1. Monitoring and Control

2. A few definitions
Sensors: are devices used in monitoring device which measures some physical quantity and sends signals back to the processor.
ADC – Analogue to Digital Converter
converts signals in analogue format to digital format

3. A few definitions DAC – Digital to Analogue Converter
converts digital signals to analogue format
Actuator – It a device that can produce a movement when given an electrical signal. It receives the control signals and converts them into movement e.g it can be used to open/close valves

4. Monitoring
sensors will gather information and send to a ADC, which will convert analogue signals from the sensor to digital signals so that the computer can “understand”
Computer will compare incoming data with data values stored in memory
will warn user in the form of sound(siren, beep sound)

5. sensor
ADC
Analogue
signal
Digital Signal

6. Control
computer will compare incoming data from sensor to stored values in memory
computer will send digital signals to a DAC
DAC will convert digital signals into analogue signals
DAC will send converted signals to an actuator to perform an operation e.g turn on/off valves

7. Check values from sensor to stored values in memory
Analogue
signal
Turn ON/OFF Valve
sensor
DAC
Digital Signal
Analogue
signal
ADC
Check values from sensor to stored values in memory
Digital Signal

8. Why using microprocessor for monitoring and control?
It is safer
processor will respond faster when non-standard condition occurs
It does not get tired
It will not miss key data
Computers work 24/7

9. Why using microprocessor for monitoring and control?
Computers are more accurate
It can take accurate readings especially when taking readings at short time intervals
e.g taking readings at intervals of 5 seconds for a period of 24 hours
Data can be automatically displayed and analysed
No need to enter data manually thus reducing the risk of typo errors

10. Example of Control system- An Automated Greenhouse
A light sensor – detect light the plants are getting
A temperature sensor -how cold/hot greenhouse is
A moisture sensor - how wet/dry the soil is
Actuator
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

11. The process for this system would be...
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