical o/p comparative to the temperature (in °C). It can measure temperature more correctly compare with a thermistor. This sensor generates a high output voltage than thermocouples and may not need that the output voltage is amplified. The LM35 has an output voltage that is proportional to the Celsius temperature. The scale factor is .01V/°C.
The LM35 does not need any exterior calibration and maintains an exactness of +/-0.4°C at room temperature and +/-0.8°C over a range of 0°C to +100°C.One more significant characteristic of this sensor is that it draws just 60 microamps from its supply and acquires a low self-heating capacity. The LM35 temperature sensor available in many different packages like T0-46 metal can transistor-like package, TO-92 plastic transistor-like package, 8-lead surface mount SO-8 small outline package.
|1||Vcc||Input voltage is +5V for typical applications|
|2||Analog Out||There will be the increase in 10mV for raise of every 1°C. Can range from -1V(-55°C) to 6V(150°C)|
|3||Ground||Connected to ground terminal of the circuit|
LM35 Temperature Sensor Circuit Diagram
The LM35 temperature sensor is used to detect precise centigrade temperature. The output of this sensor changes describes the linearity. The o/p voltage of this IC sensor is linearly comparative to the Celsius temperature. The operating voltage range of this LM35 ranges from-55˚ to +150˚C and it has low-self heating. This is operated under 4 to 30 volts. The most extensively used electronic devices are operational amplifiers, which are certain kind of differential amplifiers. Temperature sensor circuit has terminals such as two inputs like non-inverting (+) and inverting (-) and only one output pin. Operational amplifier IC741 is used as a non-inverting amplifier. The variation between the i/p terminals amplifies the circuit.
The amount produced by IC2 amplifies in an amount to the temperature by 10 mV per degree. This unstable voltage is supply to a comparator IC 741. OP Amplifier is the most generally used electronic devices today. The IC 741 op-amp is one sort of differential amplifier. We have used IC741 as a non-inverting amplifier which means pin-3 is the input and the output is not inverted. This LM35 temperature sensor circuit amplifies the difference between its input terminals. The advantages of temperature sensor include It has no effect on the medium, more accurate, It has an easily conditioned output and It responds instantly.
Applications of LM35 Temperature Sensor
The applications of LM35 temperature sensor include the following
- Measuring temperature of a particular environment and HVAC applications
- Providing thermal shutdown for a component/ circuit
- Checking Battery Temperature
This is all about temperature sensor circuit and its working principle. We believe that the information given in this article is helpful for you for a better understanding of this project. Furthermore, for any queries regarding this article or any help in implementing the electronics projects, you can feel free to approach us by connecting in the comment section below. Here is a question for you: what do you mean by a heat sensor?
The Servo Motor is a commonly used motor for high technology devices in various industries like automation. This motor is a self-controlled electrical device, that switch part of a machine with high productivity and great accuracy. The o/p shaft of this motor can be stimulated to a specific angle. These motors are mainly used in different applications like home electronics, cars, toys, airplanes, etc. This article discusses what is a servo motor, working, types and its applications.
With the growth in the field of robotics, human involvement has become very less and also automatons are being widely used for security purpose. Day by day, fire accidents have become very common. Sometimes, it may lead to the danger that makes it hard for the firemen to save human life. In these cases, a robot is designed to guard human lives, wealth, and environments from the fire accidents namely fire fighting robotic vehicle. This robot project is an advanced and very useful project for engineering students, who are fascinated to robotics. This project uses RF technology for remote operation & also 8051 microcontrollers. This robot is capable of noticing a fire if a house catches fire when they not present in the house, while somebody in the house is either sleeping. By means of this robot, people and belongings can be protected from fire accidents.
In the year 1971, the theory of memristic was developed by Professor “Leon Chua”. The behavior of the memristor was discovered by an ‘HP Lab Scientist’ while he was trying to find out cross bar switches. Memristor is a switch used to connect several inputs to several outputs in a matrix – that’s why it is also known as matrix switch. Professor Leon Chua had looked at the examples of resistor, capacitor & inductor – from which, he saw a missing component and named it as a memory resistor or memristor. The practical model of the memristor was advanced by Stanley in the year 2006. The memristor technology was developed several decades ago, but it got invented recently.
