2 ObjectivesTrue control system is when the computer is controlling the output dependent on information from sensors about what is happening.Be able to describe a number of uses, giving the hardware and software requirements.Be able to describe the applications that these uses can be put to.Computers can control systems far more accurately, and respond to changes far more quickly than a human could
3 IPO (INPUT PROCESS OUTPUT) What is the role of the processor in any control system?
4 What is a control system? Uses microprocessors or computers to control certain physical conditionsSensors take measurements, then A/D converter converts them into digital signalsThe measurements are compared to stored (predefined) valuesProcessor makes a decision based on the comparisonControl output devices will be used
5 Examples of control systems Turtle Graphics (LOGO)Control of Lights and LampsTraffic Control SystemControl of Washing MachinesRoboticsBurglar AlarmsCentral HeatingVideo RecordersMicrowave OvensControl of Automatic CookersCentral Air ConditioningComputer-controlled Greenhouses
6 Usually measured by Sensors Physical conditions (variables) that are controlled by computer/microprocessors include:TemperaturePressureHumidityLightMoisture etc
10 Computer-Controlled Greenhouse ADCA light sensor to detect how much light the plants are gettingA temperature sensor to see how cold/hot the greenhouse isA moisture sensor to se how wet/dry the soil isLights to illuminate the plants if it gets too darkA heater to warm up the greenhouse if it gets too coldA water pump for the watering systemA motor to open the window if it gets too warm inside
11 IPO Computer-Controlled Greenhouse InputsProcessesOutputsLight SensorSensors monitor amount of light , moisture, temperature continuouslyLightMoisture SensorAnalogue data from sensors converted to digital using ADCWater PumpTemperature sensorTemperature compared to preset range/valueHeaterSignal sent to turn on heater and use motor to close window if too coldMotorSignal sent to turn off heater and use motor to open windows if too warmSignal to actuator to turn water pump on if soil dry or off is soil is moist
12 Air conditioningSensors are needed to monitor temperature (continuously)Microprocessor compares the temperature with a preset value/rangeDepending on result microprocessor causes the fan motor to speed up or slow downFan motor switched on or off
13 IPO Central Air Conditioning InputsProcessesOutputsButtons/touchscreenSensors monitor temperature continuouslyLED displayContact switchAnalogue data from sensors converted to digital using ADCFanTemperature sensorTemperature compared to preset range/valueBuzzerPressure sensorSignal sent to actuator to switch fan on or off
14 Closed Loop system Output directly affects the input No human intervention is necessaryGood for situations where control is required 24/7, or in a dangerous/difficult environment
15 Refrigeration Sensors continuously monitor temperature Microprocessor compares the temperature with a preset value/rangeDepending on result microprocessor causes the fan motor to speed up or slow downFan motor switched on or off
16 IPO Refrigeration Inputs Processes Outputs Contact switch (door) Sensors monitor temperature continuouslyLED displayPressure sensor (door)Analogue data from temperature sensor converted to digital by ADCCompressorNumber pad or dialTemperature compared to preset range/value input by userBuzzerTemperature sensorSignal sent to actuator to switch compressor on if temp is too highSignal sent to actuator to switch compressor off if temp is OK
17 Central heatingSensors are needed to monitor temperature (continuously)Microprocessor compares the temperature with a preset value/rangeMicroprocessor controls two actuatorsone opens gas valves in the boilerthe other switches the pump on
18 IPO Central Heating Inputs Processes Outputs Touch screen Sensors monitor temperature continuouslyLED displayNumber pad or dialAnalogue data from temperature sensor converted to digital by ADCRadiatorsTemperature sensorTemperature compared to preset range/value input by userSignal sent to actuators to switch pump on & open valves if temp is too lowSignal sent to actuator to switch pump off/close valves if temp is OK
19 Automatic Cooker (Microwave Ovens are very similar, more features, most can be set to turn themselves on and off at particular times)2 User inputs:Desired temperatureLength of cooking timeSensor measures the temperature in the cookerMicroprocessor controls a heating element to keep the temperature constantMicroprocessor controls a buzzer to inform the user when the time is up.
20 IPO Automatic Cooker Inputs Processes Outputs Touch screen/Keypad Sensors activatedTemperature SensorChecks if temperature greater than the temperature from the sensorBuzzerTimerHeaterAnalogue data from sensors converted to digital by ADC
21 Burglar AlarmUser inputs a code to set the alarm when they leave the house and a code to stop the alarm being triggered when they re-enter the houseDetects when a door or window is open using a simple magnet and contact switchIf the movement sensor senses something, the computer can immediately decide what to do
22 IPO Burglar Alarm Inputs Processes Outputs Touch screen/Keypad Sensors activatedLight SensorChecks if lights have been turned onBuzzer/Alarm activatedMovement Sensor (senses infra-red light changes)Detects if something is moving within a certain rangeMagnet/Contact SwitchChecks if doors/windows are openAnalogue data from sensors converted to digital by ADC
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