AS ICT Unit 3

Describe the purpose & use of a proximity sensor

A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation (infrared, for instance), and looks for changes in the field or return signal. Can be used a reversing sensor for a car. Collision detection for robots Mobile phones have a proximity sensor, when you raise your phone to your ear, its screen will automatically go dark due to the feature, saving battery and making sure you don't press any buttons.

Describe one point calibration

A reading is taken from the sensor and compared with an already captured measurement (e.g. the reference standard). The difference between the two sensors is the offset of the sensor, code in the control device can be altered to include this offset. Useful to measurements which are linear and to check the performance degradation over time.

Explain what is meant by a 'smart home'

A smart home can use WSAN to control many devices in the home. Devices can be control via your voice (dialogue interface system) or via a smart phone. The Internet of Things (IoT) can allow devices to be control and monitored remotely such as control your heating via the Internet. Smart devices can be used to check device while outside the property such as check if you remembered to turn off the lights.

Describe the purpose & use of a sound sensor

A sound sensor detects sound waves through its intensity and converting it to electrical signals. It has a diaphragm which measure the vibrations and changes into current otherwise voltage. Security camera which are activated by noise. Dialogue communication systems like Alexa, Siri

Describe the purpose & use of a touch sensor

A touch sensor is a type of device that captures and records physical touch on a device and/or object. Capacitive touch sensor measures touch based on electrical disturbance from a change in capacitance. It consists of an electrode film on top of the glass panel that's conductively coated with a printed circuit pattern around the outer viewing area. Resistive touch sensor measures touch through responding to the pressure applied to their surface. It consists of two conductive layers and a non-conductive separator. Unlike the capacitive touch sensors, it's not multi-touch compatible. Can be used in touch screen devices on phones, interactive TVs Can be used to control a home appliance such as a cooker hob

Describe the inputs and outputs used to control of traffic flow

Active traffic management (ATM) is used to control congestion on a motorway. ATM implements a variable speed limit and reduces congestion by allowing the use of the hard shoulder. It will use an electromagnetic field sensor (inductive loop) position just below the surface of the road about every 500 meters. This is used to count the number of cars. A side-fire radar is used to measure the speed of the vehicles. If the motorway becomes congested, then the speed limit is lowered, and the hard shoulder is opened. CCTV can also be used to observe for occurrences such as accidents.

Explain the role of an actuator in a control system

Actuators are used to control a device such as a valve or a switch. They are used in a control system to control an output device. It turns an electrical signal from the microprocessor into a movement.

Describe the inputs and outputs used in a car park barrier

An inductive loop (electromagnetic field sensor) is buried below the surface of the road in front of the barrier. When a car passes over the top of the inductive loop it changes the magnetic field. The loop detects this and sends the data to a microprocessor where it is compared to a pre-set value, if it is greater than the pre-set value then the actuator will open the barrier using a motor. A second sensor is used to ensure that the barrier does not close until the car has cleared the barrier. It uses a light sensor, while the car is blocking the light emitted the barrier will remain open however once the light emitted is detected by the light sensor the barrier will close. Some carpark's issue a ticket to the driver on entry to the car park, the driver needs to enter a ticket into the machine\kiosk to pay for parking before leaving, the system records that they have paid. The ticket then needs to be entered into the barrier which checks whether the parking has been paid which will then uses an actuator and motor to open the barrier. The ticket is read using a barcode scanner. Some carparks using an Automatic Number Plate Recognition (ANPR). The user registers their number plate at a machine to pay for their parking. When they leave the car park the ANPR will read the number plate. It captures an image, uses an OCR to convert the image into text and then enters the number plate text into the system to check that the user has paid. If they have the barrier is opened.

Describe the purpose & use of a pressure sensor

Converts a force applied to its surface to generate electrical energy which is then converted into values that represented applied pressure. Can be used to measure pressure of a car on a certain spot to control a barrier. Weather stations uses a pressure sensor to measure atmospheric pressure

Describe the advantages of control technology

Created new jobs such as engineers and maintenance staff to build and fix the control systems. Burglar alarms can give people a sense of security they are less likely to be burgled. Smart home can be programmed to be energy efficient meaning that less energy is wasted. Computer controlled traffic lights can reduce the number of traffic jams. Smart home can aid disabled people to activate devices more easily. Smart devices in the home can allow people to have more leisure time which could be good for their mental health. Automatic systems for a greenhouse can run without human intervention and can create the optimum growing conditions, humans may forget to water the plants. Control systems can read many sensors at the same time and perform an action immediately which is difficult for a human to do.

Describe the purpose & use of an infrared sensor

Infrared sensors are a specific type of motion sensors that use infrared radiations. Passive sensor using infrared to detect the presence of energy. An active sensor uses microwaves; it detects changes in the reflection when the microwave bounces off objects. Security systems (burglar alarms), automatic doors, lighting, automatic barriers for car parks.

