37 lines
1.1 KiB
Text
37 lines
1.1 KiB
Text
#include <TimerOne.h>
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// This example creates a PWM signal with 25 kHz carrier.
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//
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// Arduino's analogWrite() gives you PWM output, but no control over the
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// carrier frequency. The default frequency is low, typically 490 or
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// 3920 Hz. Sometimes you may need a faster carrier frequency.
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//
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// The specification for 4-wire PWM fans recommends a 25 kHz frequency
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// and allows 21 to 28 kHz. The default from analogWrite() might work
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// with some fans, but to follow the specification we need 25 kHz.
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//
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// http://www.formfactors.org/developer/specs/REV1_2_Public.pdf
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//
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// Connect the PWM pin to the fan's control wire (usually blue). The
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// board's ground must be connected to the fan's ground, and the fan
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// needs +12 volt power from the computer or a separate power supply.
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const int fanPin = 4;
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void setup(void)
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{
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Timer1.initialize(40); // 40 us = 25 kHz
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Serial.begin(9600);
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}
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void loop(void)
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{
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// slowly increase the PWM fan speed
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//
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for (float dutyCycle = 30.0; dutyCycle < 100.0; dutyCycle++) {
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Serial.print("PWM Fan, Duty Cycle = ");
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Serial.println(dutyCycle);
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Timer1.pwm(fanPin, (dutyCycle / 100) * 1023);
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delay(500);
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}
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}
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