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An Overview on Voltage Regulators – Construction, Working and Different Applications  

 

A voltage regulator is an electrical device whose sole purpose is to maintain a constant output voltage. It provides the desired output voltage regardless of any change in the input voltage or load conditions. Electronic circuits are dependent on voltage regulators since they require a stable voltage supply to avoid damage.

 

How does it work?

The voltage regulator uses the principle of a feedback control system. It relies upon negative feedback control loops.

 

How Voltage Regulator works diagram

 

As you can see, a reference voltage signal is provided to the comparator circuit along with the feedback signal from the controller. The comparator circuit compares both values and sends the error signal to the controller. The controller regulates the output voltage using the error signal from the comparator.

 

Types of Voltage Regulators

Throughout the world, voltage regulators are the most common electrical component in any machine or device. There are two fundamental types of voltage regulators:

 

Linear Regulator

A linear voltage regulator works like a voltage divider. The resistance of the linear regulator varies with the connected load and input voltage. Therefore, it is able to supply a constant voltage signal.

 

Advantages and Disadvantages

Linear regulators have a lot of advantages, for example, it provides a low ripple voltage that means less fluctuation in the output voltage signal. It has a fast response time. Moreover, it has low electromagnetic interference and less noise.

 

The efficiency of the linear voltage regulator is low and it dissipates a lot of heat so a heat sink is needed. It also requires more space. One of the main disadvantages is that the output voltage cannot exceed the input voltage.

 

Types of Linear Voltage Regulator

  • Shunt
  • Series

 

Shunt Regulator

A shunt regulator is used for low-powered circuits. It works by directing the current away from the load and sending it into the ground. It provides a path from the input voltage to a variable resistor which is connected to the ground. It has a very low efficiency but since the wasted current has a very low value, it is neglected.

 

Applications

  • Used to absorb current (Sink circuits)
  • Amplifiers
  • Voltage power supplies
  • Electronic circuits that need a precise voltage reference

 

Series Regulator

The operation of a series voltage regulator is dependent upon the variable component which is connected with the load. When the resistance of the variable component is changed, the voltage drop across the component also changes. Using this technique, the voltage across the load remains the same.

One of the main advantages is that since the variable component and the load are connected in series, the current flowing through them is the same. Thus, the load effectively uses the current. Which makes it more efficient than a shunt regulator.

 

Switching Voltage Regulators

Switching voltage regulators consist of a series device that is repeatedly switched on and off at a high frequency. The duty cycle is used to control the amount of charge supplied to the load. The duty cycle is controlled by a feedback system that is very similar to the one in the linear regulator. Switching regulators have a high efficiency because the load is either on or off which means it dissipates no energy when it is off.

The switching regulator is superior to the linear regulator when it comes to the output voltage. Because it can supply an output voltage signal which can be greater than the input voltage. Furthermore, it can even generate an opposite polarity voltage signal.

 

Types of Switching Regulators

  • Step Up (Boost)
  • Step Down (Buck)
  • Step Up/Step Down (Boost/Buck)

 

Step Up Regulator

Also known as a boost regulator, Step up regulators generate a higher output voltage signal by increasing the input voltage signal. This type of regulator is most commonly used to power multiple LEDs.

Step Up Voltage Regulator

Step Down Regulator

Step Down regulators are also called buck regulators. They supply a lower regulated output voltage signal from a higher unregulated input voltage signal.

Step Down Voltage Regulator Diagram

Step Up/Step Down Regulator

The purpose of this regulator is to increase, decrease or invert the voltage signal. Moreover, it is also called a voltage inverter circuit. Opposite polarity is achieved by the forward and reverse biasing action of the diode. During the off-time, the circuit charges the capacitor and when the capacitor is fully charged, it supplies the opposite polarity output. The efficiency of this type of voltage regulator is very high.

Stepup-Step down Voltage Regulator

Transistor Voltage Regulator

Zener diodes have a mode due to which it can act as a voltage regulator. This mode is known as the reverse breakdown voltage operation. During this mode, the Zener diode maintains constant output DC voltage signal while the AC ripple voltage signal is completely blocked.

Transient Voltage Regulator

Applications of Voltage Regulators

There are many applications of voltage regulators. One of the most common examples is the mobile charger. The adapter is supplied with an AC signal. However, the output voltage signal is a regulated DC signal.

Every power supply in the world uses a voltage regulator to provide the desired output voltage. Computers, televisions, laptops and all sorts of devices are powered using this concept.

Small electronic circuits rely on regulators to operate. Even the slightest fluctuation in voltage signal can damage the components of a circuit such as ICs.

