Jamrom2
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Power issue on PI3

Sat Jan 28, 2017 8:12 pm

Hi quick question on power for my Pi3...

I originally had a PI2 and decided to upgrade to the PI3.

Power to the PI2 was supplied by this 5v 5a - 25w unit from Mean Well... it worked flawlessly.
http://www.alliedelec.com/mean-well-usa ... /70387190/

After upgrading to the Pi3, I was getting a lot of lightening bolts telling me I needed more power. So I bought this 7.5v 2a 15w unit from the same company. Lowered the amps... upped the volts.
https://www.alliedelec.com/mean-well-us ... /70349496/

unfortunately, it does not power-up the Pi3... which I don't understand why. The unit is good as I get the rated 7.5v at the pin-outs... but nothing happens.

Did I buy the wrong unit thinking I was doing the right thing?

Thanks in advance.

JR

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FTrevorGowen
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Re: Power issue on PI3

Sat Jan 28, 2017 8:22 pm

Jamrom2 wrote: ...
After upgrading to the Pi3, I was getting a lot of lightening bolts telling me I needed more power. So I bought this 7.5v 2a 15w unit from the same company. Lowered the amps... upped the volts.
https://www.alliedelec.com/mean-well-us ... /70349496/
...
JR
I hope you didn't literally "up the volts" - that's not the right thing to do. If you're lucky the P3's overvoltage protection circuitry will have tripped the polyfuse before damage was done and the Pi may recover in a day or two. The "lightning bolt" is (one of) the low-voltage warnings (the other is an off or flickering red PoWeR led) which means that the voltage at the Pi is falling below ~4.6V because either the PSU cannot provide 5V at the current being drawn and/or said current is leading to to much voltage drop in the connecting cable. If that's of the USB to uUSB type then either it's too long and/or its conductors are too thin.
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B+, P3B, B+, and a A+) but Buster on the P4B's & P400. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

Jamrom2
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Re: Power issue on PI3

Sat Jan 28, 2017 9:00 pm

Yes, I literally did just that. No damage to the Pi, but my card is smoked... I'm rebuilding it now.

The Pi boots and reads my Retropie boot splash graphic, then stops. But other than that, it's still ok.

My setup is the 25w PS, into a modified micro USB power cord. I added a two pin clip to attach it to the 25w PS. From there it's all micro usb. It worked great on the Pi2.

So how can I solve this constant lightening bolt issue with the new Pi3? Do I need a larger power supply?

Thanks,

JR

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davidcoton
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Re: Power issue on PI3

Sat Jan 28, 2017 9:03 pm

Pis are designed to run on almost exactly 5V. Anything over 5.25V is out of spec and may cause damage. As Trev said, if you hacked a connected to the microUSB you may be lucky and the polyfuse may have tripped before damage was done -- but if you connected via the GPIO header, you bypassed the protection and it's Bye Bye Pi.

Try again tomorrow with the older supply. The most likely problem with that is the cable from supply to Pi. You need something as short as possible with thick conductors. Do not try again with 7.5V!
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Jamrom2
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Re: Power issue on PI3

Sat Jan 28, 2017 9:24 pm

Lol... message received loud and clear.

Yes, my power is running through the protection circuit. So the Pi was safe.
Thanks for the help....

I'll return that 7.5v PS and stick with what was working. I didn't realize that I would do so much damage.

JR

sparkyhall
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Re: Power issue on PI3

Sat Jan 28, 2017 10:42 pm

The meanwell 5V 5A PSU you linked to in your first post has a small voltage adjuster next to the two pin output connector (labeled SVR1 in datasheet), according to the datasheet this allows you to adjust the output voltage between 4.75V and 5.5V. Ideally you want to set the output to 5.1V with a multimeter, if you do not have a multimeter, with power off, try turning SVR1 1/8th of turn clockwise and see if the lightning bolts go away. Note: The datasheet does not specify which way increases the output voltage so you may need to turn SVR1 anti-clockwise.

alphanumeric
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Re: Power issue on PI3

Sat Jan 28, 2017 10:46 pm

5V @ 5A should be plenty for most setups if the power cord is beefy enough. A long cord with thin wires can be an issue. The thin wires will have enough resistance to create a voltage drop across them. If the voltage drop is excessive you'll get the lightning bolt flashing telling you the voltage at the power jack is too low. The Pi and what's connected to it will only draw what current it needs. My Pi 3B running KODI with just a TV and keyboard connected runs just fine on a 2.5 A power pack. If I had issues I would up the current not the voltage. My bread board setup has a 5V 10 A power pack for example. Its a bit overkill but it runs nice and cool and I don't have any worries of ever overloading it.

alphanumeric
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Re: Power issue on PI3

Sat Jan 28, 2017 10:49 pm

Yeah, I've seen a few Pi power packs that are 5.1V or even 5.2V. Even under heavy load that gets you your 5V at the power jack on a Pi 3B.

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Re: Power issue on PI3

Sun Jan 29, 2017 12:24 am

Jamrom2 wrote:Lol... message received loud and clear.

Yes, my power is running through the protection circuit. So the Pi was safe.
Thanks for the help....

I'll return that 7.5v PS and stick with what was working. I didn't realize that I would do so much damage.
Could be worse...get the voltage high enough and the polyfuse can't stop it. People have been known to apply a 12v supply to Pis and then come to the Forums wondering why their Pi doesn't work any more.

W. H. Heydt
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Re: Power issue on PI3

Sun Jan 29, 2017 12:27 am

alphanumeric wrote:5V @ 5A should be plenty for most setups if the power cord is beefy enough.
5A is more than a Pi will use, no matter what is attached to it. The protection circuitry will limit the current draw to about 2.5A on a Pi3 (and less on earlier models). The only Pi that could, even in theory, draw 5A is the Pi Zero, and then only because the Pi Zero doesn't have any protection circuits, though 5A would probably blow board traces.

alphanumeric
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Re: Power issue on PI3

Sun Jan 29, 2017 10:43 am

W. H. Heydt wrote:
alphanumeric wrote:5V @ 5A should be plenty for most setups if the power cord is beefy enough.
5A is more than a Pi will use, no matter what is attached to it. The protection circuitry will limit the current draw to about 2.5A on a Pi3 (and less on earlier models). The only Pi that could, even in theory, draw 5A is the Pi Zero, and then only because the Pi Zero doesn't have any protection circuits, though 5A would probably blow board traces.
Yes, on a 3B its ~ 400ma for the Pi itself and a max of 1.2A combined for the 4 USB ports. 2.5A is more than enough for a stock setup. If you have extra bits connected like a power splitter cable and a Pi 7 inch screen, you may want the extra Amps over a 2.5A power pack though.

On my breadboard rig I made my own custom USB cables. Data comes from my Pi but power to the USB devices comes from my power pack, bypassing my Pi. No current restrictions this way. No lightning bolt or tripping the poly fuse either.

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