pedro_javierf
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Small Fan using GPIO.

Mon Nov 30, 2015 5:20 pm

I'm not sure if this post goes here, anyways.

I have bought a small 2 pin cooler fan that im goin to use with the raspberry pi (B+)
Image
I've found this picture in google. The size is basically the same, and fits fine on top of my raspberry box.

So, in the fan sticker it says 12V... As far as I'm concerned GPIO can't manage that amount of voltage, so, is it any risk in damaging them? I mean, if I plug the fan, Will the raspberry try to run it at 12V? For my it is fine to run at 3V or 5V if it don't hurt my GPIO/or the entire motherboard.

Thanks for your help.
My best regards,

pedro_javierf

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DougieLawson
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:23 pm

Pull it off and toss it away before you destroy your RPi. There is ZERO value in adding a fan. Your RPi won't run hot.
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rpdom
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:25 pm

Best not to use it. Although the GPIO can't and won't try to supply 12V, the electrical noise from the motor could cause problems.

Why do you want to use a fan anyway?

pedro_javierf
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:29 pm

Yes, I know...

But I'm going to be running it for long times at max overclock range so I found it usefull because my raspberry (unfortunately) becames hot.


Thanks anyway.

pedro_javierf
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:31 pm

Well, at the moment my fan says 12V, so i was wrong by buying it because I need a 5 or less V fan.

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DougieLawson
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:34 pm

My eight Raspberries run 24/365. Normal is 45°C. They've never got anywhere near hot which is 85°C. But I do live on a small, green, wet island that doesn't get much above 35°C, even in the height of summer.

NOT ONE OF THEM HAS OR NEEDS A FAN.

Just forget it, it won't do any useful except generate an annoying noise.
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rpdom
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:37 pm

pedro_javierf wrote:Well, at the moment my fan says 12V, so i was wrong by buying it because I need a 5 or less V fan.
A 12V fan powered from 5V will just run slower. It should be plenty enough to cool a Pi (even though the Pi doesn't need any cooling. Chips do get a bit hot. They are designed to allow for that.)

pedro_javierf
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:39 pm

rpdom wrote:
pedro_javierf wrote:Well, at the moment my fan says 12V, so i was wrong by buying it because I need a 5 or less V fan.
A 12V fan powered from 5V will just run slower. It should be plenty enough to cool a Pi (even though the Pi doesn't need any cooling. Chips do get a bit hot. They are designed to allow for that.)
That is what I wanted to know. I was terrified because I thought that if I pluged a higher voltage it will try to (forcefully) power it with 12 V, instead of powering it with the maximun it can (5V). So, taking apart the noise and a lower speed, there aren't any risk, are they?

Thanks in advance,
pedro_javierf

EDIT: Sorry I forget, shall I turn HIGH the GPIO pins, shall not I? And which pins? Mine is B+ with 40 pins. Thanks!

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joan
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:44 pm

pedro_javierf wrote: ...
EDIT: Sorry I forget, shall I turn HIGH the GPIO pins, shall not I? And which pins? Mine is B+ with 40 pins. Thanks!
You must NOT use a GPIO. Use the ground and 5V pins on the expansion header.

The fan will introduce a little interference and may make your overclocked system less reliable.

pedro_javierf
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 5:51 pm

joan wrote:
pedro_javierf wrote: ...
EDIT: Sorry I forget, shall I turn HIGH the GPIO pins, shall not I? And which pins? Mine is B+ with 40 pins. Thanks!
You must NOT use a GPIO. Use the ground and 5V pins on the expansion header.

The fan will introduce a little interference and may make your overclocked system less reliable.
Image
4 pin to red wire and 6 pin to black wire should do the job, don't they?

Thanks for your fast reply!

PD: Thanks for your help, my last question: I've read that motors like this one has some kind of "called back EMF" that could damage pins, does this atack 5v&GND pins or only the others non power supply pins?

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joan
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Re: Small Fan using GPIO.

Mon Nov 30, 2015 6:00 pm

pedro_javierf wrote: ...
PD: Thanks for your help, my last question: I've read that motors like this one has some kind of "called back EMF" that could damage pins, does this atack 5v&GND pins or only the others non power supply pins?
Yes, 4 and 6 will be fine.

Back EMF can kill a GPIO. The power rail pins like 4 and 6 should not be affected.

pedro_javierf
Posts: 11
Joined: Fri Nov 06, 2015 4:47 pm

Re: Small Fan using GPIO.

Mon Nov 30, 2015 6:22 pm

So this experiment...

Has had succes! Fan has worked fine when pluged to pins 4 and 6 (5V & GND), obviously, it's not really fast, but enough for a long period of time.

You could use it when you are going to use the raspberry for a long time
But you should not use it in short periods of time because it makes the temperature to increase a bit (or it seemed to me) due to the use of 5V extra voltage from GPIO.

I'm not sure if I have explained nice, I hope yes.

My best regards!
pedro_javierf

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