How Can Computers Control Things?
A normal PC has no senses, but we can give it some: We can connect sensors to it...
A sensor is a device that converts a real-world property (e.g. temperature) into data that a computer can process.
Examples of sensors and the properties they detect are...
|Sensor||What it Detects|
|Light||Light / dark|
|Pressure||Pressure (e.g. someone standing on it)|
|Moisture||Dampness / dryness|
|Water-level||How full / empty a container is|
|Proximity||How close / far something is|
|Switch or button||If something is touching / pressing it|
A normal PC has no muscles, but we can give it some. In fact we can give it the ability to do lots of things by connecting a range of actuators to it…
An actuator is a device, controlled by a computer, that can affect the real-world.
Examples of actuators, and what they can do are...
|Actuator||What it Can Do|
|Light bulb or LED||Creates light|
|Cooling Unit||Decreases temperature|
|Motor||Spins things around|
|Pump||Pushes water / air through pipes|
|Buzzer / Bell / Siren||Creates noise|
Making Decisions (The Process)
- Check the data from the sensors
- If necessary, turn on/off one or more of the actuators
- Go back to step 1
Where is Computer Control Used?
- Washing machines
- Air-conditioning systems
- Programmable microwave ovens
- Modern cars have engines, brakes, etc. that are managed and controlled by a computer
- Most factory production lines are computer-controlled, manufacturing products with little or no human input
- Traffic lights are switched on and off according to programs running on computers which manage traffic flow through cities
However using computers to manage these systems has brought many benefits...
Why Use Computers to Control Thing?
- Computers never need breaks - they can control a system without stopping, all day, every day
- Computers don’t need to be paid. To buy and install a computerised control system can be very expensive, but, in the long-term, money is saved by not having to employee staff to do the work
- Computers can operate in conditions that would be very hazardous to human health, e.g. nuclear power stations, chemical factories, paint-spraying areas
- Computers can control systems far more accurately, and respond to changes far more quickly than a human could
An Example Control System - An Automated Greenhouse
- A light sensor to detect how much light the plants are getting
- A temperature sensor to see how cold/hot the greenhouse is
- A moisture sensor to se how wet/dry the soil is
- Lights to illuminate the plants if it gets too dark
- A heater to warm up the greenhouse if it gets too cold
- A water pump for the watering system
- A motor to open the window if it gets too warm inside
- Check light sensor
- If it is dark, turn on the lights
- If it is not dark, turn off the lights
- Check temperature sensor
- If it is too cold, turn on heater and use motor to close window
- If it is too warm, turn off heater and use motor to open window
- Check the moisture sensor
- If soil is too dry, turn on the water pump
- If soil is too wet, turn off the water pump
- Go back to step 1 and repeat