The term “Temperature” is a physical parameter and it can be measured in units of degrees. It is a critical part of any method to measure precise temperature. The usual applications needful accurate temperature quantities include medical, electrical or electronic studies, biology research, materials research, etc. A Temperature Sensor is used to measure the heat energy amount that let us detect a physical variation in temperature, generating either an analog or digital output.
Types of Basic Physical Temperature Sensors
In general, there are two types of sensing methods are available, namely contact type temperature sensors and non-contact type temperature sensors.
Contact Type Temperature Sensor
The contact type temperature sensor is in physical contact with the substance or object. These sensors are used to measure the temperature of solids, liquids or gases.
Non-contact Type Temperature Sensor
Non-contact type temperature sensors are used to detect temperature by interrupting a part of the emitted IR energy of the substance and detecting its intensity. These sensors can be used to measure only the temperature of solids and liquids. It is not potential to use them on gases due to their transparent nature.
Types of Temperature Sensors
The different types of temperature sensors available in the market can vary from simple ON/OFF thermostatic devices to highly sensitive semiconductor devices. The two basic types of physical temperature sensors like contact and non-contact are further categorized into a voltage, resistive, and electromechanical sensors. The most commonly used temperature sensors are classified into three types such as Thermistors, thermocouples, and resistance temperature detectors.These sensors vary from each other in terms of working parameters. For modest temperature series applications, solid state sensors are also accessible which give the advantage of simple interface and incorporated signal conditioning.
The thermistor is a temperature sensing device that changes the physical resistance with the temperature. Generally, these devices are made from ceramic material semiconductor like cobalt, manganese. It is shaped into small pressed hermetically closed discs that give a comparatively fast response to any temperature variations.
NTC Type Thermistor (Epcos)
Due to the properties of a semiconductor material, these devices have an NTC (negative temperature coefficient), i.e. the resistance falls with the rise in temperature. But, there are also Thermistors available with PTC (positive temperature coefficient), their resistance rises with the rise in temperature.
Application of a Thermistor
The thermistor is rated by their resistance value at room temperature, the time constant, and power rating. The thermistor is a passive resistive device, that requires current to generate an o/p voltage. Generally, they are connected in series with an appropriate biasing resistor to form a potential divider network.
Consider a thermistor with a value of resistance 2.5KΩ at 30°C of and 30Ω at 60°C. Here, the thermistor is connected in series with a 1kΩ resistor across a 5V power supply.
Here, the output voltage of this Thermistor can be calculated as
At 30°C, RNTC = 2500Ω;
Vout=1000/ (2500+1000)*5= 1.42V
At 60°C, RNTC = 30Ω;
Vout=1000/(30+1000)*5 = 4.85V
By substituting the specific resistor value with a potentiometer, we can get an o/p voltage at a prearranged temperature.
Though, it is significant to note that typical resistance values are dissimilar at room temperature for different types of thermistors since they are non-linear. Thermistor has an exponential transform with temperature; so it has a temperature constant (Beta) that is used to analyze its resistance for a given temperature. Though in a voltage divider network, the current which is obtained from the applied voltage is linear with temperature, therefore the o/p voltage across the resistor & temperature are linearly related.
Advantages of Thermistors
The advantages of Thermistors include the following.
- The speed of response is better to changes in accuracy, temperature, and repeatability.
- Compared to RTDs, it is inexpensive
- The range of higher resistance ranges from 2,000 to 10,000 ohms
- Sensitivity is Much higher, i.e., ~200 Ω/°C within a partial temperature range of up to 300 °C
Resistive Temperature Detectors
The term RTD stands for “Resistive Temperature Detector” is an electrical resistance temperature sensor that is made of coils of metals or films like platinum whose electrical resistance is a role of temperature.
Resistive Temperature Detectors have PTC (positive temperature coefficients) and not like Thermistors, they offer precise temperature measurements since they have linear output. But, they have poor sensitivity generating a small o/p change, for instance, 1Ω/°C for a temperature change. Pt100 has been the most frequently available sensor with a typical resistance value of 100Ω at 0°C. The main drawback is its high cost.
