martin5504
Posts: 4
Joined: Fri Aug 17, 2018 8:22 am

5V FAN to 3.3V pin

Thu Sep 13, 2018 4:35 pm

Hi guys,

I have this fan for my Pi https://www.aliexpress.com/item/New-Ras ... 69888.html

But is litle more louder then I can endure, can I connect this fan to 3.3v pin? Is this healthy for RPI? Could this help with silence of fan?

Thanks for help.

pcmanbob
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Location: Mansfield UK

Re: 5V FAN to 3.3V pin

Thu Sep 13, 2018 5:08 pm

I would advise against connecting the fan to the 3.3v pin on the pi gpio.
You could end up damaging your pi if the fan should put any noise or reverse voltages on to the pin, which it might do on pi shutdown.

If you want to reduce its speed permanently just add a resistor in series with the fan when connecting it to the pi.

Or use a transistor and a gpio pin to apply pwm speed control to the fan for variable speed control.
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martin5504
Posts: 4
Joined: Fri Aug 17, 2018 8:22 am

Re: 5V FAN to 3.3V pin

Thu Sep 13, 2018 6:31 pm

Okay cool thanks,

so only with transistor I can control speed too right?

https://hackernoon.com/how-to-control-a ... 13b6e7f92c

So this tutorial is for transistor and a gpio pin to apply pwm speed control ?

Brandon92
Posts: 473
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Location: Netherlands

Re: 5V FAN to 3.3V pin

Thu Sep 13, 2018 6:52 pm

No really, you need also add a base resistor for the transistor. And add a fly back diode across your fan, for protection.

pcmanbob
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Location: Mansfield UK

Re: 5V FAN to 3.3V pin

Thu Sep 13, 2018 6:58 pm

As Brandon92 has already said you need more components than just a transistor.

Image

this is the sort of circuit you need to control a 5v fan using a gpio pin.
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martin5504
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Joined: Fri Aug 17, 2018 8:22 am

Re: 5V FAN to 3.3V pin

Thu Sep 13, 2018 7:02 pm

Understood, but for only shutting and turning on the fan is enough only the transistor right?

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: 5V FAN to 3.3V pin

Thu Sep 13, 2018 7:06 pm

No, that is not correct. You need this ^ schematic for turning on and off your fan.

pcmanbob
Posts: 4355
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: 5V FAN to 3.3V pin

Thu Sep 13, 2018 7:09 pm

martin5504 wrote:
Thu Sep 13, 2018 7:02 pm
Understood, but for only shutting and turning on the fan is enough only the transistor right?
no to control the fan or even to just turn it on or off you need the extra components.

if you just want the fan to run at a constant speed you could just use this circuit, the fan will be on as long as the pi is powered.

Image

the value of R ? will have to be found by experimentation, but 22Ω might be a good starting value going lower for higher speed or higher for a lower speed.
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