4 Pin PWM Fan Speed Controller help required

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skinnybattery
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4 Pin PWM Fan Speed Controller help required

Post by skinnybattery » Sat Apr 01, 2017 3:12 pm

Hello everybody.

I'm quite new to this so please forgive my lack of knowledge.

Here is the fan. It is a NF-A14 PWM 140mm.

http://noctua.at/en/nf-a14-pwm/specification

I would like to have temperature based fan speed control using the WiPy 2.0.

The ESP32 datasheet has provisions for DC Motor PWM control and I have an led going up and down in brightness using PWM for testing purposes.

Would it be just a simple case of hooking up the fan and writing in the code or do you think I would need an IC fan speed controller also.

This is for a BSc computer science project.

Your help would be greatly appreciated.

Kind regards.

Marc.

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dhylands
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Re: 4 Pin PWM Fan Speed Controller help required

Post by dhylands » Sat Apr 01, 2017 6:53 pm

My understanding is that most of these fans like a 25 kHz PWM signal. You should be able to generate that directly from the WiPy.
This document has more details about the 4-wire fans used in most computers:
http://www.formfactors.org/developer/sp ... m_spec.pdf

Newer fans should accept a 3.3v PWM signal, otherwise you may need to drive it through some type of voltage translation (typically just a MOSFET).

The extra wire is a tachmoeter signal that can be used to detect if the fan is actually spinning or not. The tachometer signal is open drain so it should work with a 3,3v pullup, but again, you may need voltage translation here as well.

skinnybattery
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Re: 4 Pin PWM Fan Speed Controller help required

Post by skinnybattery » Sun Apr 02, 2017 2:30 pm

Thanks for you response.

The only reason I'm using the fan is because I have one available.

Could you recommend an easier solution where minimal external circuitry is required.

I'd like to design with high reliability in mind.

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dhylands
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Re: 4 Pin PWM Fan Speed Controller help required

Post by dhylands » Sun Apr 02, 2017 7:11 pm

If its a newer fan, then probably no external circuitry is required. I think you need a pullup resistor to use the tach (pullup to 3.3v). If the fan is moving and you can see pulses on the tach line with a 3.3v pullup then you're good.

I'd just try feeding a 25 kHz 3.3v signal on the PWM line and see if it wrks or not.

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