When it comes to power generation systems, voltage regulators play an essential part in its operation. A solar power plant generates electricity based on the intensity of sunlight. It needs a regulator to ensure a regulated constant output signal.

 

 

 

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Rheostat Overview – Construction and Working, Different Applications

 

Rheostats are resistors which are adjustable, and are used when applications require current adjustment or different resistance in an electrical circuit. Rheostats can adjust generator features, low lights, and start or stable the speed of electrical motors.

There are two things that affect the amount of current flowing into an electric circuit: the magnitude of the applied voltage and the overall resistance of that circuit. If the circuit resistance is lowered, the electric current flow that is passing through the circuit increases. Conversely, the electric current is limited if the circuit resistance is increased.

There is direct relation between the length of the wire to the resistance of the circuit. Increasing the length of the wire increases the resistance between in the circuit. Rheostats allows resistance to be changed, which in turn, either increases or decreases the current through the circuit. The need to add different resistors for varying resistances automatically disappears since a single rheostat can incorporate different resistances necessary for the circuit depending upon its range.

 

Construction and Working

 

A rheostat is a wire wound variable resistor which has two connection points: one is a moving point and the other one is a fixed point. Similar to a potentiometer, some rheostats can have three connection points (A, B, and C) as shown in Figure 1, but still, only two of them are used. In such cases, there are two fixed points (A and C), only one of which is used, and the second connection point is the moving one (B).

Rheostats also have to bear large currents when compared with potentiometers. Therefore, rheostats are made up of wire wound resistors. They are mainly constructed by wrapping the Nichrome wire across a ceramic core. Such a core behaves as an insulator to the heat energy and does not permit it to flow through the rheostat.

 

 

Rheostat Diagram

Figure 1 Rheostat internal Structure (Linear)

 

 

Figure 1 explains the working principles of a rheostat. As mentioned above, rheostats work on the principle that the resistance of a certain track or wire depends upon its length. Let’s assume that we are using the fixed connection point A and the moving connection point B of the rheostat illustrated in Figure 1. The rheostat will offer minimum resistance to the circuit if the slider lies closer to point A, since the resistive coil length is at a minimum. Therefore, a large current can flow through the circuit in this case.

Similarly, the rheostat will offer maximum resistance if the slider lies closer to point C, as the resistive coil length is at its maximum. Hence, a tiny amount of current would flow through the circuit and a large part of the current would be opposed by the rheostat.

Now, let’s say that we are using the fixed connection point C and the moving connection point B. In this case, when the slider is made to lie near point C, the rheostat would offer minimum resistance and maximum current flow through the circuit. Likewise, when the slider is moved near to point A, the rheostat would offer maximum resistance and minimum current flow through the circuit.

Finally, it is important to know the maximum and minimum resistances necessary for your circuit. Rheostats have maximum and minimum resistance ratings, and thus, they cannot offer resistance outside their inherited range.

Now you may be wondering if there is a high point up to which the resistance may be decreased or elevated inside the rheostat. For all rheostats, they come with a resistance rating, for instance if 50kω is the rating of the rheostat, the minimum resistance it will deliver is zero and the maximum will be near 50kω.

 

Different Applications

 

Rheostats are used in situations where high voltage is needed to transmit electricity. They either work as a variable resistor or as a potential divider. An example of rheostats working as a variable resistor is in dimmers. Fan dimmers and light dimmers frequently use rheostats to control the variation of speed and the intensity of light respectively.

Rheostats are used to change the intensity of light when the lights are dim. The flow of electric current decreases through the bulb. If rheostats resistance is increased the light brightness is lessened. Similarly, The flow of electric current increases through the bulb. If rheostats resistance is increased, the light brightness is increased.

When the rheostat amplifies its resistance, the electric current through the bulb is reduced and the light dims. This same process would slow a ceiling or portable wall fan. Radios are equipped with rheostats to manage volume. Motor speeds can also be controlled through rheostats. They can also be used to control temperature in an oven, a heater or an apartment.

Rheostats also work as potential dividers. Wheatstone bridge applies the same potential dividing principle. Different types of resistive sensors use the potential dividing technique, strain gauges, light dependent resistors and thermistors. Rheostats can be used to measure the resistance of a sensor through a microcontroller. Rheostats can accomplish high voltage readings as well as accurate logic level shifting.

Rheostats are still a primary and common component to control the discharging of current in an electrical circuit. However, solid state devices like triacs and silicon-controlled rectifiers (SCR) have taken the place of rheostats. Rheostats are less efficient than a triac and are less reliable because of presence of mechanical components.