Describe the inputs and outputs used in a burglar alarm

Infrared sensors could be used to detect bodies present as they emit heat. Sound sensors could be used to detect sound an intruder may make. Pressure sensors can be placed on floors to detect whether anyone has stepped on a certain spot. The microprocessor will compare these values to set values in the program, if the levels are above the pre-set values then an alarm will be sounded. Lights can also flash or turn on to deter the intruder. Also some systems are hard-wired to the police to alert them that an intruder maybe present. The system needs to be activated for this to occur.

Describe the disadvantages of control technology

It has reduced number of jobs needs to perform actions. Less car park attendants are required. Smart home can make people lazy and less active which is not good for our health. Also we can become reliant upon the technology and if it breaks the device may not work. Cost of purchasing smart devices for the home is likely to be higher.

Describe the advantages of monitoring technologies

It is difficult for humans to take readings at frequent intervals. Computers can take readings consistently and are able to take more than one reading at a time. Computers can take readings for a sustained amount of time. 24/7 365 days a year without a break. It takes time for humans to draw accurate graphs whereas computers can produce them automatically after processing the data so that they are up to date. Computers are more accurate than humans and are not subjected to "human error".

Describe how wireless sensor and actuator networks (WSAN) are used.

It is made up of a group of networked sensors that communicate wirelessly. An actor is the name given to a group of actuators which collaborate to perform an action together. Some examples of a WSAN are smart parking which can alert a driver of how many parking spaces are available in a car park. Wireless sensor networks (WSN) only record\monitor the environment they take no action.

Describe the purpose & uses of a light sensor

Light sensors detect light and convert light energy to an electrical signal output. Once converted into electrical energy, the radiant energy within the infrared to ultraviolet light frequency spectrum source can then be measured. It is used to measure the amount of sunshine or UV. Can be used to adjust the brightness of a screen. Used to water crop when it is dark with automatic sprinklers. Weather stations uses a light sensor to measure sunlight

Describe the purpose & use of a temperature sensor

Measure temperature by assessing the amount of heat present. The working of a temperature meter depends upon the voltage across the diode. The temperature change is directly proportional to the diode's resistance. The cooler the temperature, lesser will be the resistance, and vice-versa. Weather stations uses a temperature sensor to measure ambient temperature Used in a central heating or air conditioning system to control the temperature of a room. Washing machines and dish washers measure the temperature of the water. Fridges and Freezers has temperature sensors which measure the temperature inside the machine.

Describe the purpose & use of an electromagnetic field sensor

Measures the change in the Earth's natural magnetic field caused by the presence of ferromagnetic object. Can be used to detect a presence of a car in a parking space. It can also be used to detect a car at a car park barrier.

Describe the purpose & use of a humidity sensor

Measures the humidity and temperature all in one unit. The moisture in the air to calculated by using a light sensor and a light emitter as the amount of light transmitted depends upon the moisture in the air. Agriculture - Greenhouse will use moisture and humidity sensors to grow crops. Moisture of soil can be monitored and control to optimise growing conditions Weather stations - humidity levels allow them to predict weather patterns Wine Cellars - The incorrect humidity can ruin wine.

Describe the disadvantages of monitoring technologies

Monitoring equipment can be expensive to buy and maintain. It can be difficult to program the computers to interrupt the results. Sensors can deteriorate after a period of time which may lead to inconsistent results. The sensors may need recalibrating.

Explain the differences between a monitoring system and a control system.

Monitoring systems only record data whereas a control system performs an action Monitoring systems don't have output devices such as motors or actuators whereas control systems do have outputs such as motors or actuators. Monitoring systems record the data to be analysed later while control systems act in real time

Describe multipoint calibration

Multipoint calibration is used when the sensors that are not linear over the measurement range require some curve-fitting to achieve accurate measurements over the measurement range. At least three known temperatures are required.

Describe the purpose & use of an ultrasonic sensor

Sends out a soundwave at a frequency greater than what is audible to a human, the sensor receives the soundwaves which bounce\reflect from an object. It measures the amount of time taken for the soundwaves to be sent and returned. Can be used a reversing sensor for a car.

Characteristics of a Control System

Sensors are input devices which are used to record data. A sensor will constantly take readings of its surrounding area. The data which is read is analogue and for it to be processed by a computer system it needs to be converted to a digital signal, this is where an Analogue to Digital Convertor is used (ADC). The digital data is sent to a microprocessor (CPU) which compares the values read against a pre-set value and it decides if an action is required. It the value read is outside the acceptable range and action is taken. This action will be an output device (like an alarm (speakers), a flashing light, to start a motor etc). It will use an actuator to trigger the output device.

Explain the importance of an ADC (Analogue to Digital convertor).

