wojclerry
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Will more current damage my Pi?

Fri Jul 28, 2017 3:13 pm

Hello,
I am using a Pi 2B and it won't boot when I power it while some periphals (wireless keyboard/mouse, usb sound card, ethernet) are plugged in.
Could this be an issue caused by insufficient power supply? I was using 1A.
What if I upgraded to 3A? Is this a good idea? Cause, I can't find anything between the range of 2.1A and 3A in the market.

fruitoftheloom
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Re: Will more current damage my Pi?

Fri Jul 28, 2017 3:21 pm

wojclerry wrote:
Fri Jul 28, 2017 3:13 pm
Hello,
I am using a Pi 2B and it won't boot when I power it while some periphals (wireless keyboard/mouse, usb sound card, ethernet) are plugged in.
Could this be an issue caused by insufficient power supply? I was using 1A.
What if I upgraded to 3A? Is this a good idea? Cause, I can't find anything between the range of 2.1A and 3A in the market.
https://www.raspberrypi.org/help/faqs/#topPower

https://thepihut.com/products/official- ... wer-supply

There are many vendors who sell the Official 5.1V 2.5A Power Supply and is highly recommended..
Thinking outside the box is better than burying your head in the sand...

W. H. Heydt
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Re: Will more current damage my Pi?

Fri Jul 28, 2017 4:12 pm

A Pi2B will never draw more than about 1.8A (it's limited by its own current limiting polyfuse), so a 2A supply is sufficient...provided it will deliver 5v at full current draw. You don't say where you are, but here: http://www.mcmelectronics.com/product/28-19335 is an eample of a PSU suitable for a Pi2B. Or, of course, you can--as already noted--use the officially vetted RPF PSU.

In any case, don't discard your 1A unit. It can be used to power an A+, B+, Pi0, or Pi0W. None of those boards need as much as 1A.

pcmanbob
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Re: Will more current damage my Pi?

Fri Jul 28, 2017 4:36 pm

wojclerry wrote:
Fri Jul 28, 2017 3:13 pm
Hello,
I am using a Pi 2B and it won't boot when I power it while some periphals (wireless keyboard/mouse, usb sound card, ethernet) are plugged in.
Could this be an issue caused by insufficient power supply? I was using 1A.
What if I upgraded to 3A? Is this a good idea? Cause, I can't find anything between the range of 2.1A and 3A in the market.
In answer to your question your pi will only draw what current it needs so if you use a 5V 3A power supply it will not be any different to using a 5V 2A power supply.
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hippy
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Re: Will more current damage my Pi?

Sat Jul 29, 2017 10:00 am

The current capacity rating of a power supply is what it can deliver, not what a Pi uses. As long as the supply can deliver more than the Pi needs it will be fine.

It is like fitting a larger fuel tank to a vehicle. It won't run the engine any faster, it won't damage the engine.

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Ronaldlees
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Re: Will more current damage my Pi?

Sat Jul 29, 2017 2:31 pm

Maybe the OP has gone already, but I noticed he didn't say which brand supply he is using. I have noticed that some cheaper supplies get quite hot if operated very close to the advertised maximum current level. In fact, one such unit could not be used at much over 50 percent of the advertised current, without excessive heat.

So, buying an oversized supply can have benefit, even if the expected current draw is not close to the maximum rating of the supply. It'll run cooler, maybe last longer ...
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W. H. Heydt
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Re: Will more current damage my Pi?

Sun Jul 30, 2017 12:05 am

Ronaldlees wrote:
Sat Jul 29, 2017 2:31 pm
Maybe the OP has gone already, but I noticed he didn't say which brand supply he is using. I have noticed that some cheaper supplies get quite hot if operated very close to the advertised maximum current level. In fact, one such unit could not be used at much over 50 percent of the advertised current, without excessive heat.

So, buying an oversized supply can have benefit, even if the expected current draw is not close to the maximum rating of the supply. It'll run cooler, maybe last longer ...
That is very typical of the reasoning for installing a higher rated than needed PSU in a PC. Lower load, runs cooler, lasts longer.