They are mostly when circuits need to be tuned or calibrated. High voltage power lines also use rheostats as potential dividers. Low current and high voltage induce minimal losses in power transmission. This helps supply electricity to millions of homes around the globe.

 

 

 

 

Proximity Sensors – Different types, Functionalities, Applications and Market trends

 

There are many different types of sensors available today in the electronics market. Our focus in this discussion is a type of sensor technology called a proximity sensor. We will explain how proximity sensors work, the various types, and what these sensors are used for. We will also cover the increasing relevance of this technology as we move forward into the future. 

 

What are proximity sensors?

Proximity sensors detect how far away a target (object being measured) is without physical contact. 

 

How do proximity sensors work?

Depending on the type of proximity sensor, it will either emit an electromagnetic field, infrared radiation, sound or light beam. Once the beam/field is emitted from the sensor,  it looks for any differences and changes in the return signal and then can determine the distance of the target.

 

What are proximity sensors used for?

They can be found in many different applications including, but not limited to, autonomous cars, smart phones, aircrafts, smart factories, etc. 

 

What are the different types of proximity sensors?

There are many different types including inductive proximity sensors, magnetic proximity sensors, capacitive proximity sensors, photoelectric proximity sensors, and ultrasonic proximity sensors.

 

Inductive Proximity Sensors

This type of sensor is best used for detecting metal. The sensor can detect the distance of any metal object within the magnetic field. 

Inductive proximity sensors are frequently built into metal fixtures. To prevent the sensor from detecting that metal fixture these applications require a shielded inductive proximity sensor. 

Shielded inductive sensors increase the accuracy of the sensor but compromise on range. Unshielded inductive sensors have longer range but can not be mounted on or in certain metals. 

Inductive proximity sensors are commonly used in industrial and military applications. One use case for the military is landmine detection. 

 

Inductive Proximity Sensor

Figure 1 : Inductive Proximity Sensor Diagram 

 

Magnetic Proximity Sensors

This type of sensor can detect a variety of materials including metals, plastics and wood. These sensors includes a reed switch that detects nearby magnets. The reed switch makes contact when it nears a magnet and alerts the sensor. 

These sensors are commonly used in large data/server centers and also in clean energy applications such as wind turbines and solar panels. 

 

Capacitive Proximity Sensors

This type of sensor is able to detect metals and non-metals.  Capacitive proximity sensors use two conduction plates that work like an open capacitor with air in between them. When something enters the sensors field, capacitance occurs and the system is alerted. 

Capacitive proximity sensors are commonly used in industrial applications, specifically in automated production lines where they help in operating machine systems and positioning moving parts. 

 

Capacitive Proximity Sensor

Figure 2: Capacitive Proximity Sensor

 

Photoelectric Proximity Sensors

This sensor works very well in areas where there are a lot of airborne contaminants.  They work by emitting visible/invisible light to a receiver. If the beam of light is blocked, and the receiver detects a disruption or total blockage in the light beam, the system is alerted. Systems can either be alerted when light is received or when it is not received, depending on whether the sensor is a dark-on or light-on sensor. 

These sensors are commonly used for automated doors, detecting colors, materials/ logistic applications, and for counting small objects.

 

Ultrasonic Proximity Sensors

This type of sensor emits sound waves from a transducer at very high frequencies. The sensor waits for the sounds to be reflected back and based on the time period, the sensor can accurately determine the distance of the target. 

This type of sensor is used in self parking technology, anti-collision systems, manufacturing, and obstacle detection. 

 

Proximity Sensor Market

The proximity sensor market in 2019 was valued at $2.94 billion and is projected to reach $4.45 billion by 2025, growing at a rate of 7% year over year. 

Much of this growth is a result of increasing investment in automation hardware. This includes the likes of healthcare, industrial, automotive and smartphone markets. 

Automotive markets are predicted to carry the largest amount of market share. We see a few different applications of proximity sensors in these markets.

For a touch-free user experience auto companies are equipping their vehicles with proximity sensors that allow keyless entry, 3D passenger modeling and interior lighting control. Proximity sensors are also being used in vehicles for parking assistance, anti-collision and fully autonomous driving systems.  

Lastly, we also expect to see a significant increase of proximity sensors in the smartphone market. Many smartphones already have proximity sensors. Their main purpose is to conserve battery life by turning the display screen on or off based on your distance to the phone. For instance, you may notice how your smartphone turns its display off when the phone is placed up to your ear, or turns its display on when you’re looking at the screen. 

In fact, Apple has created technology with proximity sensors that detects when your phone is falling, and prepares itself for an impact. 

