211 SRI RAMAKRISHNA MISSION VIDYALYA POLYTECHNIC COLLEGE.

  Applications of Brushless DC Motors (BLDC) Brushless DC Motors (BLDC)   are used  for a wide variety of application requirements such as varying loads, constant loads and positioning applications in the fields of industrial control, automotive, aviation, automation systems, health care equipments, etc. Some specific applications of BLDC motors are Computer hard drives and DVD/CD players Electric vehicles, hybrid vehicles, and electric bicycles Industrial robots, CNC machine tools, and simple belt driven systems Washing machines, compressors and dryers Fans, pumps and blowers

 Optocouplers manage to send signals between circuits with separate grounds, providing an isolated galvanic barrier between them. Therefore, an optocoupler is a solution for circuits that need to be isolated from each other for safety or regularity reasons and need to have interaction in between. In brief, Optocoupler’s galvanic isolation provides these benefits:   Prevent ground loops in equipment that drives a remote load . Most ac-operated switching supplies (e.g., those used in computers, telecommunications, and instrumentation) use optocouplers for the isolated feedback path.   Suppress electrical noise effects.  For example, it is difficult to take full advantage of a 16-bit ADC because the digital output signals (and noise on the digital ground to which you connect the converter’s output) get back into the analog front end. You can extricate yourself from noise with optical isolation of the digital half.   To get a signal up to a circuit floating at high voltage.  Designers of h

 Permanent Magnet Moving Coil Instrument PMMC, Overview: PMMC means permanent magnet moving coil. It is analogue instrument which is used for measuring the current. It is also known as D’Arsonval meter. In this instrument there are two things one is permanent magnet which is an object or material that generates a magnetic field and other is moving coil through which current will flow. Permanent magnet will be used to generate magnetic field the magnetic field generated by this permanent magnet will not visible to the naked eye. It is solely responsible for the unique property of a magnet that attracts ferromagnetic metals such as iron, cobalt and nickel. It either attracts or repels other magnets. A permanent magnet moving coil (PMMC) instrument cannot measure ac current. It can measure only direct current (DC). We can make ammeter and voltmeter from PMCC. The current that we need to measure is passes through the moving coil as we know that this coil is placed in two permanent magnets

 Hydrometer or Lactometer A   hydrometer   or   lactometer   is an instrument used for measuring density or   relative density   of   liquids   based on the concept of   buoyancy . They are typically   calibrated   and   graduated   with one or more scales such as   specific gravity . Schematic drawing of a hydrometer. The lower the density of the fluid, the deeper the weighted float  B  sinks. The depth is read off the scale  A . A hydrometer usually consists of a sealed hollow glass tube with a wider bottom portion for  buoyancy , a  ballast  such as  lead  or  mercury  for stability, and a narrow stem with graduations for measuring. The liquid to test is poured into a tall container, often a  graduated cylinder , and the hydrometer is gently lowered into the liquid until it floats freely. The point at which the surface of the liquid touches the stem of the hydrometer correlates to relative density. Hydrometers can contain any number of scales along the stem corresponding to properti

Auto Transformer Construction A transformer basically consists of two parts Conductors Core The conductors in the autotransformer are made up of copper.  They are of low resistance. The copper conductors are insulated with each other . The material used for insulation is impregnated paper, mica, etc.  The insulation also helps in reducing eddy current losses.  The winding is wound around the core. For a single winding transformer, the requirement of copper is less as compared to two winding transformers. auto-transformer-construction To transfer flux from primary to the secondary, core is used.  The core is made up of magnetic material like silicon steel, CRGO steel, etc.  CRGO steel is the most efficient material for core, as it has the least hysteresis losses. The role core is to transfer flux from one part of winding to other parts.

  Applications of Induction Generators: Existing Supply or Grid conected induction generators used for Small and variable amounts of Water power generated hydraulic turbines, Load driving hoists for generating braking torque. Self-excited induction generators are used for power generation using renewable energy sources like windmill generators, in isolated places. Induction generators are also used as stand-alone power supply units for loads in remote places. Doubly fed induction generators used in wind power plants. The advantage of DFIGs is to maintain a reliable operation of the network with improved power quality.

