## Synchro Position Transducer Working Principle

We know that Syncro is an inductive device which works on the principle of rotating transformer. Here the term rotating transformer means the primary to secondary coupling can be changed by physically changing the relative orientation of the winding. So based on this working principle of syncro we can use it as position transducer.

### Construction of Position Transducer:

Position transducer is one of the basic application of the Synchro. It uses dumb-bell shaped rotor. Single phase ac supply is given to the rotor of the Synchro. This rotor is mechanically coupled with the shaft of rotating element whose angular position is to be determined.

### Position Transducer Working Principle:

We know that the stator of the synchro has three windings. These three winding of the stator are connected in star connection. Remaining ends of each winding are taken out to connect them with the voltmeter as shown in the figure. When the angle of the rotor changes the output voltage i.e. the stator voltages of each winding is given by,

E1 = Eom cosθ sin wt = instantaneous voltage for stator windings S1.

E1 = Eom cos(θ+120) sin wt = instantaneous voltage for stator windings S2.

E1 = Eom cos(θ+240) sin wt = instantaneous voltage for stator windings S3.

Where

• θ= angular position of the rotor
• Eom = peak value of voltage of each winding
• w= 2πf
• f= frequency of the rotor
• t = time in seconds.

All instantaneous voltages are sinusoidal in nature. But they give different values of voltages at different position of rotor.

Thus using these three values of stator voltages we can easily measure the position of the rotor. Hence Synchro can be used as a position transducer.

### Applications of Position Transducer:

1) For measuring the angle of the rotating machine like antenna platform.
2) Position transducer can be used as ratary position sensor for aircraft control surfaces

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## Audio amplifier using op-amp:

This article provides an information about how to make an audio amplifier using opamp. We will also try to explain the working of this audio amplifier using opamp.

We have already studied some important applications of operational amplifier such as op-amp comparator, op-amp integrator in the previous articles. Today we are going to learn another important application of op-amp as audio amplifier and its working.

We know that the output of most of the communication receivers is the audio amplifier. Important characteristics of ideal audio amplifier are listed below.

1)      High gain.

2)      Distortion should be minimum in the audio frequency range. (20Hz to 20KHz)

3)      Input resistance or impedance should be very high.

4)      Low output resistance to provide optimum coupling to the speaker.

If we use operational amplifier in the audio amplifier, then it will cover all the characteristics listed above so as to make an ideal audio amplifier.

### Circuit diagram:

Following figure shows the circuit diagram of the audio amplifier using operation amplifier.

### Working of audio amplifier:

It should be noted that the op-amp is supplied only from +V volt power supply (usually 5V power supply), the –V terminal is grounded. This arrangement is made so as to get the output in the range (+V-1) volt and +1 volt. In audio amplifier coupling capacitor (Cc2) is used between the op-amp and speaker. Coupling capacitor is necessary to reference the speaker signal around ground. The capacitor Cs is included in the Vcc line to prevent any transient current caused by the operation of op-amp from being coupled back to Q1 through the power supply.

Op amp (IC 741) pin configuration:

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Search topics: op amp as an audio amplifier circuit, audio amplifier circuit using op amp,audio amplifier project using opamp.

## Four point starter:

In four point starters, the hold on coil is connected directly across the supply line through a protective resistance R. when the armature touches stud no 1.the line current divides into three parts i) armature starting resistance and overload release. ii) a variable resistance and shunt field winding. Iii) Holding coil and current limiting resistance.

The basic difference between three point and four point starters is the manner in which the hold on coil is connected. The unnecessary tripping of starter can be stopped by connecting separately or parallel both magnetizing and field coil. They are connected in such a way that both should carry their individual current. Thus voltage drop in one coil will not affect the voltage in other coil.

The only limitation of the four point starter is that it does not provide high speed protection to the motor. If under running condition field gets opened; the field current reduces to zero. As there is some residual flux present and speed (N) is directly proportional to flux (ø) the motor will tries to run with dangerously high speed .this is called high speed action of motor. In three point starter as no volt coil is directly connected to across the supply; its current is maintained irrespective of the current through the field winding .hence it always maintain the handle in run position as long as supply is there .and thus it doesn’t protect the motor from field failure conditions which returns into high speeding of the motor.

