1. Control
GCSE ICT

2. Input / Output, Processing
Inputs Devices
Processing
Output Devices
Sensors – temperature , heat, sound, Humidity, acidity, moisture, light, movement, pressure etc
Comparing data – between pre-defined set limits e.g. upper and lower limits
Actuator – motor that could control a barrier
Lights – e.g. warning lights
Buzzers – audible output e.g. an alarm
Robotic Arm – move a device to a different place
Heaters, Water pumps, Speakers, LCDs etc

3. Control Feedback Loop Feedback Input Process Output Control Program
Analogue to digital conversion
Data such as pressure, light and temperature is analogue data. Computers can only work with digital data.
An interface box or analogue to digital converter (ADC) is needed to convert the analogue data from the sensors into digital data the computer can process.
Feedback - Where input from sensors is used to change output in a control program, then the output is fed back to modify the input.

4. Input / Output, Processing - Greenhouse
Inputs & Feedback
Processing
Outputs
Temperature Sensor – measures air temperature
Feedback – turn on heater, open windows
Air humidity sensor – measures air humidity
Feedback – spray mist into the air too low, open windows too high
Soil Moisture sensor – measures soil moisture
Feedback – add water is too dry
Light Sensor – measures light in greenhouse
Feedback – close shades if light level too high, turn on artificial light if length of day too short
Compare temperature of greenhouse of upper and lower limits and select appropriate controls
Compare humidity of greenhouse of upper and lower limits and select appropriate controls
Compare the soil moisture of greenhouse of upper and lower limits and select appropriate controls
Compare the light levels in the greenhouse of upper and lower limits and select appropriate controls
Heaters – to heat the air
LCD – Control Panel
Displays time, Current Temperature, Humidity, Light readings, set limits
Lights to provide artificial light
Motors/Actuators to open and close windows
Water Pumps to spray water mist into the air

5. Control System Applications
Central Heating Systems
Burglar Alarms
Automatic doors
Traffic Control Systems
Car Parking Systems
Robotics