Monitoring and Control

Designed by V.Paupiah PGCE 2011-2012 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 Designed by V.Paupiah PGCE 2011-2012

Designed by V.Paupiah PGCE 2011-2012 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 Designed by V.Paupiah PGCE 2011-2012

Designed by V.Paupiah PGCE 2011-2012 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) Designed by V.Paupiah PGCE 2011-2012

Designed by V.Paupiah PGCE 2011-2012 sensor ADC Analogue signal Digital Signal Designed by V.Paupiah PGCE 2011-2012

Designed by V.Paupiah PGCE 2011-2012 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 Designed by V.Paupiah PGCE 2011-2012

sensor DAC ADC Analogue signal Turn ON/OFF Valve Digital Signal Check values from sensor to stored values in memory Digital Signal Designed by V.Paupiah PGCE 2011-2012

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 Designed by V.Paupiah PGCE 2011-2012

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 Designed by V.Paupiah PGCE 2011-2012

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 Designed by V.Paupiah PGCE 2011-2012

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 Designed by V.Paupiah PGCE 2011-2012