Temperature control fan circuit diagram. If the temperature drops below 40 deg celsius as per the code. When the temperature increases the base current of q1 bc 547 increases which in turn decreases the collector voltage of the same transistor. The circuit switches on a fan if it senses a temperature above the set level. Step down transformer reduces 230v ac into 12v ac.
The fan automatically turns off when the temperature returns to normal. Download project code circuit 2 temperature controlled dc fan using atmega8 circuit diagram. 2 shows circuit diagram of the digital temperature controller. Digital temperature controller circuit and working.
The circuit uses an ntc negative temperature coefficient thermister to sense heat. A capacitor 1000uf is used to avoid the unwanted ac ripples. If the temperature exceeds more than 50 deg celsius as per the code the microcontroller will turn on the relay to start the fan. Here is a simple circuit based on two transistors that can be used to control the speed of a 12 v dc fan depending on the temperaturea thermistor r1 is used to sense the temperature.
Ic lm324 has four comparators each having an inverting and non inverting terminal. This circuit is ideal to control the cooling fan of heat generated electronic gadgets like power amplifiers. Thermistor is temperature sensitive resistor whose resistance changes according to the temperature. The key component of this temperature controlled fan circuit is thermistor which has been used to detect the rise in temperature.
Below is the circuit diagram for temperature controlled dc fan using thermistor as temperature sensor. The circuit is built around microcontroller pic16f877a ic1 precision thermocouple amplifier ad8495 ic2 k type thermocouple connected at con3 162 lcd lcd1 single changeover relay rl1 and a few common components. It is then converted into dc by a bridge rectifier circuit. Here temperature sensor should be interfaced correctly to the microcontroller in order to get correct reading.
There are two types of thermistor ntc negative temperature co efficient and ptc positive temperature co efficient we are using. Temperature controlled dc fan block diagram temperature sensor lm35 is interfaced with the 8051 microcontrollers analog pin because temperature sensor changes temperature into voltage.