Raspberry Pi Forums

Hi,
I'm using an M3-ATX molex connector to power the Pi but I'm getting the underpowered icon in the top right corner. Since the M3-ATX, which is a 125W PSU, is powering the Pi only (and an iDrive controller) I really can't understand why the icon is appearing.
I read online that you can set the Pi to draw more current from the micro USB but I can't find any info is that something you can really do?
Thank you in advance

The pi will only draw what current it needs, you cant make it draw more current.

The low volt icon is present because you supply voltage is be low the required 5V , have you actually measured what you power supply is actually outputting using a meter ?

how are you using the PC psu as a power supply is you just have it powered by connecting the on cable to ground, if so then it wont work correctly as it has to have load on the 5V rail of at least 5 watts.

there are examples on the web on how to set up a pc psu as a bench power supply.

Or you could just ignore the "undervolt icon". I get it from time to time on various systems; it never seems to mean anything or hurt anything.

n67 wrote: ↑

Sat Apr 14, 2018 11:20 am

Or you could just ignore the "undervolt icon". I get it from time to time on various systems; it never seems to mean anything or hurt anything.

The problem is that if the pc psu does not have the minimum load on it the voltage stabilisation may not work, which could result in not only a low volt condition which he has now, but also a high volt condition which could damage the pi.

So ignoring the problem may not be the best option.

For my work setup (from a 100W desktop variable voltage/current PSU)
I have it connected via thick 4mm bananaplug wire all the way to the two outer uUSB connectors.
I still need to bump the voltage up to 5.15V for the lightning bolt to go away on Pi2/Pi3.
Try bumping your voltage up a bit.

(It reads perfectly fine at the Pi, just doesn't like to be at or a bit below 5V for some reason).

You get use to it.

And91 wrote: ↑

Sat Apr 14, 2018 7:32 am

Hi,
I'm using an M3-ATX molex connector to power the Pi but I'm getting the underpowered icon in the top right corner. Since the M3-ATX, which is a 125W PSU, is powering the Pi only (and an iDrive controller) I really can't understand why the icon is appearing.
I read online that you can set the Pi to draw more current from the micro USB but I can't find any info is that something you can really do?
Thank you in advance

What cable are you using between the PSU and Pi. To thin and/or too long a cable will mean voltage is dropped along the length of the cable so even if the PSU is giving out 5V the Pi might be seeing under 4.85v (I think that's around the threshold for the warning).

Whilst there might not be visible effects from a low voltage warning on the Pi it's possible there's silent corruption happening on SD card which would cause issues at some point in the future.

mfa298 wrote: ↑

Sat Apr 14, 2018 6:39 pm

To thin and/or too long a cable will mean voltage is dropped along the length of the cable so even if the PSU is giving out 5V the Pi might be seeing under 4.85v (I think that's around the threshold for the warning).

IIRC, the threshold is 4.65V (but I might be a bit out). The permitted range (USB spec) is 5.0V +/- 0.25V, so anything over 4.75V should not produce a warning. The Pi itself will work with significant undervoltage, but there might be problems for USB or HDMI. Everything (?) else including the SDCard runs at 3V3 or below, there should be no problems until the 3V3 regulator drops out (normally well below 4V). There are differences between different Pi models, and YMMV for specific Pis.