Clearly the applications for proximity sensors are seemingly endless. These are just a few examples of how they are being used today. As innovative technologies and products continue to be developed, we can expect exponential market growth. 

 

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Bridge Rectifiers 

 

What is a Rectifier?

In the electronics industry, one of the most popular applications of semiconductor diodes is to convert alternating current (AC) signal of any frequency, which is typically 60 or 50 Hz, to a direct current (DC) signal. This DC signal can be used for powering electronic devices, rather than batteries. The circuit which converts the AC into DC signal commonly consists of a particular arrangement of interlocked diodes and is known as a rectifier. In power supply circuits, two types of rectifier circuits are commonly used — half-wave and full-wave. Half-wave rectifiers only permit one-half of the cycle through, whereas full-wave rectifiers permit both the top half and bottom half of the cycle through, while converting the bottom half to the same polarity as the top. This difference between them is shown in Figure 1.

Difference between outputs of half- and full- wave rectifiers

Figure 1 : Difference between outputs of half- and full- wave rectifiers

 

Between the two types, the full-wave rectifier is more efficient as it uses the full cycle of the incoming waveform. There are two types of full-wave rectifiers — the center-tapped full-wave rectifier, which requires a center-tapped transformer, and the bridge rectifier, which does not need a center-tapped transformer.  The bridge rectifier will be discussed in this article as it is the most popular and usually comes in preassembled modules, making them easier to use.

 

How does a Bridge Rectifier work?

Bridge Rectifiers use four diodes that are arranged cleverly to convert the AC supply voltage to a DC supply voltage. The output signal of such a circuit is always of the same polarity regardless of the polarities of the input AC signal. Figure 2 depicts the circuit of a bridge rectifier with diodes interlocked in a bridge configuration. The AC signal is applied at the input terminals a and b, and the output is observed across the load resistor R1.

Figure 2 Bridge Rectifier with load resistor

Figure 2 Bridge Rectifier with load resistor

 

Let’s see how this rectifier circuit responds to an AC signal with changing polarities at every cycle:

  1. In the first positive half cycle of the AC signal, the diodes D2 and D3 become forward biased and start conducting. At the same time, the diodes D1 and D4 will be reverse biased and will not conduct. The current will flow through the load resistor via the two forward-biased diodes. The voltage seen at the output will be positive at terminal d and negative at terminal c.
  2. Now, during the negative half cycle of the AC signal, the diodes D1 and D4 will be forward biased and diodes D2 and D3 will become reverse biased. The positive voltage will appear on the anode of D4, and negative voltage will be applied to the cathode of D1. It is worth noting at this point that the current that will be flowing through the load resistor will have the same direction as it has with the positive half cycle. Therefore, no matter the polarity of the input signal, the output polarity will always be the same. We can also say that the negative half cycle of the AC signal has been inverted and is appearing as a positive voltage at the output.

 

How does the capacitor work as a filter?

Nonetheless, this output voltage of single polarity is not pure DC voltage, as it is pulsating and not a straight line in nature. This problem is quickly solved by connecting a capacitor in parallel with the load resistor as shown in Figure 3. In this new design, the positive half cycle will charge the capacitor via the diodes D2 and D3. And, during the negative half cycle, the capacitor will stop charging and will begin to discharge itself through the load resistor.

 

Bridge Rectifier with load resistor and filter capacitor

Figure 3 Bridge Rectifier with load resistor and filter capacitor

 

This process is known as filtration, and the capacitor acts as a filter. The capacitor has improved the pulsating nature of the output voltage, and it will now only have ripples. This waveform shape is now much closer to a pure DC voltage waveform. The waveform can be further improved by using other types of filters such as an L-C filter and pie filter.

 

Types of Bridge Rectifiers

The bridge rectifier just discussed is a single-phase type, however, it can also be extended to a three-phase rectifier. These two types can be further classified into full controlled, half controlled, or uncontrolled bridge rectifiers. The circuit that we just discussed is uncontrolled since we cannot control the biasing of the diode, but if all the four diodes are replaced with a thyristor, its biasing can be controlled by controlling its firing angle via its gate signal. It results in a fully controlled bridge rectifier. In a half controlled bridge rectifier, half of the circuit contains diodes, and the other half has thyristors.

 

 

Applications of a Bridge Rectifier

  • For supplying polarized and steady DC voltage in welding.
  • Inside power supplies
  • Inside battery chargers
  • Inside wind turbines
  • To detect the amplitude of modulating signals
  • For conversion of high AC to low DC voltage

 

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