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Three Point Starter

## Three point starter:

### Construction:

figure shows the schematic diagram of a three point starter for a shunt motor. It is so called because it has three terminals L, F and A. the starter consist of starting resistance divided into several sections and connected in series with the armature. The tapping points of the starting resistance are brought out to a number of studs. The three terminal L, F and A of the starter are connected respectively to the positive line terminal, shunt field terminal and armature terminal. The other terminal of the armature and shunt field windings are connected to the negative terminal of the supply   .the no volt coil is connected in the shunt field circuit. One end of the handle is connected to the terminal L through the over load release coil. The other end of the handle moves against a spiral spring and make contact with each stud during starting operation cutting out more and more starting resistance as it passes over each stud in clockwise direction.

### Working of three point starter:

1)      Initially when a DC supply is switched ON with handle in the OFF position.

2)     The handle is now moved clockwise to the first stud, the shunt field winding is directly connected across the supply while the whole starting resistance is inserted in series with the armature circuit.

3)     As the handle is gradually moved over to the final stud, the starting resistance is cut out of the armature circuit in steps. The handle is now held magnetically by the no volt release coil which is energized by shunt field current.

4)     If the supply voltage is suddenly interrupted or if the field excitation is accidently cut, the no volt release coil is demagnetized and the handle goes back to the OFF position under the pull of the spring. If no volt coil were not used, then in case of failure of supply. The handle would remain on the final stud. If then supply is restored, the motor will be directly connected across the supply, resulting in an excessive armature current.

5)     If the motor is overloaded (or any fault occurs) it will draw excessive current from the supply. This current will increase the ampere turns of the overload release coil and pull the armature, thus short circuited the no volt release coil. The no volt coil is demagnetized and the handle is pulled to the OFF position by the spring .thus the motor is automatically disconnected from the supply

### Limitations of the three point starter:

Unnecessary tripping of starter if a field regulator is connected in series with the field windings for speed control operation. This combination and magnetizing coil will carry same current if more and more resistance is added in field regulator then current in magnetizing coil is unable to hold the arm in attracted position and unnecessarily the arm will be released even if there is no over loading .this is avoided in four point starter.

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four point starter

## Hall Effect Multiplier – Construction, Working and Applications

Hi friends, in this article we are going to learn Hall Effect Multiplier which can be used in applications where power is to be controlled. Hall Effect Multiplier is also used where the multiplication of signals over a wide range of amplitudes is performed. Now let us see the construction and working of Hall Effect Multiplier.

### Hall Effect:

“When a current carrying conductor is placed in a magnetic field, a transverse effect is noted. This effect is called Hall Effect.” It was discovered by scientist Hall in 1879. Hall found that:

“When a magnetic field is applied at right angles to the direction of electric currents, an electric field is setup which is perpendicular to both the direction of electric current and the applied magnetic field.”

In other words:

“When any specimen carrying a current ‘I’ is placed in the transverse magnetic field B, then an electric field ‘E’ is induced in the specimen in the direction perpendicular to both ‘I’ and ‘B’. The phenomenon is known as Hall effect.”

### Applications of Hall Effect Multiplier:

1. Determining whether a semiconductor is N-type or P-type.
2. Determining the carrier concentration.
3. Calculating the mobility, having measured the conductivity.
4. Magnetic field meter: the hall voltage vH for a given current is proportional to B. hence measurement of vH measure the magnetic field B.
5. Hall Effect multiplier: the instrument gives an output proportional to the product of two signals. Thus if current I made proportional to one input and if B is proportional to second input, then Hall voltage vH is proportional to the product of two signals.

### Hall Effect multiplier:

In applications where the power is to be controlled or processed further Hall Effect Multipliers are used . A Hall Effect multiplier is shown in figure. The Hall Effect multiplier uses a Hall Effect element.

