In this tutorial, we are making a project on a Temperature control circuit using 555 IC. There are a lot of different circuits for temperature control but this circuit is different from them because it is using 555 timer IC. The 555 timer IC is the most commonly used IC in all Electronic projects. It is used to oscillate or provide short or long time delays and it can also be used as a flip-flop element in a circuit. This IC has various applications and it is inexpensive therefore it is widely used.
This circuit will control any AC or DC device at the desired temperature. The 555 IC is working as a bistable multivibrator. A bistable multivibrator provides an output pulse when it receives a trigger pulse at the input. In our circuit, the input is received by the thermistor when it senses temperature.
Hardware Components
The following components are required to make Temperature Control Circuit
| S.no | Component | Value | Quantity |
|---|---|---|---|
| 1. | DC supply | 12V | 1 |
| 2. | Thermistor | – | 1 |
| 3. | IC | NE555 Timer | 1 |
| 4. | Variable Resistor | 5K | 1 |
| 5. | Ceramic Capacitor | 10nF | 1 |
| 6. | LED | – | 1 |
| 7. | Relay | 12V | 1 |
| 8. | Diode | 1N4007 | 1 |
| 9. | Resistor | 470Ω | 1 |
NE555 IC Pinout
For a detailed description of pinout, dimension features, and specifications download the datasheet of 555 Timer
Temperature Control Circuit
Working Explanation
A thermistor is used to detect the presence of heat. Initially, the circuit remains turned off but when the thermistor receives heat its resistance decreased and it lets the current flow through it. The 555 timer IC receives an output signal and provides an output that will activate the LED and the relay. LED is used for visual indication of the relay activating.
Two variable resistors of 5K ohms are used to adjust the circuit to activate the relay at the desired temperature. A 1N4007 diode is used across the relay to limit the back EMF of the coil in the relay. The operating voltage of this circuit is 12V but it can also work on a 6V battery or power supply. Make sure to use a relay of the same voltage as the input supply
Applications and uses
- Fans
- Heat Alarms
- Overheating indicators
