Fitting a fan without using GPIO?

[IKE007]

Sorry if this is a dumb question - I have briefly searched the forum and can't find any references.
Anyway, I'm fitting my Pi4 into a case that comes with a standard fan (5V). I do not want to power it via the GPIO as I need to have all 40 pins connected through the ribbon cable to an extension board into a breadboard, for other project activities. So far, everything I read says to use a couple of the GPIO pins, but I can't, as described above. Can I use any of those 4 pins at J14 PoE, behind the Ethernet port? Any other suggestions.
Thanks

[duckredbeard]

Hack an old phone charger if the fan only needs 5V. Fan always on. Or have the Pi control a relay that enables the fan under certain conditions.

[ElEscalador]

It's a petty pet peeve of mine that we can't get a couple of pins for a fan without interrupting access to the entire header. The choices are to splice into your ribbon cable, find a place on the board to solder to, or power via USB - you can get little US breakouts with screw terminals.

[rpiMike]

Google: GPIO splitter

Might be an option.

[sirozha]

Spend $25 on an Argon One case. It has a fan and also provides access to all 40 GPIO pins under a magnetic cover. There are two versions of the case: for Raspberry Pi 3 and 4. The case also has a power button and uses an easily installed script to be able to completely power down the Raspberry Pi by regular OS tools or by pressing and holding the power button for 3 seconds. It also allows you to force-shut the Raspberry Pi by holding the power button for over 5 seconds, to adjust the temperature when the fan kicks in, etc. You can also restart the Raspberry Pi by regular OS tools when the script is installed. No more fiddling with plugging/unplugging the power supply.

I’ve been using this case with the Raspberry Pi 4B for over a month now. It’s simply perfect.

[hippy]

Can I use any of those 4 pins at J14 PoE, behind the Ethernet port?

No.

[W. H. Heydt]

It's a petty pet peeve of mine that we can't get a couple of pins for a fan without interrupting access to the entire header. The choices are to splice into your ribbon cable, find a place on the board to solder to, or power via USB - you can get little US breakouts with screw terminals.

That's why I suggested that--given the existing thermal problems--future Pis get a fan header. Not going to happen on the Pi4B (if only because of the very tight trace routing), but it *might* happen on a future board.

[IKE007]

Hack an old phone charger if the fan only needs 5V. Fan always on. Or have the Pi control a relay that enables the fan under certain conditions.

A good idea but, in my mind, that goes against the "keeping it simple" concept. Thanks for the idea though.
Cheers

[IKE007]

It's a petty pet peeve of mine that we can't get a couple of pins for a fan without interrupting access to the entire header. The choices are to splice into your ribbon cable, find a place on the board to solder to, or power via USB - you can get little US breakouts with screw terminals.

I agree, I'm disappointed that we have to think up options though. In my opinion, especially with the Pi4, the designers have missed a trick here. Thanks for your suggestions though.
Cheers.

[IKE007]

Google: GPIO splitter

Might be an option.

Thanks for the suggestion. I had planned to put everything in the case, which has the fan built in to the top/lid, but there's no room for the splitter inside the case. Just seems a shame that this was not thought of for the Pi4.
Cheers.

[IKE007]

Spend $25 on an Argon One case. It has a fan and also provides access to all 40 GPIO pins under a magnetic cover. There are two versions of the case: for Raspberry Pi 3 and 4. The case also has a power button and uses an easily installed script to be able to completely power down the Raspberry Pi by regular OS tools or by pressing and holding the power button for 3 seconds. It also allows you to force-shut the Raspberry Pi by holding the power button for over 5 seconds, to adjust the temperature when the fan kicks in, etc. You can also restart the Raspberry Pi by regular OS tools when the script is installed. No more fiddling with plugging/unplugging the power supply.

I’ve been using this case with the Raspberry Pi 4B for over a month now. It’s simply perfect.

Thanks for the suggestion. My case (with the fan built-in) has the 40 pin cable permanently plugged in and fed into the breadboard, via a Pi Extension board. My power supply is switchable too. Just seems that the designers missed an option for a simple feed to a fan?
Cheers

[IKE007]

Can I use any of those 4 pins at J14 PoE, behind the Ethernet port?

No.

Thanks for your reply. A simple answer. However, it now poses another question in my mind: Why not? Are these input or output jumpers? I'm tempted to put a tester on them - unless there is an official schematic for the Pi4?
Cheers.

[PeterO]

You could get a Pimoroni fan-shim and use your case fan instead of the built in one.
https://shop.pimoroni.com/products/fan-shim
PeterO

[IKE007]

Can I use any of those 4 pins at J14 PoE, behind the Ethernet port?

No.

Thanks for your reply. A simple answer. However, it now poses another question in my mind: Why not? Are these input or output jumpers? I'm tempted to put a tester on them - unless there is an official schematic for the Pi4?
Cheers.

Aha! Just found a schematic. TR0/1/2/3 TAPs for PoE. Ah well, every day's a school day.

[scotty101]

Can I use any of those 4 pins at J14 PoE, behind the Ethernet port?

No.

Thanks for your reply. A simple answer. However, it now poses another question in my mind: Why not? Are these input or output jumpers? I'm tempted to put a tester on them - unless there is an official schematic for the Pi4?
Cheers.

The 4 pins are connected to the ethernet port and are designed to draw power from the ethernet cable that is then passed to the PoE hat before being stepped down to 5V which then supplies the Pi via the GPIO ports. There will be no voltage on those pins unless you are connected via ethernet cable to a PoE switch.
They are shown on the schematic as TR<1-4>_TAP

[Imperf3kt]

Why not do the obvious?
connect your ribbon cable to your breadboard, and power your fan... from your breadboard.

[LTolledo]

this is how I did it on my RPi3B+

RPi3B+FanPower.jpg (195.21 KiB) Viewed 589 times

been doing like this on all RPi Model B boards that I have
like the RPi4B-4G below

RPi4B-4G_Armorcase.jpg (195.05 KiB) Viewed 589 times

[LTolledo]

my breadboard pi with fan power

BreadBoardPi_view2.jpg (195.86 KiB) Viewed 582 times

[boyoh]

You could fit the Fan in the Pi box , and having it temperature controlled just using the
3.3v rail and 5volt for the fan , Using a NTC Thermistor switching a transistor to
switch the fan on and off , The thermistor is Temperature controlled resistor
If you do use a Thermistor use a preset in series for setting

Regards BoyOh

[neilgl]

Good layout.
No one needs a fan?

[boyoh]

Pi Board.jpg (60.13 KiB) Viewed 485 times

You could use this board for building your projects on , I fitted 4 slotted Opto Isolators for voltage leveling
and projects control .All built on Vero Board .Good project for learner

Regards BoyOh