4-Wired Fan Control (PWM)

I simply want to control a 4-wired fan (or maybe several) with an Arduino board. There is some information out there. Many projects that use a temp sensor, but never the most simple thing: control the speed of the fan.I found useful code in this thead: <a href="https://forum.arduino.cc/index.php?topic=155089.msg1175321#msg1175321">https://forum.arduino.cc/index.php?topic=155089.msg1175321#msg1175321</a><pre ><code >int pwmPin = 3; // digital PWM pin 9 int pwmVal = 1; // The PWM Value unsigned long time; unsigned int rpm; String stringRPM; void setup() { // generate 25kHz PWM pulse rate on Pin 3 pinMode(pwmPin, OUTPUT); // OCR2B sets duty cycle // Set up Fast PWM on Pin 3 TCCR2A = 0x23; // COM2B1, WGM21, WGM20 // Set prescaler TCCR2B = 0x0A; // WGM21, Prescaler = /8 // Set TOP and initialize duty cycle to zero(0) OCR2A = 79; // TOP DO NOT CHANGE, SETS PWM PULSE RATE OCR2B = 0; // duty cycle for Pin 3 (0-79) generates 1 500nS pulse even when 0 : digitalWrite(2, HIGH); // Starts reading Serial.begin(9600); } void loop() { unsigned int x; // ramp up fan speed by increasing duty cycle every 200mS, takes 16 seconds //for(x = 0; x &lt; 80; x++) { // OCR2B = x; // set duty cycle // getRPMS(); // Serial.println(x); // delay(200); //} while (Serial.available() == 0); int val = Serial.parseInt(); if (val &gt; 0 &amp;&amp; val &lt; 80) { OCR2B = val; } } char getRPMS() { time = pulseIn(2, HIGH); rpm = (1000000 * 60) / (time * 4); stringRPM = String(rpm); if (stringRPM.length() &lt; 5) { Serial.println(rpm, DEC); } } </code></pre>Wiring:<figure><img src=https://projects.arduinocontent.cc/52d305eb-8dfa-4065-97c0-6efd2fb9650d.jpg /><figcaption> </figcaption></figure>

4-Wired Fan Control (PWM)

Control a PWM fan with Arduino.