shadowbyte
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5v, 3amp ok?

Sat Jul 09, 2016 2:45 am

I happened across a bunch of 5v 3amp and 5v 2.5amp power supplies that only needed a small adapter to make them work for the pi. I've been testing one on an old cell phone without issue.

Any problem with using 3amp supplies with the raspberry pi?

Thanks

W. H. Heydt
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 3:58 am

Any device will only draw the current it needs, so a higher current supply works. The only potential issue would be something on the board caused it draw more current than it's own power regulation or board traces can handle. That way, the "magic smoke" escapes and you'll be in the market for a new Pi...plus there will be the risk of fire that could do a lot of damage to things around the failing unit.

All of that said...a 3A supply should not be a problem as it's not very much over spec.

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MarkHaysHarris777
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 6:23 am

To add to Heydt's comment above, the exception these days to the rule are the new Samsung fast changers that will not only provide the right current, BUT, they will also bump up to 9v !! ... and that will blow your PI. Be very careful about PSU that claim to be 'fast' chargers because they will 9v your PI and destroy it !

marcus
marcus
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piglet
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 7:53 am

Don't fast chargers use a data negotiation to determine whether they can bump the voltage? The Pi won't respond, so will get 5v

mosespi
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 8:01 am

MarkHaysHarris777 wrote:To add to Heydt's comment above, the exception these days to the rule are the new Samsung fast changers that will not only provide the right current, BUT, they will also bump up to 9v !! ... and that will blow your PI. Be very careful about PSU that claim to be 'fast' chargers because they will 9v your PI and destroy it !

marcus
This is just disinformation. You will not blow up your Pi with any Samsung quick charger that I am aware of. There is a specific handshake that occurs before these types of 'fast' chargers ramp up to a higher voltage. Imagine the backlash that Samsung (or Qualcomm, which has the other fast charger standard) would get if they put a higher voltage on a standard micro USB connector by default, frying phones and Pis left and right.

Unless you think your quick charger was from some shoddy factory with fake markings.. I wouldn't worry.

Regards,
-Moses
Power problems? MoPower UPS for the Pi
http://www.allspectrum.com/mopower/

shadowbyte
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 3:59 pm

A little more information..

These are 5v/2.5a and 5v/3.0a power supplies that were pulled from old DSL modems. They have a PC-style plug on one side and a wire with a 2.1mm barrel connector on the other. I purchased a few .99c adapters to adapt from the barrel to the proper plug and they seem to fit very nicely. I figure if it will charge a cell phone, then the polarity is correct. I rescued a bag of these, so I'm thinking I have all the Raspberry Pi supplies I'll ever want for .99c each. (Got some Pi Christmas gifts I'm working on already.)

They give the appearance of being a product that was well made for the application they were intended.

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FTrevorGowen
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 4:39 pm

shadowbyte wrote:A little more information..
These are 5v/2.5a and 5v/3.0a power supplies that were pulled from old DSL modems. They have a PC-style plug on one side and a wire with a 2.1mm barrel connector on the other. I purchased a few .99c adapters to adapt from the barrel to the proper plug and they seem to fit very nicely. I figure if it will charge a cell phone, then the polarity is correct. I rescued a bag of these, so I'm thinking I have all the Raspberry Pi supplies I'll ever want for .99c each. (Got some Pi Christmas gifts I'm working on already.)
They give the appearance of being a product that was well made for the application they were intended.
FWIW, you could perform some "load curve" measurements in a similar fashion to what I've done since the first Pi's release:
https://www.cpmspectrepi.uk/raspberry_p ... t.2FMethod
https://www.cpmspectrepi.uk/raspberry_p ... dPSUs.html **
which may add to the "confidence factor".
Trev.
** Some of these were not "uUSB power supplies" and used barrel connectors.
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. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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HawaiianPi
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 4:47 pm

MarkHaysHarris777 wrote:To add to Heydt's comment above, the exception these days to the rule are the new Samsung fast changers that will not only provide the right current, BUT, they will also bump up to 9v !! ... and that will blow your PI. Be very careful about PSU that claim to be 'fast' chargers because they will 9v your PI and destroy it !

marcus
mosespi wrote:This is just disinformation. You will not blow up your Pi with any Samsung quick charger that I am aware of. There is a specific handshake that occurs before these types of 'fast' chargers ramp up to a higher voltage. Imagine the backlash that Samsung (or Qualcomm, which has the other fast charger standard) would get if they put a higher voltage on a standard micro USB connector by default, frying phones and Pis left and right.

Unless you think your quick charger was from some shoddy factory with fake markings.. I wouldn't worry.

Regards,
-Moses
Moses is correct. Qualcomm Quick Charge (and Samsung QC, which is basically the same thing) chargers will only output 5V unless they can verify that the device is QC compatible with a data handshake. They are not going to fry a Pi, because it will not pass the handshake verification.

In general, only devices with a Qualcomm Snapdragon processor or a Qualcomm QC chip on board will be able to use QC. The Pi has neither. My Zero is running off one of my QC 2.0 chargers as I type this, and according to my DVM it's receiving 4.99V.
My mind is like a browser. 27 tabs are open, 9 aren't responding,
lots of pop-ups...and where is that annoying music coming from?

pivoron
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Re: 5v, 3amp ok?

Sat Jul 09, 2016 5:08 pm

You got a lot of good information above, so here's a bit more.

If you are interested in the Rpi, (and who would not be?), your enjoyment and education will become more and more advanced. I would recommend you start out by obtaining a VOM, (Volt Ohm Meter), which can be bought for a really minimal amount of money and it is a great way to start your work with computers/electronics.

I say this because those power supplies can sometimes be devilish with regard to the polarity of the round power plug. MOST of the time the outer sleeve is negative, BUT not ALWAYS! Yep, some irascible designers like to mess you up and use the opposite polarity. Now you can be sure to check the polarity before you place the plug anywhere near your Pi.

You can select AC on your VOM and get an idea of any AC ripple present on some cheap supplies that could render your Pi erratic. So, you are off to a good start by obtaining a VOM for your electronics career.

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