In this article, we will explain step-by-step how an electronic board controls the fan of an air conditioning system using a relay. This system leverages switching and regulation technology to ensure efficient operation.
1. Power Input to the System
The air conditioning system operates with 220 V alternating current (AC), which is directly supplied to the control circuit.
2. Initial Voltage Reduction
The electronic board receives the 220 V AC and directs it to a transformer, reducing the voltage to approximately 16 V AC.
3. Conversion to Direct Current
The reduced voltage passes through a rectifier bridge and capacitors, converting the alternating current into direct current (DC).
4. Voltage Regulation
The DC voltage is processed through two voltage regulators:
- 7812 Regulator: Reduces and stabilizes the voltage to 12 V DC.
- 7805 Regulator: Converts the 12 V to 5 V DC, providing the power needed for sensitive electronic components.
5. User Power-On Signal
When the user activates the system:
- The electronic board sends a signal to the main controller.
- The controller responds by sending a 5 V signal to the ULN 2003 integrated circuit.
6. Activation of the ULN 2003 Circuit
- The ULN 2003 receives the input signal at pin 3 and generates an output signal at pin 14.
- This output signal at pin 14 acts as a ground signal, enabling the current flow in the next component of the circuit.
7. Relay Operation
The relay has an internal coil requiring 12 V to operate:
- The ground signal from the ULN 2003 allows current to flow through the relay’s coil.
- This generates a magnetic field within the relay.
8. Activation of the Relay’s Internal Switch
The magnetic field closes the relay’s internal switch, allowing the 220 V AC to flow toward the fan.
9. Powering the Fan
Once the relay is activated, the fan receives the 220 V AC, enabling its operation.
