caldimerda
Posts: 67
Joined: Tue Oct 09, 2012 9:41 am

Is there a Pi 4 Undervoltage warning?

Sat Jul 13, 2019 8:12 am

Hi
I've not seen an undervoltage lightning bolt with my pi 4. I've tried to provoke one by using a low power output supply and it runs happily with no sign of a problem.
I ask because I do have a variety of issues with the new pi and on the older devices a lot of problems came down to low voltage. But I have an idea that we aren't being warned by the device if it sees a low voltage condition.
Thanks

DJCrispyRice
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Joined: Sat Jul 13, 2019 12:18 pm

Re: Is there a Pi 4 Undervoltage warning?

Sat Jul 13, 2019 2:15 pm

I have 2 power supplies (one 2A and one 3A) and the first one shows the lightning signal when I use it. I can't even boot anything else than Noobs.

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mahjongg
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Re: Is there a Pi 4 Undervoltage warning?

Sat Jul 13, 2019 3:07 pm

The valid (best) option to test this is by making sure it receives good power, by trying if the official (RPI4) supply solves the mysterious crashes.
if not it's not power related.

caldimerda
Posts: 67
Joined: Tue Oct 09, 2012 9:41 am

Re: Is there a Pi 4 Undervoltage warning?

Wed Jul 17, 2019 2:06 pm

mahjongg wrote:
Sat Jul 13, 2019 3:07 pm
The valid (best) option to test this is by making sure it receives good power, by trying if the official (RPI4) supply solves the mysterious crashes.
if not it's not power related.
Hi Mahjjong
I'm not quite sure I folow your logic. I wasn't asking if an undervoltage issue is causing my issues. I am pretty sure it's not but I've had problems years ago that were so I try not to assume. I just wondered why I'd not seen the liughtning symbol when I was trying power supplies that didn't claim to output 3A. It looks like DJCrispyRice has seen the lightning bolt but I've still not seen a post from anyone else saying they have on a Pi 4. I'll try a bit harder with some of my more obviously incapable supplies and cables.
Thanks, David

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jbeale
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Re: Is there a Pi 4 Undervoltage warning?

Wed Jul 17, 2019 2:25 pm

FWIW, the most the Pi 4 draws at idle without external USB devices, even with the original stock firmware and 4k enabled is 3720 mW according to https://www.martinrowan.co.uk/2019/07/r ... e-at-idle/

and at 5V that is only 0.744 amps, which is a long way away from 3 amps. As I recall the very most it will draw at full load (but without external power draw from devices like USB HDD) is about 1.8 A

The reason the official supply is rated for 3.1 A is to allow up to 1.2 A power draw from the USB ports while the Pi is running flat out.

drgeoff
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Re: Is there a Pi 4 Undervoltage warning?

Wed Jul 17, 2019 3:18 pm

Yes the RPi4B has an undervoltage detector and it triggers the same lightning bolt seen with previous models.

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