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

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

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

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

• 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

• 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

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