Monthly Archives: December 2008

AC vs DC – What is the Difference?

AC vs. DC

Electric current is the flow of electrons carrying electric charge. There are 2 types of electric current – direct (DC) and alternating (AC). In Direct Current the electron flow takes place only in one direction. A battery is a source of direct current. DC is widely used in many electronic circuits operating in low voltage levels.

In Alternating Current, both voltage and current alternate in direction back and forth following a sine wave pattern. The number of cycles per second, called the frequency, varies from 50 or 60 depending on the power system in a country. Alternating current is produced universally in power stations using AC generators. The AC theory is briefly described below.

A rotating coil in a magnetic field cuts the magnetic lines of force in two different directions during each half rotation in an AC generator. Thus the current produced travels alternately from left to right and then from right to left. When the coil is parallel to the magnetic lines of force, no current is generated. The alternating current so generated is collected by slip rings attached to the ends of the rotating coil and then transferred to an external circuit through metallic brushes.

Alternating current can be readily transmitted over long distances with minimum loss unlike DC. Any voltage drop along the way can be easily boosted using transformers. Also motors with high power can be designed using AC. Eddy current and radiation losses are the principal disadvantages of AC. 3 phase AC is generated in power stations, with each current out of phase by 120 deg to each other.

For a simple explanation about converters and inverters, visit this web page.

Five Easy Steps to Selecting the Right Switch

Although it is often one of the last components considered, selecting the correct switch is important when designing electronic equipment. Designers must be aware of the various options available in order to choose the most appropriate switch for any given application.
The procedure of selecting the correct switch can be summarized this way:

  • The requirements of the end user should be given consideration first
  • The engineering aspects like load, contact materials, terminal type, voltage, circuit type, mounting etc should be studied
  • Next the type of actuator should be decided
  • Standards like RoHS and similar government regulations must be complied with as well
  • Lastly, the switch chosen should be able to stand up to the rigors of the application. Environmental factors must be considered

When choosing a switch, you can ensure that the most appropriate switch is selected for the job if you take these factors into consideration.

What is Infrared?

What is Infrared?

The electromagnetic spectrum has waves of various wavelengths. Human eyes are capable to seeing the light that form a small part of electro magnetic spectrum. The waves with shorter wavelength as well are longer wavelengths than the visible spectrum are not visible. Infrared are waves that have longer wavelengths than the visible spectrum. The wavelengths corresponding to the Infrared waves are in between 750nm to 1mm.

Infrared waves cannot be seen but can be felt in the form of heat. Since the main source of infrared emissions is thermal source, so any thing that has temperature will emit Infrared emissions. Most of them are not noticed because they are not so strong. Higher is the temperature of the object, greater will be the Infrared emissions. Substances that seem cold such as a cube of ice also emit infrared.

Uses of Infrared:

  • Night vision: Infrared filters are utilized to filter 99 percent of the light of the visible spectrum and allow maximum infrared light to pass through them. This helps in viewing objects even in the dark based on their infrared emissions.
  • Thermo vision: Infrared emissions are utilized to find out the temperatures of distant objects. All celestial bodies emit strong Infrared emissions. These emissions are an easy way to study about the topography as well as climate of the celestial bodies.
  • Communication: Infrared transmission is an easy way to transfer data for a short distance. Infrared finds its application in remote controls in which the Infrared LEDs are utilized to emit radiations that are focused over the Infrared acceptors. The Infrared LEDs also find their application in movement sensors such as optical mouse used in our desktop.
  • IR LEDS

    IR LEDS

  • Spectroscopy: Infrared waves find their applications in analysis of the molecules.
  • Satellite images: Infrared imaging is utilized by satellites to send in the details regarding the weather and geography of a place.