ENGINEERING ARTICLES

Switching techniques of pulse width modulation (PWM) have been popular in the area of power electronics and drive systems. PWM is commonly used in applications like motor speed control, converters audio amplifiers etc. PWM is used to adjust voltage applied to the motor. There is no single PWM method which can suite for all applications. As per the advanced technology in solid state power electronic devices and microprocessors, various pulse-width modulation (PWM) techniques have been developed for different industrial applications. For the above reasons, the PWM techniques have been the subject of intensive research since 1970s. The main objective of the PWM is to control the inverter output voltage and to reduce the harmonic content in the output voltage. The pulse width modulation (PWM) techniques are mainly used for voltage control. These techniques are most efficient and they control the drives of the switching devices. The different PWM techniques are Single pulse width modulatio...

Bluetooth doorbell is an advance doorbell which shows your image to the person standing at another side of this bell. This doorbell is made already! You can buy a wireless doorbell in any hardware store. However, this one you make yourself! Even better, as you get more confident with Arduino, you can modify it to make it uniquely yours. For instance, what if your Arduino triggers a music player instead of a buzzer to let you know that someone has pressed the button. This is very useful devices for home use. Left side of figure 1 shows the doorbell button, and right side of figure 1 shows the buzzer unit that is tucked away on a shelf inside. Figure 1(a) The doorbell awaits visitors! (b) The buzzer unit sits discreetly on a shelf. Parts Required: In this project, one Arduino waits for a button press, while the other one sets off a buzzer when it detects that the button has been pressed.  2 Arduino Unos 2 XBee wireless modules (Adafruit P/N 128) 2 Adafruit XBee bre...

In this mini-project, you’ll create two identical assemblies, each consisting of an Arduino and XBee, along with a button and a LED. When you press the button on one assembly, the LED on the other one lights up, and vice versa. Figure 1: Control LEDs with XBee-equipped Arduinos. Parts Required: You’ll be making two assemblies, so you need two of everything! Arduinos (x2) XBees (x2) Breakout boards (x2) Pushbuttons (x2) Breadboards (x2) LEDs (x2) Jumpers Project Description: Follow these steps to assemble the XBee test platform:  1. Solder the breakout boards: Solder up your XBee breakout boards if you haven’t already. Depending on your kit, this could mean simply soldering in some header pins.  On other kits, however, you must solder in LEDs, capacitors, and so on.  2. Connect the XBees to the breakout boards: Attach the XBees to their respective breakout boards. This typically involves simply plugging in...

A wound-rotor motor (Slip Ring Motor) is a type of induction motor where the rotor windings are connected through slip rings to external resistances. Adjusting the resistance allows control of the speed/torque characteristic of the motor. Wound-rotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit; as the motor accelerates, the resistance can be decreased. Squirrel Cage Motors have a heavy winding made up of solid bars, usually aluminum or copper, joined by rings at the ends of the rotor. When one considers only the bars and rings as a whole, they are much like an animal's rotating exercise cage, hence the name. PROPERTY SQUIRREL CAGE MOTOR SLIP RING MOTOR Rotor Construction Bars are used in rotor. Squirrel cage motor is very simple, rugged and long lasting. No slip rings and brushes Winding wire is to be used. Wound rotor required attention. Slip ring and brushes are needed also need freq...

Transformers reduce the voltage of the electricity supplied by the utility to a level suitable for use by the electric equipment. Since all of the electricity used by a company passes through a transformer, even a small efficiency improvement will result in significant electricity savings. High-efficiency transformers are now available that can reduce total electricity use by approximately 1 percent. Reduced electricity use provides cost savings for a company. Two types of energy losses occur in transformers: load and no-load losses. Load losses: result from resistance in the copper or aluminum windings. Load losses (also called winding losses) vary with the square of the electrical current (or load) flowing through the windings. At low loads (e.g. under 30 percent loading), core losses account for the majority of losses, but as the load increases, winding losses quickly dominate and account for 50 to 90 percent of transformer losses at full load. Winding losses can be reduce...

1) KNOW THE LOAD CHARACTERISTICS For line-operated motors, loads fall into three general categories: constant torque, torque that changes abruptly, and torque that change gradually over time. Bulk material conveyors, extruders, positive displacement pumps, and compressors without air unloaders run at relatively steady levels of torque. Sizing a motor for these applications is simple once the torque (or horsepower) for the application is known. Load demands by elevators, compactors, punch presses, saws, and batch conveyors change abruptly from low to high in a short time, often in a fraction of a second. The most critical consideration for selecting a motor in these cases is to choose one whose speed-torque curve exceeds the load torque curve. Loads from centrifugal pumps, fans, blowers, compressors with unloaders, and similar equipment tend to be variable over time. In choosing a motor for these conditions, consider the highest continuous load point, which typically occurs a...

MOTOR A motor is an extended version of a transformer. Here we can introduce the analogy between a transformer and a motor that is a motor is like a transformer with a moving secondary. The primary that is not moving is called stator and the secondary that is moving is called rotor. The type of motor that is used worldwide with a greater percentage is the three phase induction motor. The principle is somewhat like a transformer. If we place three coil at 120 degree physical alignment and also apply three phase ac supply which is also with 120 degree electrical phase relation, then the resultant flux, that is created from the vectorial space summation of the three phase fluxes, will rotate at the frequency of the supply voltage. Here the magnitude of the flux is same throughout the rotation. Now this revolving flux will cut the rotor and there will be an induced voltage across the rotor as well. As the rotor is short circuited there will be a flow of current through the short cir...