Sensors read analogue data (waves) and the microprocessor only understands digital data (binary). An ADC is needed in every monitoring and control system as the analogue signals need to be converted to digital signals for the data to be compared and processed.

Describe the purpose & use of Oxygen, Carbon Dioxide, PH and Turbidity sensors

Sensors used to measure the environment and water pollution. Oxygen sensors measure the amount of oxygen in soil or water. Carbon dioxide sensors measure the amount of carbon dioxide in the air or water, they are a modified infrared sensor. pH sensors measure the amount of acidity in the soil or water. They work similar to a simple battery and generate electricity depending upon the number of hydron ions in the solution. Turbidity sensors measure the amount of cloudiness in the water.It is a light sensor which is placed at a right angle to the light emitter.The greater number of particles in the water the more light is reflected off them and read by the light sensor.

Describe what type of sensors are used to measure environment monitoring.

Sound sensors may be used to monitor the amount of noise pollution in a city, e.g. the noise from cars. pH, humidity (moisture) and temperature sensors could be used to measure the quality of the soil in gardens, farms or greenhouses. Oxygen and carbon dioxide sensors can be used to measure air quality in cities, this can be used to warn people with health issues Monitoring ultraviolet from the sun can be used to warn people about the risk of sun burn.

Describe the inputs and outputs used in an automatic greenhouse.

Temperature sensor are used to measure the temperature, this temperature is compared against a pre-set value entered for optimum growing conditions. If the temperature is too high then the actuator will trigger a motor to open a window and turn off the heater, if the temperature is too low the actuator will trigger a motor to close the window and turn on the heater. Moisture sensor are used to measure the moisture of the soil, this reading is compared against a pre-set value entered for optimum growing conditions. If the moisture is too high then the actuator will close a valve to stop the sprinkler, if the moisture is too low the actuator will open the valve to turn on a sprinkler. Light sensors measure the amount of light in the greenhouse. Two pre-set values are entered one which is used to compare the light level during the day, if the light during the daytime becomes low, a light will be turned on in the greenhouse. However, at night the light needs to be turned off so the second pre-set value (which will be lower than the first) is used to judge when it is dark to turn the light off.

Describe the sensors used at a weather station

Temperature sensors are used to measure the ambient temperature (surrounding air temperature) Pressure sensors are used to measure the atmospheric pressure which is the air pressure above us. High pressure leads to sunny weather while low pressure leads to wet and windy weather. Humidity sensor are used to measure the absolute and relative humidity. Absolute humidity is the moisture in the air without considering the temperature while relative humidity considers the temperature. It is used to predict the likelihood of rain or snow. Light sensors are used to measure the number of hours of sunlight. A tipping bucket and reed switch are used to measure rainfall. When the tipping bucket reaches a certain amount of rainfall it will tip the water out, a reed switch is activated which will send a signal to the microprocessor, which records the number of times the bucket has tipped. Wind speed and direction is also measured.

Describe the type of sensors used to monitor water pollution

Temperature sensors can be used to measure the change in the water PH sensor can be used to measure the acidity or alkalinity of the water A light sensor can be used to measure the turbidity. It a measurement of the amount of light that is scattered by material in the water when a light is shined through the water sample.

Describe the inputs and outputs used to control traffic lights

The system uses an inductive loop to count the number of cars travelling in each direction. The values are sent to a microprocessor and compared to pre-set values. The microprocessor changes the traffic light timings based upon the amount of traffic in each direction.

Describe the inputs and outputs used in an air conditioning system

The user turns the system on and inputs a pre-set value for the temperature to be. The microprocessor reads the temperature using a temperature sensor. If the read temperature is lower than the pre-set value then the actuator will open a valve to turn the fans off. If the temperature is higher than the pre-set value the actuator will close the valve to turn the fans on.

Describe the inputs and outputs used in a central heating system

The user turns the system on and inputs a pre-set value for the temperature to be. The microprocessor reads the temperature using a temperature sensor. If the read temperature is lower than the pre-set value then the actuator will open a valve to turn the heating on. If the temperature is higher than the pre-set value the actuator will close the valve to turn the heating off.

Explain why it is important that the sensors are calibrated correctly.

To ensure accuracy of the reading of the sensor. Sensors are not perfect and may produce slightly different readings. Sensors age over time and may need recalibrating. The sensor is only one component of the measuring system, it may include an ADC which might produce an offset. Exterior conditions may affect the reading the sensor gives.

Describe two point calibration

Two measurements are taken one at the low end (RawLow) and one at the high end (RawHigh) and then take two more readings with the reference instrument (ReferenceLow and ReferenceHigh). The low end could be measuring the temperature of iced water and the high end could be measuring boiling water. Calculate "RawRange" as RawHigh - RawLow. Calculate "ReferenceRange" as ReferenceHigh - ReferenceLow CorrectedValue = (((RawValue - RawLow) * ReferenceRange) / RawRange) + ReferenceLow