How to Make Temperature Switch using C945 Transistor

Introduction

Temperature switch is an electronic device that can be used to control various systems based on the surrounding temperature. These switches use transistors, such as the C945 transistor, along with other components like the 10K thermistor, 1N4007 diode, and 3V zener diode. This temperature switch using C945 can maintain temperature of any small covered area. We have tried to make this circuit as easy as it could be. In this article, we will discuss in detail how to make temperature switch using C945 transistor and other components like 10K thermistor,, 1N4007 diode and 3V zener diode etc.

Introduction of Major Components:

C945 Transistor

The C945 transistor is a widely used NPN transistor that can be employed in various electronic circuits. It is a low-power amplifier and switching transistor that offers high current gain and low voltage output. The C945 transistor can handle a maximum voltage of 50V, making it suitable for many applications.

One of the key features of the C945 transistor is its ability to amplify weak signals, making it useful for audio and radio frequency applications. It has three terminals – the emitter, base, and collector. The base-emitter junction of the transistor controls the current flow through the collector-emitter junction, making it an excellent choice for switching applications.

10K Thermistor

A thermistor is a type of resistor that exhibits a change in resistance based on temperature. The 10K thermistor is a thermistor with a resistance of 10,000 ohms at 25 degrees Celsius. As the temperature changes, the resistance of the thermistor either increases or decreases, depending on the type of thermistor.

In the temperature switch circuit, the 10K thermistor is used to sense the surrounding temperature. When the temperature exceeds a certain threshold, the resistance of the thermistor changes, triggering the operation of the switch.

1N4007 Diode

The 1N4007 diode is a widely used rectifier diode that is capable of handling high voltages and currents. It is commonly used in power supply circuits to convert alternating current (AC) to direct current (DC). The 1N4007 diode is a silicon diode and offers a maximum reverse voltage of 1000V.

The primary function of the 1N4007 diode in the temperature switch circuit is to protect the other components from reverse voltage. It allows current flow in one direction, preventing any damage to the circuit due to reversed polarity.




3V Zener Diode

Zener diodes are special types of diodes that operate in the reverse-biased region and maintain a constant voltage across the diode terminals. The 3V zener diode, as the name suggests, has a breakdown voltage of 3V. When the voltage across the zener diode exceeds 3V, it starts conducting, keeping the voltage across the diode constant.

In the temperature switch circuit, the 3V zener diode is used to provide a stable reference voltage. This reference voltage is used as a comparison with the voltage across the 10K thermistor to determine if the temperature has exceeded the desired limit.

Temperature Switch using Transistor
Temperature Switch using C945 Transistor

Circuit Diagram of Temperature Switch using C945

This project can be designed using a few basic components. The circuit diagram of this project is shown below.

Temperature Switch using Transistor Circuit Diagram
Temperature Switch using C945 Circuit Diagram




Temperature Switch using Transistor Schematic
Temperature Switch using C945 Schematic

More Circuit Layouts






Components List of Temperature Switch using C945

Following is the list of all components used in this project:

  • 1X 10K thermistor
  • 2X C945 transistors
  • 1X 1N4007 diode
  • 1X 3V zener diode
  • 1X 100uf 50V capacitors (electrolytic)
  • 1X 12V relay
  • 1X 2pin terminal block
  • 1X 3pin terminal block
  • 2X 10K resistors (1/4 watt)
  • 2X 1K resistors (1/4 watt)
  • 1X 2.2K resistors (1/4 watt)
  • 1X 10K variable resistors
  • 1X LED
  • vero board
  • jumper wires




Connections of Temperature Switch using C945

Now that we have familiarized ourselves with the key components, let’s discuss how to make the temperature switch using these components.

Step-1: First insert a 2-pin terminal block and connect positive and negative of the 12v power supply. Next insert a 3-pin terminal block and a 12v relay together. Connect pin-1 of terminal block to Normally Closed pin, Center pin to Common pin of relay and pin-3 to Normally Open pin of the relay. Also connect coil pin-2 of the relay to positive supply. Next connect Anode of 1n4007 diode to coil pin-1 while the cathode of the diode to positive supply.

Step-2: Insert first C945 transistor and connect its pin-1 to ground, pin-2 to coil pin-1 of the relay. Take one LED and connect its cathode to pin-2 of C945 transistor. Also take a 1k resister and connect it to the anode of the LED while the other side wil go the positive supply. Now take a 10 resister and connect it between pin-3 of C945 transistor and ground. Also connect a 100uf capacitor’s positive to pin-3 of C945 transistor while the negative will connected to the ground.

Step-3: Next insert a second C945 transistor and connect its pin-1 to ground. Now take another 10k resister and connect it to pin-2 of second C945 transistor and the other side to pin-3 of the first C945 transistor. Connect a 2.2k resister from positive supply to pin-2 of second C945 transistor.

Step-4: Insert a 5k Trimpot and connect its pin-1 to ground and center pin to pin-3 of the second transistor. Also insert a 10 Thermister and connect its one pin-1 to pin-3 of 5k Trimpot. Now insert a 3v Zener diode and connect its cathode to pin-2 to 10k thermistor and anode to ground. Also connect a 1k resister from pin-2 of 10 thermistor to positive supply.

To protect the transistor and other components from reverse voltage, connect the 1N4007 diode in reverse bias across the power supply terminals. This diode will prevent any damage to the circuit due to polarity reversal.




Conclusion of Temperature Switch using C945

Temperature switches are versatile devices that can be used in various applications to control systems based on the surrounding temperature. By using components like the C945 transistor, 10K thermistor, 1N4007 diode, and 3V zener diode, one can easily construct a temperature switch circuit.

The C945 transistor provides the amplification necessary to detect temperature changes, while the 10K thermistor senses the temperature. The 1N4007 diode protects the circuit from reverse voltage, and the 3V zener diode provides a stable reference voltage.

When the temperature exceeds the desired threshold, the resistance of the thermistor changes, triggering the operation of the temperature switch. This switch can then be used to control various systems, such as fans, heaters, and other appliances, based on the surrounding temperature.

In conclusion, making a temperature switch using C945 transistor, 10K thermistor, 1N4007 diode, and 3V zener diode is a simple yet effective way to control systems based on temperature. Whether it is for industrial or domestic applications, temperature switches play a vital role.

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