The current is passed through the current coil which produces a magnetic field proportional to the current I .this field is perpendicular to the Hall Effect element. A current Ip, proportional to the voltage, is passed through the Hall Effect element in a direction perpendicular to field as shown. The current is limited by the multiplier resistance Rs. The output voltage of the Hall Effect multiplier is:

vH=KH.Ip.B/t

Where KH =Hall co-efficient  m/A-Wb m^(-2),

B=flux density;Wb/m^2 and t= thickness of hall element ; m.

Now B is directly proportional to Vi

Therefore the output voltage of the Hall Effect multiplier is proportional to instantaneous power.

Hence the voltmeter connected at the output terminals can be calibrated in terms of power. The Hall Effect voltage which is of the power can be processed further for control and other purposes. This is the major advantage of Hall Effect multiplier over electrodynamometer wattmeters the output of the later being the deflection of a pointer which cannot be processed further.

I hope you understood the construction and working of Hall Effect Multiplier and its Applications. If you have any doubts please let us know. Share your doubts in the comments below. If you liked this article please share and like our facebook page.

## Applications of Flip-Flops:

Some of the common uses of the Flip-Flops are as follows:

1)   Bounce elimination switch

2)   Latch

3)   Registers

4)   Counters

5)   Memory, etc.

Some examples of uses of Flip-Flops are given below:

### A)  Bounce elimination switch :

Mechanical switches are employed in digital system as a input devices by witch digital information (0 and 1) is entered into the system. There is a very serious problem associated with these switches which is switch bouncing (chattering).

If we entered input as ‘1’ in a sequential circuit the output is ‘1’ but it oscillates between ‘1’and ‘0’ before come to rest i.e. 1. This changes the output of the sequential circuit and creates difficulties. This problem is eliminated by the use of Bounce elimination switches.

### B)  Registers :

A register is composed of a group of flip-flops to store a group of bits (word). For storing N bit of words we require N number of flip-flops (one flip of for each bit).

A flip flop can store only one bit of data, a 0 or a 1; it is referred to as a single bit register. When more bits of data are to be stored, a number of flip flops are used. A register is a set of flip flops used to store a binary data. The storage capacity of a register is a number of bits of digital data that it can retain. Loading a register means setting or resetting the individual flip flops, i.e. inputting data into the register so that their states correspond to the bits of data to be stored. Loading may be serial or parallel in serial loading, data is transferred into the register in serial form, i.e. one bit at a time, whereas in parallel loading, the data is transferred into the register in parallel form meaning that all the flip flops are triggered into their new states at the same time. Parallel input requires that the SET and/or RESET controls of every flip flop be accessible.

### C)  Counters :

Digital counters are used for count the events. Electrical pulses corresponding to the event are produced using transducers & these pulses counted using a counter.

A digital counter is a set of flip-flops whose stated change in response to pulses applied at the input to the counter. The flip flops are interconnected such that their combined state at any time is the binary equivalent of the total number of pulses that have occurred up to that point. Thus, as its name implies, a counter is used to count the pulses. A counter can also be used as a frequency divider to obtain waveforms with frequencies that are specific fractions of the clock frequency. They are also used to perform the timing function as in digital watches, to create time delays, to crate non-sequential binary counts, to generate pulse trains, and to act as frequency counters, etc.

### D)  Random access memory:

In computers, digital control systems, information processing systems it is necessary to store digital data and retrieve the data as desired.

Flip-Flops can be used for making memories in which data can be stored for any desired length of time and then readout whenever required.

The data stored in RWMs (Read Write memories) constructed from semiconductor devices will be lost if power is removed. Such memory is said to be volatile. But ROM is non-volatile. Random access memory (RAM) is the memory whose memory locations can be accessed directly and immediately. By contrast, to access a memory location on a magnetic tape, it is necessary to wind or unwind the tape and go through a series of addresses before reaching the address desired. Therefore, the tape is called the sequential access memory.