 Static characteristics of Sensor: It is about how the output of a sensor changes in response to an input change after steady state condition. Accuracy: Accuracy is the capability of measuring instruments to give a result close to the true value of the measured quantity. It measures errors. It is measured by absolute and relative errors. Express the correctness of the output compared to a higher prior system. Absolute error = Measured value – True value Relative error = Measured value/True value Range: Gives the highest and the lowest value of the physical quantity within which the sensor can actually sense. Beyond these values, there is no sense or no kind of response. e.g. RTD for measurement of temperature has a range of -200`c to 800`c. Resolution: Resolution is an important specification for selection of sensors. The higher the resolution, better the precision. When the accretion is zero to, it is called the threshold. Provide the smallest changes in the input that a sensor is abl

  Applications of Astable Multivibrator 1.  The Astable Multivibrator circuit mainly used as a continuous wave generation circuit. 2.  Astable Multivibrators are used in  Frequency Modulation  Circuits. 3.  Astable Multivibrators are used in analog as well as digital timer Circuits. 4.  They are also used in Voltage to Frequency converter circuits. 5.  Astable Multivibrator circuit can generate also Square Wave, for this reason, they are used in digital transmission, receiver, television broadcast, etc. 6.  They are used for pulse synchronization or pulse position modulation. 7.  They are used as timing oscillator or clock in a  computer  system. 8.  They are used in Radio Equipment such as Transmitter and Receiver Circuit. 9.  In earlier days, astable multivibrators are used for morse code generation. 10.  They are used in digital  Flip-Flop Circuits ,  Electronic Register  Circuits. 11.  They are used in flashing lights, automatic switching circuits. 12.  They are used for speed cont

  What is a computed tomography (CT) scan? The term “ computed tomography ,” or CT, refers to a computerized x-ray imaging procedure in which a narrow beam of  x-rays  is aimed at a patient and quickly rotated around the body, producing signals that are processed by the machine’s computer to generate cross-sectional images, or “slices.” These slices are called tomographic images and can give a clinician more detailed information than conventional x-rays. Once a number of successive slices are collected by the machine’s computer, they can be digitally “stacked” together to form a three-dimensional (3D) image of the patient that allows for easier identification of basic structures as well as possible tumors or abnormalities. Unlike a conventional x-ray—which uses a fixed x-ray tube—a CT scanner uses a motorized x-ray source that rotates around the circular opening of a donut-shaped structure called a gantry. During a CT scan, the patient lies on a bed that slowly moves through the gantry

  Power Line Communications (PLC) allows transmission of data over power lines. PLC is potentially the network with the deepest capillarity in the world, since power lines are almost ubiquitous. Powerine communications is a rapidly evolving market that utilizes electricity power lines for the high-speed transmission of data and voice services.           PLC works by transmitting high frequency data signals through the same power cable network used for carrying electricity power to household users. Such signal cannot pass through a transformer. This requires devices ("outdoor devices") that combine the voice and data signals with the low-voltage supply current in the local transformer stations to bridge the last mile. In the house, "indoor devices" (adapters) are used in order to filter out the voice and data signals and to feed them to the various applications (e.g. PC/Internet, telephone, etc.).           The technology has roots going back to the 1940s. It has bee

  In   electronics , a   ferrite core   is a type of   magnetic core   made of   ferrite   on which the windings of electric   transformers   and other wound components such as   inductors   are formed. It is used for its properties of high   magnetic permeability   coupled with low   electrical conductivity   (which helps prevent   eddy currents ). Moreover, because of their comparatively low losses at high frequencies, they are extensively used in the cores of   RF   transformers and   inductors   in applications such as   switched-mode power supplies , and ferrite   loopstick antennas   for AM   radio receivers . Several ferrite cores Ferrites Edit Ferrites are ceramic compounds of the  transition metals  with  oxygen , which are  ferrimagnetic  but non-conductive. Ferrites that are used in  transformer  or  electromagnetic   cores  contain  iron  oxides combined with  nickel ,  zinc , and/or  manganese  compounds. They have a low  coercivity  and are called" "soft ferrite