Cambridge IGCSE Revision Question - Computer Applications
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What is the main difference between monitoring and controlling of a process?
Monitoring a process: • Sensors send data • Data converted to digital data (using ADC) • Computer analyses/compares data • If outside the range (when compared to stored values) . . . • . . . it sends a signal to sound alarm or produce warning message on a screen. Controlling a process: • (First four lines are the same as above) • . . . it sends signals to actuators • Signals converted to analogue using DAC • Pumps/va lves (etc.) are opened/closed (etc.) to alter the process conditions • The output affects the next input.
Describe how a computer and sensors are used to monitor the greenhouse environment; the temperature m ust be between 25°( and 30°( and the soil pH must be between 4 and 5.
• Data gathered from temperature and pH sensors • Signals sent to ADC where they are converted to digital • Information is sent to the computer where it is compared to pre-set/stored values • If the temperature 30°C, a signal is sent by the computer to the motors to open the windows (again DAC and actuators used) and to switch off the heaters • If the temperature is between 25°C and 30°C, no action is taken • If the pH 5, a signal is sent by the computer to open valves to add acidic water (again use of DAC and actuators) • If the pH is between 4 and 5, no action is taken • In all cases, the output from the system will affect the next input to the system • Alarm is sounded if there is an error in the system • Monitoring and control continues until system turned off.
Name three other sensors and describe three different applications which use these sensors.
Light sensor - automatic doors in a hotel Acoustic sensor - picks up sounds, for example,a burglar alarm Infra red sensor - counting items every time the beam is broken.
Monitoring and controlling processes
Many monitoring and control applications do not use a computer system; a microprocessor is used instead but the methodology and the outcome are the same.
Actuators
Actuators are used in many control applications involving sensors and computers or m icroprocessors. They are usually electromechanical devices such as a motor, relay or solenoid. Actuators can be digital (solenoid) but others require a digital to analogue converter (DAC) since the actuator needs an electric current/voltage to operate a motor or a valve, for example.
Robots are being used to spray some metal components with paint. Describe: (i) Two problems the robots might encounter when spraying these metal components. (ii) How these problems could be overcome.
(i) Two problems - out of paint - component is m issing - something is obstructing the paint spray gun. (ii) Use of sensors to detect out of paint, item is in the correct position, something is obstructing the spray gun, etc Use of CCTV/cameras to show the status of the process (e.g. these can check paint surface of a car for imperfections).
In general, what are the advantages and disadvantages of using robots rather than using human workers in a manufacturing company?
Advantages: Can work in conditions hazardous/unpleasant to humans; They can work non-stop (no breaks); Less expensive in the long run (no wages required); More productive (takes less time to do a task than a human); More consistent (everything is always made to the same standard); Removes the need for humans to do boring/ repetitive tasks; Less factory costs (can reduce heating, lig hting levels, etc.). Disadvantages: Difficulty dealing with non-standard situations; Can lead to unemployment; Possible risk of deskilling; Production process can be more easily moved to ‘less expensive’ countries.
A computer system has been set up with a graphical user interface and windows environment. Icons are used on the screen to identify applications. What devices could be used to select and open the appropriate applications?
• Pointing devices such as mouse - Touch screens
A command l ine interface could have been offered instead of G U I . What are the relative benefits and drawbacks of using both G U I and CLI to communicate with the computer system?
Com mand line interface: Direct communication with computer; Increases flexibility (G UI is very restricted); Graphical user interface: No need to understand how computers work; Much quicker/easier to find and open applications rather than have to type in a series of instructions.
A mobile robot is used to enter harsh environments to take samples and to carry out maintenance work. (a) The mobile robot is fitted with sensors. r.==�:-L—— sensors � �wheel’ The robot is also equipped with an on-board computer. Describe how the sensors and computer are used to guide the robot as it travels remotely. It needs to travel straight or go around corners without bumping into anything.
(a) - Sensors pick up proxim ity of objects Sensors pick up information from surroundings to make sure trave l ling Straight or can turn when path bends - Data is sent to the computer - This data is analysed by the computer - Signals sent to wheels/motors to turn vehicle as needed (also use of DAC and actuators).
Name two types of mobile screen technology. Give two advantages and two disadvantages of each of the chosen technologies.
Capacitive Benefits - this is a medium cost tech nology - screen visibi l ity is good even in strong sunl ight - it permits multi-touch capability - the screen is very durable; it takes a major impact to break the g lass Drawbacks - allows only the use of bare fingers as the form of input; although the latest screens permit the use of a special stylus to be used Infra red Benefits - both systems al low mu lti-touch capabilities - the optical system allows the use of bare fingers, gloved fingers or stylus for input - both systems have good screen durability; it takes a major impact to break the glass Drawbacks • it is a relatively expensive technology • heat sensitive system only a llows bare fingers to be used for input (gloved fingers or stylus don’t work) • both systems (optical and heat sensitive) have fairly good screen visibility in strong sunlight. Resistive - this makes use of an upper layer of polyester (a form of plastic) and a bottom layer of g lass - when the top polyester layer is touched, the top layer and bottom layer complete a circuit - signals are then sent out which are interpreted by a microprocessor; the calculations determine the coordi nates of where the screen was touched. Benefits - it is relatively inexpensive technology - it is possible to use bare fingers, gloved fingers or stylus to carry out an input operation. Drawbacks - screen visi bility is poor in strong sunl ight - it doesn’t permit mu lti-touch capability - the screen durability is only fair; it is vul nerable to scratches and the screen wears out through time
A chemical process is being monitored using temperature sensors and pH sensors. These sensors send data to a microprocessor. If the tem perature in the process drops to below 50°( then a heater is switched on and if the acidity rises to a pH of 5, then a valve is opened to admit more acid (pH must be kept below 5). Describe how the sensors and microprocessor are used to control the chemical process.
• sensors contin ua l ly send data to the microprocessor if the output from the sensors is analogue, then the data is converted to digital, using an ADC, before it is sent to the microprocessor • the microprocessor contains optimum temperature and acid/pH val ues (or they are stored on a storage device connected to the microprocessor) • if the temperature reading is = 50°( then no action is taken • if the pH reading is > 5, then a signal is sent to a valve to open and allow acid to enter chemical process • if the pH