Technology News

Samrt Cane to Help Blind:

A ' Smart' cane has been developed by the students at Central Michigan University that helps the blind in Moving around by themselves easily.

The Cane uses radio frequency indentification (RFID) to detect obstacles and alert the user on where and how to navigate while walking. It is equipped with an ultrasonic sensor and works in tendem with a navigational system inside a bag worn by the user. The cane requires RFID flags mounted along the path to help the user in reaching his destination.

A Speaker on the bag's strap alerts the user of an obstacle coming in his way and tells him where to walk. For people who can't hear, a special glove vibrates different fingertips to provide direction on where to walk.

Robots Assist doctors in life-saving operations:

Robots are helping doctors to treat soldiers in combat zones from faraway locations. In these operations,the robot is mounted with a high-tech camera and controlled from another region via  a laptop and remote joystick. The robot can move easily because of the sensors located on its torso, which help it to identify obstacles. The camera on the robot captures images of the patient from every angle and a zoom oprion allows doctors a close-up view of their distant patients.

THe technology has been incoporated by Dr. Kevin Chung, in-charge of the burn intensive care unit at Brooke Army Medical Center in San Antonio, Texas, to treat patient.

Robots could Turn Dangerous:

Robots could be dangerous to human beings. A situation which is now limited to only sc-fi films, such as the TErminator series and The Matrix, could become true.

Leading scientists warn that man-kind might lose control over computer-based systems that carry out a growing share war to chatting on the phone, and have already reached a level of indestructibility comparable with a cockroach.

Too much time is being spent on developing artificial intelligence and too little on robot safety.We'ar rapidly approaching the time when new robots should undergo tests, similar to ethical and clinical trials for new drugs, before they can be intruduced. said Alan Winfield, a professor at the University of the West England.

Switches

Switches are used to control the flow of current in a circuit. Current flows when the switch contacts come together. We say that the switch is closed, or contact is made. Current can not pass through the switch when the contacts are apart. We say that the switch is open, or contact is broken. There are many different types of switch, used for different purposes. Here we describe a few of the most useful types.

Toggle switch :


A toggle switch is a basic switch, operated by a toggle lever that can be pushed up or down. By convention, the down position is the ‘on’, or ‘closed’ , or ‘made’ position. The toggle switch in the photo has its toggle lever up. Behind the
lever is a threaded dolly with a large nut. This is for mounting the switch in a circular hole cut in a panel.

At the rear are two terminal tags to which the connecting  wires are soldered. This switch is a heavy-duty type, rated to
switch currents as large as 10 A and 250 V AC. Heavy-duty toggle switches are often used for switching the mains power supply to appliances and equipment. However, they can be used for switching smaller currents too.

This miniature toggle switch is suitable for mounting on a control panel. It is able to switch 1.5 A at 250 V AC.

The larger toggle switch has two solder tags, showing that it has single-pole, single throw contacts (SPST). Its symbol shows how it works. It switches a single circuit and it is either open or closed. The miniature toggle switch has single-pole, double-throw contacts (SPDT). The centre tag is common and can be switched into contact with either of the other tags. Such contacts are called changeover contacts.

Microswitch

The ‘micro’ part of its name does not mean that the switch itself is necessarily small. It means that the operating button moves only a small distance.

The switch is very sensitive. A light pressure on the lever causes the switch to click over from one position to the other. Most microswitches have SPDT contacts so that they can either switch something on or switch something off, perhaps both at the same time.

The contacts on a microswitch are sprung so that normally the common contact connects to what is called the normally closed (n.c.) contact. The third contact is the normally open (n.o.) contact.
Microswitches are used where a switch has to be operated mechanically. For example, a microswitch is mounted inside a cupboard, so that the lever is held down when the door is closed. Its common and normally closed contacts are wired into a lamp circuit. When the door is closed, the contacts are open and the lamp is off. When the door is opened, the contacts close and the lamp is switched on.

Reed switch :

This consists of two springy metal contacts (the reeds) sealed into a capsule with their ends over-lapping. Normally the contacts are open. In a magnetic field, the reeds become magnetised. Their north and south poles attract each other. The reeds come together and make  contact. When the field is removed, their springiness moves the reeds apart. apart.

Larger reeds switches can switch mains currents of up to 2 A.

The magnetic field may be provided by a permanent magnet or by a coil. For example, in a security system, a reed switch is mounted on a door-frame. A magnet is mounted on the door. When the door is shut, the magnet is near to the switch. Contact is made. If the door is opened, the magnet is moved away from the switch. The contacts open, breaking the circuit

and triggering an alarm. If the reed switch is operated by a coil wound round its capsule, the switch acts as a relay.

Tilt switch :

The switch closes when it is placed in its normal vertical position. The switch opens when it is tilted. If a switch is attached to a movable part of a machine, it can be used to detect whether that part is in the correct position or not.

Membrane switch :
When the button is pressed, a flexible, conductive plastic film below the button is pressed down. It bridges the gap between two metal contact pads, so that current can flow from one to the other.

Membrane switches are available as single switches or as key-pads of the type used in pocket calculators and security systems.

Push switches :

A push switch is operated by pressing a button. There are two types of action. Most switches are push-to-make (or PTM)
switches. Pressing the button pushes the contacts together and the switch closes. The other type are push-to-break (or PTB) switches. The contacts are normally closed but are forced apart when the button is pressed.

Either type of switch may be momentary or latching. A switch that is momentary acts only for as long as the button is pressed. When the button is released, the switch springs back to its normal state.

In a latching switch, the button stays down when pressed. The contacts remain closed or open, depending on the type of switch. You need to press the button again to return the button to its normal state.

Push buttons are used for a wide variety of control purposes, and may be used for power switching for lamps, radio sets and other appliances.

Rocker switches:


These are similar in action to toggle switches and are used for the same purposes. The difference is that they are operated by a rocker.

Slide switches :


These have uses similar to toggle switches, but they are operated by a sliding knob. The slide switch in the photo is a SPDT switch. The common connection is made to the central terminal.

DPDT switches ;

Toggle, rocker and slide switches are also made as double-pole double throw versions. This gives two separate switches within the same unit, but operated together.
DPDT switches can be used to switch on two circuits at the same time. They may also be wired into both the live and the neutral mains lines.
When the switch is off, the appliance is completely isolated from the mains. DPDT switches are often used with electric blankets for safety.

Rotary Switches:

Rotary switches are used for switching one line to any one of several other lines. Often several such switches are  combined in one unit.

The switch has one or more rotating contacts surrounded by a ring of usually 12 stationary contacts. Switches are produced with several different arrangements of contacts. These are 1-pole-12-way, 2-pole-6-way (see drawing), 3-pole-4-way and 4-pole-3-way. They are used for functions such as s e l e c t i n g wavebands on a radio receiver, or selecting the
me a s u r e m e n t ranges of a multimeter.