The bigger issue with "wall wart" PSUs for Pis is that, when you approach the rated current, the voltage drops off with lower quality units and all sorts of problems start happening. So using a PSU rated above--within some linits--of what a Pi actually needs does sort of "double duty".

boyoh
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Re: Will more current damage my Pi?

Sun Jul 30, 2017 1:43 pm

Using high current power supply's can have it's problems If used on low current circuits
This can be lack of over current protection, so some kind of over current is advisable
On low current circuits. The choice is between a blown fuse or a burnt circuit board.
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Moe
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Re: Will more current damage my Pi?

Sun Jul 30, 2017 10:38 pm

All USB-compliant supplies will supply 4.75-5.25V at the rated current - at the output. The cheaper they are, the closer they will be to the rated current. They will get hot, but they are designed to get hot.

In my experience, the problems start when you plug a cheap USB cable into a wall-wart phone charger and see the voltage at the far end drop to about 4V :o
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W. H. Heydt
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Re: Will more current damage my Pi?

Sun Jul 30, 2017 10:57 pm

Moe wrote:
Sun Jul 30, 2017 10:38 pm
All USB-compliant supplies will supply 4.75-5.25V at the rated current - at the output. The cheaper they are, the closer they will be to the rated current. They will get hot, but they are designed to get hot.

In my experience, the problems start when you plug a cheap USB cable into a wall-wart phone charger and see the voltage at the far end drop to about 4V :o
The "phone charger" units are built assuming that they are going to be charging a 3.7v battery and so long as they voltage stays enough above that, everything is okay. The Pi really needs over 4.7v and will complain if it doesn't get it. Plus some USB peripherals are fairly picky aobut get at least 4.75v. As a result, cheap "phone chargers" and Pis don't always get along well together.

Moe
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Re: Will more current damage my Pi?

Wed Aug 02, 2017 8:18 pm

The "phone charger" units are built assuming that they are going to be charging a 3.7v battery and so long as they voltage stays enough above that, everything is okay. The Pi really needs over 4.7v and will complain if it doesn't get it. Plus some USB peripherals are fairly picky aobut get at least 4.75v. As a result, cheap "phone chargers" and Pis don't always get along well together.
It would not be loegal to sell those (in Europe at least). If it's rated at 5V 1A it needs to supply 1A @ >4.75.
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drgeoff
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Re: Will more current damage my Pi?

Wed Aug 02, 2017 8:29 pm

Moe wrote:
Wed Aug 02, 2017 8:18 pm
The "phone charger" units are built assuming that they are going to be charging a 3.7v battery and so long as they voltage stays enough above that, everything is okay. The Pi really needs over 4.7v and will complain if it doesn't get it. Plus some USB peripherals are fairly picky aobut get at least 4.75v. As a result, cheap "phone chargers" and Pis don't always get along well together.
It would not be loegal to sell those (in Europe at least). If it's rated at 5V 1A it needs to supply 1A @ >4.75.
That something is illegal does not prevent it happening in Europe. And I doubt that Europe is an exception.
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Burngate
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Re: Will more current damage my Pi?

Thu Aug 03, 2017 9:24 am

Moe wrote:
Wed Aug 02, 2017 8:18 pm
It would not be legal to sell those (in Europe at least). If it's rated at 5V 1A it needs to supply 1A @ >4.75.
I'm not sure that's true.
If it says it adheres to the USB spec, then it should "supply 1A @ >4.75", but if it's sold as a phone charger, then all it has to do is charge a phone.
The USB plug on the end of the cable is only there for the convenience of the user, and doesn't imply any adherence to the USB spec.
After all, it doesn't carry data at even the lowest USB data rate (there being no data wires) but no-one's been sued over that, yet.

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bensimmo
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Re: Will more current damage my Pi?

Thu Aug 03, 2017 10:03 am

Also if the cable is built in, then the spec will be for the end of the cable.

If it's not built in, then the spec will be for the start of the cable. I.e. when no cable is used. Hence the cable become a problem.

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