How to Use Resistive Temperature Detectors?
Resistive temperature detectors are passive resistor devices such as Thermistors and the flow of current through the sensor to get an o/p voltage is linearly connected to the temperature. But, an error can happen in the reading due to the variation in resistance caused by the self-heating of the flow of current through the resistive wires. To overcome this difficulty, a resistive temperature detector is connected to a resistive bridge n/w with additional connecting wires for lead compensation and/or adding of a constant current source.
Advantages of RTDs
The advantages of resistive temperature detectors include the following.
- The temperature range ranges from -200 to 650°C
- It offers a high o/p for a current drop
- RTDs are more linear compared to Thermistors and thermocouples.
Thermocouples are the most commonly used temperature sensors due to some features like a wide temperature range from below -200°C to over 2000°C, accurate, and are relatively low-cost.
Construction and Working
The construction of a Thermocouple can be done with two different metals that are soldered together producing a slight potential difference (mV) as a function of temperature. One junction is kept at a constant temperature named the reference junction, while the other is the measuring junction. With the temperature difference between the two junctions, a voltage is established across the junction which is used to measure the temperature. The Seebeck effect can be defined as the voltage difference between the two junctions.
If both junctions are at the similar temperature, the potential difference through the junctions is zero, i.e. V1 = V2. However, when the junctions are at dissimilar temperatures connected in a circuit, the o/p voltage is comparable to the temperature difference between the two junctions, i.e. V1 – V2.
Types of Thermocouples
Thermocouples are existing in different materials and temperature ranges; therefore there are different kinds of thermocouples available for precise applications as set by international standards such as E, J, K, N, T, and U. Where, type J &K are the most frequently used thermocouples.
Advantages of Thermocouple
- Temperature ranges are high
- Rough, withstand shock and vibration
- Offers instant response to temperature changes
How to Use a Thermocouple?
Thermocouple gives a few millivolts output voltage for a temperature change of 10°C. So, it is mandatory to increase the output voltage.
It is essential to carefully choose an amplifier to get good drift stability for stopping recalibration of the thermocouple. This makes an Op-Amp (operational amplifier) desirable for most applications.
Thus, this is all about different types of temperature sensors.We hope that you have got a better understanding of this concept.Furthermore, any doubts regarding this concept or to implement any temperature sensor based projects please comment in the comment section below.
The LM324 operational amplifier IC can be worked as a comparator. This IC has 4 independent operational amplifiers on a single chip. This a Low Power Quad Operational Amplifier and it has high stability, bandwidth which was designed to operate from a single power supply over a wide range of voltages. The quad amplifier can operate at supply voltages as low as 3.0 V or as high as 3.2 V with quiescent currents about one fifth of those associated with the MC174.
The TRIAC is the three terminal semiconductor device and used for controlling the current. From the name of the TRIAC, the word Triode is for alternating current and it is effectively developed with the help of the SCR or Thyristor. But the Thyristors are able to conduct the device in one direction and the TRIAC is bidirectional. The Triode For Alternating Currents are able to switch high voltage and high level of current and on both the parts of AC waveforms. This device is used widely in AC power control applications.
The first Arduino board technology was developed by the David Cuartiellers and Massimo Banzi in the year of 2005. This board is a type of Microcontroller based kit and it is designed with low cost & easy to use for the students and professionals to build the device. We can make an Arduino board by using various basic components or it can be purchased from the sellers. Adafruit industries projected in the year 2011 that over 3lakhs Arduino boards had been produced, but in 2013 the year, Arduino boards are 7lakhs in the user’s hand. This technology is used in the operating devices like communication or controlling.
The Bluetooth is a wireless technology, used for transferring the data from one device to the other device. The distance between the two devices is very short from the fixed, mobile device and building personal area network. The Bluetooth technology is developed by the Bluetooth special interest group and its physical range is from 10m to 100m. The Bluetooth device can connect up to seven devices and it is used in the industry like smartphones, personal computers, and gaming consoles, etc. The IEEE standardized Bluetooth as IEEE 802.15.1, but the standards are maintained for short periods.