# Arduino Fan Controller

This project is an Arduino-based fan controller that allows you to adjust the speed of a 4-pin PWM fan using a push button. It also measures and displays the fan's RPM via the serial monitor.

## Features
- PWM control of a 4-pin fan
- RPM measurement using the fan's tachometer output
- Speed adjustment in 10% increments via a push button
- Serial output of current speed and RPM

## Hardware Requirements
- Arduino board (Uno, Nano, etc.)
- 4-pin PWM fan
- NPN transistor (for PWM control)
- Push button
- Resistors (as needed for button and transistor)
- Wires and breadboard

## Pin Configuration
- **pwmPin (9):** PWM output to transistor base
- **tachPin (2):** Tachometer input from fan
- **buttonPin (7):** Push button input

## How It Works
- The fan speed is controlled by PWM signal on pin 9.
- The push button on pin 7 increases the speed by 10% each press, cycling from 0% to 100%.
- The tachometer signal from the fan is read on pin 2 using an interrupt to count pulses.
- Every second, the RPM is calculated and printed to the serial monitor along with the current speed percentage.

## Usage
1. Connect the hardware as described above.
2. Upload the `ArduinoFanController.ino` sketch to your Arduino.
3. Open the serial monitor at 9600 baud to view speed and RPM.
4. Press the button to increase fan speed in steps.

## Schematic

Below is a simple schematic for connecting the components (updated for a 5V fan, 1kΩ resistor, and two capacitors in parallel to the fan):


```
				 +5V (Fan Power)
						 |
					 [Fan]
						 |
				 +---+---+
				 |   |   |
				 |   |   +-- PWM (Pin 9, Arduino) via 1kΩ resistor
				 |   +------ Tach (Pin 2, Arduino)
				 |
				GND
				 |
			[C1] 100uF Electrolytic
			[C2] 104pF Ceramic
			(C1 and C2 in parallel to the fan)

	 [Button]
		 |
	 Pin 7 (Arduino)
		 |
		GND

	 [NPN Transistor]
	 Collector: Fan GND
	 Base: PWM (Pin 9, Arduino) via 1kΩ resistor
	 Emitter: Arduino GND
```

**Notes:**
- The fan is powered by 5V.
- A 1kΩ resistor is used between Arduino pin 9 (PWM) and the transistor base.
- Two capacitors (100uF electrolytic and 104pF ceramic) are connected in parallel to the fan for noise filtering and stability.
- The tachometer wire goes directly to Arduino pin 2.
- The button is connected between pin 7 and ground, with a pull-up resistor enabled in code.

## Notes
- The RPM calculation assumes the fan generates 2 pulses per revolution.
- You can modify the code to set the speed via serial input (see commented section in the code).

## License
This project is open source and free to use for personal and educational purposes.