Data logging and control software

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Data logging and control software

Sensors: used to detect and measure physical quantities. Examples:

  • Temperature/heat sensors - can be used to control a heating system
  • Light sensors - detect the brightness of light
  • Sound sensors - measure the loudness of a sound
  • Pressure sensors - measure air pressure
  • Humidity sensors - moisture in the air
  • Passive infrared sensors (PIRs) - used to detect movement

Data logging: readings are taken regularly over a period of time using sensors

  • readings taken automatically - cheaper than employing person to do this
  • can set the logging period - total time over which the readings will be collected
  • can also set the logging rate (logging interval) - determines how often the readings are taken
  • sensors can be put in remote locations - can put them anywhere in the world and the data can be sent back wirelessly and even using satellites
  • data sent can be stored and processed by a computer
  • data can be analysed - calculations e.g, mean, mode, median - data can be processed using a spreadsheet package

 

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Sending data to a computer:

  • use wires to connect the data logger to the computer
  • use wireless usually bluetooth

ADV OF DATA LOGGING

  • readings always taken at exactly the right time
  • do not need anyone to take the readings
  • no human error when taking readings
  • the system does not forget to take a reading
  • readings can be taken faster
  • can be situated in inhospitable places e.g, North Pole
  • readings can be taken 24/7

DISADV OF DATA LOGGING:

  • equipment is expensive
  • equipment malfunction can cause wrong readings
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Controlling devices

Using a sequence of instructions to control devices:

FD distance

LT angle

RT angle

Main components of a control system:

  • Sensors - input devices that send data to a processor
  • Computer/processor - uses a control program to decide what action to take when it recieves data from the sensors, sent to the output device
  • Output devices - controlled by control sigals

NON-FEEDBACK CONTROL SYSTEMS:

  • no way of detecting whether it has actually moved through the correct angle
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SIMPLE CONTROL SYSTEMS:

  • burglar alarms
  • electronic toys and games
  • automatic doors - motion sensors, signal sent to actuator (electric motor) to open the door, door will only close if the system detects that there is no one in the vicinity
  • smart meters - small devices that give instant info about amount of gas and electricity they are using
  • car parking systems - signs indicating how many spaces are left are controlled by a central computer that uses data from how many cars have entered the car park and how many have left
  • traffic control systems - aims are to improve traffic flow, improve driver and pedestrian safety by reducing frustration, make sure that any delays in a journey are kept to a minimum, reduce the risk to the environemnt caused by fumes from waiting traffic, reduce the use of fossil fuels

OUTPUT DEVICES CONTROLLED BY CONTROL SYSTEMS: input signals from sensors are passed to the computer where the control signals are passed to output devices to control them

  • actuators - devices such as motors react according to signals given by computer
  • stepper motor - a motor that turns in a series of small steps
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  • bells/sirens - control systems where an alarm signal needs to be sounded
  • heaters/coolers - used for controlling the temp of an environment
  • light - floodlights or flashing lights used in control systems

ROBOTICS:

  • used for manufacturing
  • picking and packing goods in large warehouses
  • do tasks humans hate e.g, mowing the lawn or vacuuming the floors
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  • bells/sirens - control systems where an alarm signal needs to be sounded
  • heaters/coolers - used for controlling the temp of an environment
  • light - floodlights or flashing lights used in control systems

ROBOTICS:

  • used for manufacturing
  • picking and packing goods in large warehouses
  • do tasks humans hate e.g, mowing the lawn or vacuuming the floors
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Control-feedback loop

Main components of control-feedback loop

  • input can be given by the user as an instruction, sensed by sensors that send signals to the computer
  • input data gathered by input device and sent to processor to processing
  • processor works within data and a stored program to work out what it needs to output
  • some of the output is fed back to the input using the feedback loop

CONTROL PROGRAM: the step-by-step instructions that control the output devices

FEEDBACK: where the output from a system directly affects the input

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