With using timer interrupt , Lm35 (Temprature sensor) ,LCD 2*16 and DC fan , An interrupt is executed when the temperature reaches 50 degrees or higher. The ISR sends a signal that operates the fan and keeps working until the temperature is back below 50 degrees and display the elipsaed time
#SW Using proteues8.13 and fritzing in simulation , and micro c pro for pic in coding
#Hardware LCD 2*16 CRYSTAL4MHZ Resistors and Variable Resistor Realy module or Design it using 2N2222 NPN transistor,4N35 Optocoupler and Relay LM35 temprature sensor lm339 quad differential comparator Pic16f877a