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Pi4b J2 Run Global_En as power

Posted: Wed Jul 10, 2019 3:40 pm
by Mettauk
Wondering what these are for and is it OK to run a very small fan from here (25x25x7mm 5v 0.2a) on either the 3.3v or the 4.75v side as tested? I want to keep the 40pin GPIO header clear for other stuff and don't really want to solder underneath
J2.jpg
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Re: Pi4b J2 Run Global_En as power

Posted: Wed Jul 10, 2019 4:28 pm
by dp11
These pins aren't suitable for running a fan.

Re: Pi4b J2 Run Global_En as power

Posted: Wed Jul 10, 2019 5:02 pm
by trejan
RUN is for resetting the SoC. GLOBAL_EN is for signalling the PMIC to leave the low power shutdown state. Neither should be used for powering a fan.

Re: Pi4b J2 Run Global_En as power

Posted: Wed Jul 10, 2019 5:18 pm
by IrishBrewer
I was kind of hoping they would put a fan header on the board for the same reasons stated by the OP. Seems like a simple thing to do that would keep the 40-pin header "clean". With the performance increases making it viable to use the current incarnation as a lite desktop device, active cooling (combined with passive) becomes more important.

Re: Pi4b J2 Run Global_En as power

Posted: Wed Jul 10, 2019 7:49 pm
by Imperf3kt
In case it needs to be noted, the third hole in the center is ground.

Re: Pi4b J2 Run Global_En as power

Posted: Wed Jul 10, 2019 8:14 pm
by chipace
The GLOBAL_EN pin has 100k Ohms to 5V, you are not going to get any current from that connection (and if you did you would reset the part). RUN is an input to the SOC (you could damage the SOC). The GND connection between those pins would probably be fine.
You probably don't need a fan, unless you are mining bitcoin.

Re: Pi4b J2 Run Global_En as power

Posted: Sat Aug 03, 2019 2:23 pm
by SeyfertR
Thank you all so much for the information. :D I have a case from a bundler that has a fan and plugging it into the GPIO where they instruct to sort of defeats the purpose of GPIO bridging. I might have burned the thing out one day into ownership.

I guess I will solder V+ to the bottom of the board and recommend that they fire their case engineer. :lol:

Now I need to find the thread for partitioning a 64GB microSD card into 2 ea 32GB partitions, so that I can have a OS and Data drive, as only *nix can do.

Take care, God bless and be safe.

Rich