PC Fans

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* Noctua's [https://noctua.at/pub/media/wysiwyg/Noctua_PWM_specifications_white_paper.pdf PWM Specification White Paper] (unknown date, but it references 1.3 <i>ibid</i>)

Almost all available fans are either 5V, 12V, or 24V, with 12V dominating personal computers:

* there is no readily-available 24V source from an [[ATX]] power supply, but you'll see 24V in e.g. [[3D printers]]

* there is no readily available 24V source from an [[ATX]] power supply, but you'll see 24V in e.g. [[3D printers]]

* 5V fans are seen in conjunction with MCUs such as [[Raspberry Pi]]

Fans operating at higher voltages will require less current for the same work. Two-pin fans offer neither feedback nor dedicated PWM control. Three-pin fans typically offer a tachometer signal on the third wire. Four-pin fans add a PWM control on the fourth wire. PWM is a <b>5V logical control</b> that does not modify supplied power. In the absence of PWM support, some control can be effected by varying voltage (voltage ought be held constant for a PWM fan), but since a minimum voltage is necessary to avoid stalling, only the higher-speed range is available. "Low-frequency PWM" applies PWM to the power wire itself, but suffers from audible commutation noise, and must apply pulse stretching to the tachometer.

PC Fans: Difference between revisions

Dank (talk | contribs)

@@ Line 6: / Line 6: @@
 * Noctua's [https://noctua.at/pub/media/wysiwyg/Noctua_PWM_specifications_white_paper.pdf PWM Specification White Paper] (unknown date, but it references 1.3 <i>ibid</i>)
 Almost all available fans are either 5V, 12V, or 24V, with 12V dominating personal computers:
-* there is no readily-available 24V source from an [[ATX]] power supply, but you'll see 24V in e.g. [[3D printers]]
+* there is no readily available 24V source from an [[ATX]] power supply, but you'll see 24V in e.g. [[3D printers]]
 * 5V fans are seen in conjunction with MCUs such as [[Raspberry Pi]]
 Fans operating at higher voltages will require less current for the same work. Two-pin fans offer neither feedback nor dedicated PWM control. Three-pin fans typically offer a tachometer signal on the third wire. Four-pin fans add a PWM control on the fourth wire. PWM is a <b>5V logical control</b> that does not modify supplied power. In the absence of PWM support, some control can be effected by varying voltage (voltage ought be held constant for a PWM fan), but since a minimum voltage is necessary to avoid stalling, only the higher-speed range is available. "Low-frequency PWM" applies PWM to the power wire itself, but suffers from audible commutation noise, and must apply pulse stretching to the tachometer.