Obviously you might have seen so many temperature controller and indicator applications using different microcontrollers, micro-processors or other controlling devices. But this is the actual application of temperature controller that controls speed of DC fan as temperature varies. It is not a simple ON-OFF type controller that switches fan ON / OFF when temperature increases / decreases certain limit. But it is a type of controller that continuously varies speed of DC fan as temperature increases / decreases. That is a demo of actual industrial application.
In industry fan may be AC or DC (most probably AC) or it may be cooler. As the temperature increases the speed of fan also increases linearly to cool it down. And as temperature decreases the speed also decreases. For any constant temperature the speed also remains constant.
So here I present a demo of same kind of application. As the temperature increases from 25 oC to 55 oC the speed of DC fan increases from min to max. obviously the industrial temperature range will be in terms of 100 oC to 100 oC or even more but here for demo I have design it for very low range. At the end of article I have suggested some ideas some modifications with which the project can be used for actual industrial application.
Temperature Controlled Fan Block Diagram: -
The figure shows major building blocks of the system as temperature sensor, ADC (Analog to Digital Convertor), micro-controller (AT89C52), DC driver and 5-LED bar graph display. Let us see the function of each block in brief.
Temperature sensor: - it’s a transducer. It converts temperature into equivalent electrical signal. Its output voltage increases linearly with increase in temperature. So by measuring the output voltage we may observe increase or decrease in temperature.
ADC: - because the output of sensor is an analog form, it must be converted into equivalent digital form before it is given to micro-controller. So, 8-bit ADC converts analog signal from sensor into 8-bit digital signal that is given to micro-controller.
Micro-controller: - it performs following tasks
· Controls ADC and reads digital value at periodic interval
· Generates PWM and controls speed of DC fan through DC driver
· Indicates current speed on LED bar graph display.
LED bar graph: - its 5-step bar graph that displays min speed as one LED ON and max speed as all five LEDs ON
DC Driver: - the direct micro-controller output is not able to drive DC motor. So the DC driver will take input PWM signal from micro-controller and generates enough current to drive DC motor through this PWM.