Computers In Control

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Selected and compiled by Muhammad Ume Bin Mujeeb   Class IX The City School

When people think of computers, they usually think of them being used in offices for administrative purposes. What many people don’t know is that computers can do almost an endless variety of other tasks including controlling devices and other things.

We have all read about robots in stories. They can walk, talk, reason with humans and occasionally go berserk. The robots in these stories are far removed from the robots in reality.
Actually, Robots are used because they reduce labor costs, improve the quality of finished products, and perform tasks continuously along with a number of other advantages.


Robots on the move
When robots start to move from place to place, there are several problems to solve.
1. How are robots able to navigate themselves?
2. How do robots stop colliding with each other and other objects?
3. How is the power provided?


How to solve these problems?
To allow robots to move properly, tracks are provided which are set into the floor and the robots follow these. This type of system is used in factories, where movable robots are used to move materials along the production line, and also in warehouses where robotic forklift trucks move goods. The robots also keep a record of the distance they have travelled and the angles they have turned through, so that they always know there exact position. What would happen if a person stood in the way of one of these moving robots or another robot dropped something in its way? On each robot there is an ultrasonic detector which emits a beam of infrared radiation. If anything gets in the way of the beam, the robot just stops.  Power is usually provided by batteries. When the batteries need recharging, the robots automatically go into a place where the batteries can be recharged.


Components used to control things
Using sensors
Sensors are used to detect various physical quantities, such as temperature, pressure, sound and light. The sensors are connected to a computer through an interface, and with special software the physical quantities can be displayed in a variety of ways on a computer screen. Some sensors are described below.


Mercury tilt switch
If a device is tilted or moved, a blob of mercury in the switch touches the contacts and completes a circuit. Such a switch can be used in a pinball machine to detect whether someone is tilting it. It could also be used to trigger an alarm in a vending machine.


Light sensor
A light sensor has many uses. For instance, it can be used to detect low light levels so that street lighting is turned on. It could also be used to detect the light reflected from a barcode.


Push switch
You might find a push switch being used to turn on the interior light inside a car when the door is opened. You could also use one for detecting when the fridge is opened, so that a light is switched on.  


Temperature sensor
One of the most common sensors is a temperature sensor. These are used, for example, in central heating systems to keep the temperature of a house constant.


Sound sensor
Environmental health officers could use sound sensors to record the level of sound coming from factories, shops and houses etc.


Proximity sensor
A proximity sensor is made in two halves. If the halves are moved away from each other, a signal is activated. You often see these sensors on windows, so that if the window is opened, the two halves of the sensor are separated and an alarm is activited.


Position sensor
A position sensor detects the angle of a spindle. It could be used to feedback the position of a robot arm.


pH sensor
A pH sensor is used to find out how basic or acidic a solution is.


Humidity sensor
A humidity sensor is used to determine the amount of moisture present (in the air or perhaps in soil).  


Output devices
There are devices which respond to the instructions given by a computer. Some of them are described below.


Actuators are hardware devices, such as motors, which react according to signals given to them by computers. An actuator motor, for example, would be used to open a window in a greenhouse when it gets too hot.


Stepper motor
A stepper motor, as the name suggests, is a motor which turns in a series of small steps. Stepper motors generally look fatter than ordinary motors and have several wires coming out of them. Pulses sent from the computer instruct the motor to turn through a required angle. Stepper motors can also be speeded up or slowed down and operated in forward or reverse direction. Stepper motors are used in robotic arms.


Example of a usage of sensors
The medical condition of a patient in an intensive care unit (ICU) can be continually monitored using sensors connected to the patient. Respiration, blood pressure, temperature, and electrical activity of the heart and pulse can all be measured by sensors. A computer is used to continually monitor the results from the sensors, and if the patient’s condition changes suddenly or values exceed given thresholds then an alarm is sounded to alert medical staff.