sasagr
Posts: 1
Joined: Sun Oct 13, 2019 5:01 pm

Raspberry pi 4 and fan

Sun Oct 13, 2019 5:09 pm

Hi.
I m at my third pi device, after the pi and the pi 3 I got the pi 4 with 4GB of Ram.
I just bought this also.
https://www.amazon.co.uk/GeeekPi-Raspbe ... =8-2-fkmr2

I was reading that it is not a good idea, actually bad, to connect it to the 3V gpio pin. Maybe the 5V but not the 3V.
I was wondering if the pi4 being more powerful and getting higher power can handle this fan directly connected to the gpio without being too worried about SoC damages.
Any feedback would be much appreciated.

Thanks

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Imperf3kt
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Location: Australia

Re: Raspberry pi 4 and fan

Sun Oct 13, 2019 6:49 pm

The fear about using a 3v pin on the GPIO header is that it's only supposed to supply a small amount of current and a fan may draw more than it can supply.


From anecdotal evidence I've read on the forums here, it seems to work just fine, so it's up to you if you proceed.
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davidcoton
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Re: Raspberry pi 4 and fan

Sun Oct 13, 2019 9:12 pm

The fan should not be connected directly to a GPIO. It is likely to draw too much current, and may produce back EMF when switched off. Either of these will damage the Pi.

The Amazon listing does not give a specification for the fan supply (neither voltage nor current). You might get away with connecting the fan to the uncontrolled 3V3 supply on the GPIO header, but I personally would not try even that. The 5V supply should be OK. I would be inclined to try a thermally controlled drive from a GPIO via a transistor to the 5V supply, but without a spec for the fan it is impossible to give proper advice.
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W. H. Heydt
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Location: Vallejo, CA (US)

Re: Raspberry pi 4 and fan

Mon Oct 14, 2019 1:24 am

davidcoton wrote:
Sun Oct 13, 2019 9:12 pm
The fan should not be connected directly to a GPIO. It is likely to draw too much current, and may produce back EMF when switched off. Either of these will damage the Pi.

The Amazon listing does not give a specification for the fan supply (neither voltage nor current). You might get away with connecting the fan to the uncontrolled 3V3 supply on the GPIO header, but I personally would not try even that. The 5V supply should be OK. I would be inclined to try a thermally controlled drive from a GPIO via a transistor to the 5V supply, but without a spec for the fan it is impossible to give proper advice.
Once again, I have to point out that pretty everything that mounts on a Pi grabs the first 6 pins, which includes the only 2 5v pins. The problem in this area that I'm looking at is connecting an RTC and a fan. So the fan is going to have to run of a 3.3v pin.

LTolledo
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Re: Raspberry pi 4 and fan

Mon Oct 14, 2019 1:44 am

not a solution for the weak-willed and/or shaky-hand types.....
RPi3B+FanPower.jpg
RPi3B+FanPower.jpg (195.21 KiB) Viewed 652 times
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

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Imperf3kt
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Location: Australia

Re: Raspberry pi 4 and fan

Mon Oct 14, 2019 5:42 am

LTolledo wrote:
Mon Oct 14, 2019 1:44 am
not a solution for the weak-willed and/or shaky-hand types.....
RPi3B+FanPower.jpg
I would consider adding some form of strain relief to that connection. Your soldering is very neat, but it'd probably ruin your day if you accidentally lifted one of those pads because the cable snagged on something.
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boyoh
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Re: Raspberry pi 4 and fan

Mon Oct 14, 2019 11:14 pm

If you use the Pi as it should be used, you don’t
Need extra heat sinks or fans, Just use the Pi
Low current to switch transistors and
Opto isolators as buffer stages Such as voltage
Levelling and current amplifying from a separate
Power supply to run your project

Regards BoyOh
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

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Imperf3kt
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Location: Australia

Re: Raspberry pi 4 and fan

Mon Oct 14, 2019 11:43 pm

boyoh wrote:
Mon Oct 14, 2019 11:14 pm
If you use the Pi as it should be used, you don’t
Need extra heat sinks or fans, Just use the Pi
Low current to switch transistors and
Opto isolators as buffer stages Such as voltage
Levelling and current amplifying from a separate
Power supply to run your project

Regards BoyOh
We need 1.5GHz and 4GB of RAM for that?

Maybe the first Pi has those as it's intended use, but the Pi4 has clearly been designed to be used for much more than that.

The Pi's 'intended use' now appears to be dual display advertising machines.
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52:4C:52:42:41

boyoh
Posts: 1342
Joined: Fri Nov 23, 2012 3:30 pm
Location: Selby. North Yorkshire .UK

Re: Raspberry pi 4 and fan

Tue Oct 15, 2019 11:19 am

Imperf3kt wrote:
Mon Oct 14, 2019 11:43 pm
boyoh wrote:
Mon Oct 14, 2019 11:14 pm
If you use the Pi as it should be used, you don’t
Need extra heat sinks or fans, Just use the Pi
Low current to switch transistors and
Opto isolators as buffer stages Such as voltage
Levelling and current amplifying from a separate
Power supply to run your project

Regards BoyOh
We need 1.5GHz and 4GB of RAM for that?

Maybe the first Pi has those as it's intended use, but the Pi4 has clearly been designed to be used for much more than that.

The Pi's 'intended use' now appears to be dual display advertising machines.
Is it getting to the point that the Raspberry Pi
Will lose it’s Credit Card Size, The latest Pis
Are having to many components crammed on
To the PCB. This raises the point of higher temperature due to cramped components
Also making them run faster can cause higher
Temperature rise, Fast changing signals tend
To draw more current at their peak change

Regards boyoh
BoyOh ( Selby, North Yorkshire.UK)
Some Times Right Some Times Wrong

alphanumeric
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Joined: Tue Jan 19, 2016 2:17 pm
Location: Sydney, Nova Scotia, Canada

Re: Raspberry pi 4 and fan

Tue Oct 15, 2019 11:51 am

W. H. Heydt wrote:
Mon Oct 14, 2019 1:24 am
davidcoton wrote:
Sun Oct 13, 2019 9:12 pm
The fan should not be connected directly to a GPIO. It is likely to draw too much current, and may produce back EMF when switched off. Either of these will damage the Pi.

The Amazon listing does not give a specification for the fan supply (neither voltage nor current). You might get away with connecting the fan to the uncontrolled 3V3 supply on the GPIO header, but I personally would not try even that. The 5V supply should be OK. I would be inclined to try a thermally controlled drive from a GPIO via a transistor to the 5V supply, but without a spec for the fan it is impossible to give proper advice.
Once again, I have to point out that pretty everything that mounts on a Pi grabs the first 6 pins, which includes the only 2 5v pins. The problem in this area that I'm looking at is connecting an RTC and a fan. So the fan is going to have to run of a 3.3v pin.
You can connect multiple devices to the +5V pins. I use a Proto Hat. I solder my RTC board right to it then add headers for anything else I want to connect. If you use a stacking header you can plug a hat in on top of the proto hat.
https://www.adafruit.com/product/2310

EDIT: One of the items being a Fan complicates things though.

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