In this tutorial, we are making an automatic temperature-controlled fan using a 555 timer IC. This circuit is quite interesting and simple, it can automatically control the speed of the fan according to the temperature. if you frequently make an electronic circuit or are familiar with them then you must be familiar with the 555 timer IC, it is commonly used in hundreds of circuits for different purposes like time delay, oscillators, trigger signals, etc. It is versatile, easy to use, inexpensive, and readily available anywhere.
Any type or size of 12V DC fans marked 1 to 1.5-ampere ratings can be used with this circuit to control their speed. This circuit can be used at any place where a supply of 12 volts is available. A very interesting and simple project of a highly sensitive static electricity detector circuit can also be used as an ion detector, electric field detector, etc.
Hardware Components
The following components are required to make Temperature Controlled Fan Circuit
| S.no | Component | Value | Quantity |
|---|---|---|---|
| 1. | DC Supply | 12V | |
| 2. | Thermistor | 20K NTC | 1 |
| 3. | Resistor | 20K, 1K | 1, 1 |
| 4. | DC Fan | 12V | 1 |
| 5. | IC | NE555 timer | 1 |
| 6. | Diode | 1N4007 | 1 |
| 7. | Transistor | BD139 | 1 |
| 8. | Ceramic Capacitor | 0.1µF, 0.01µF | 1, 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Temperature Controlled Fan Circuit
Working Explanation
The operating voltage of this circuit is 12 volts. A 10K NTC thermistor is used to sense the temperature or heat. When heat is received by the transistor it sends a signal to the 555 timer IC and it is activated. A BD139 transistor is used to drive the 12V fan. To save this transistor from the back EMF of the fan coil we have used a diode across the fan.
The speed of the fan depends on the value of the resistor R1, and the temperature at which it activates depends on the value of the NTC thermistor. So, you can change their values and experiment to make the speed of the fan as desired at a suitable temperature.
Applications and Uses
- Heat sensor Fans
- Temperature controlled fans
- Temperature-controlled Lamp, etc.
