Casimov
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Is a power supply of 5.25V/2.4A safe to use with RasPi 3?

Wed Feb 01, 2017 3:27 pm

Bought my first Raspberry Pi 3. Unfortunately, the only power supply left was a 5.25V/2.4A power supply. Im only using my Raspberry Pi for emulators. Is this power supply overkill? Is it safe to use?

This is the power supply I bought: http://www.mcmelectronics.com/product/P ... -/28-19336

"Highly regulated switching power supply. Extremely high efficiency (up to 90%). 4' cord and Micro USB connector with strain relief."
No-load voltage regulation within 3% of rated output. Load regulation: +/- 3%.

Is this safe to use, or is it too much? I know that the recommended amount is 5V for Raspberry Pi 3 Model B, which is the Raspberry Pi model I have. Im worried that I might damage mine by using this power supply. Im not using any peripherals, aside from a simple USB controller that will be plugged into the Raspberry Pi. Will the Raspberry Pi overheat? Get damaged? Thanks in advance.

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bensimmo
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Wed Feb 01, 2017 5:17 pm

It'll be grand, if you hadn't noticed it's a recommendation choice (frequently bought together)

hippy
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Wed Feb 01, 2017 6:43 pm

Casimov wrote:5.25V/2.4A power supply ... Load regulation: +/- 3%.
If that means it puts out 5.24V ±3% when connected to your Pi it means the output voltage could be as high as 5.4V which is higher than the 5.25V maximum recommended (5.0V ±5%).

Your supply might not put such a high voltage out and there may be losses in the cable. The Pi would probably be okay at 5.4V but you would have to check what maximum voltages were acceptable for anything you would be connecting to the Pi.

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bensimmo
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Wed Feb 01, 2017 7:27 pm

For the record, the Official PSU is 5.1V with +-5% regulation. So 5.36V max

Casimov
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Wed Feb 01, 2017 7:36 pm

hippy wrote:
Casimov wrote:5.25V/2.4A power supply ... Load regulation: +/- 3%.
If that means it puts out 5.24V ±3% when connected to your Pi it means the output voltage could be as high as 5.4V which is higher than the 5.25V maximum recommended (5.0V ±5%).
Hmm, Im wondering if I should just go back to the store and return the power supply. They told me that although it was the only one they had, that it would work fine with Raspberry Pi 3. And in fact, it says on the packaging for the product that its "Compatible with Raspberry Pi power requirements". So Im just confused, I dont wanna destroy my Pi, or anything I connect to it.
For the record, the Official PSU is 5.1V with +-5% regulation. So 5.36V max
So the max output that the official PSU can give is 5.36V, or 0.04 below the max output my PSU can give. This is a little bit more reassuring I suppose.

hippy
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Thu Feb 02, 2017 10:40 am

bensimmo wrote:For the record, the Official PSU is 5.1V with +-5% regulation. So 5.36V max
Which is above the 5.25V maximum recommended by the Foundation. Of course; it's not what the power supply puts out to the power cable but what the Pi and attached peripherals receive which is most important.

A higher than 5V supply is often recommended because that will overcome losses in the cable which has the Pi receiving a lower voltage. But if there is less loss in the cable the Pi will receive a higher voltage. It can all come down to the cable used whether a particular power supply is compatible with a Pi.

In the face of unknowns, the only thing which can really be said is; the higher the power supply voltage the more likely the maximum recommended voltage delivered to the Pi may be exceeded.

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RaTTuS
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Thu Feb 02, 2017 11:48 am

it is probably fine... however
as it has a wired in plug that will mean that the voltage is measured at the plug end - so voltage drop down the line is not considered...

you may get the poly fuse kicking in if anything goes untoward.....
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bensimmo
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Thu Feb 02, 2017 3:19 pm

RaTTuS wrote:it is probably fine... however
as it has a wired in plug that will mean that the voltage is measured at the plug end - so voltage drop down the line is not considered...

you may get the poly fuse kicking in if anything goes untoward.....
As is the official PSU.

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FTrevorGowen
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Thu Feb 02, 2017 8:18 pm

bensimmo wrote:
RaTTuS wrote:it is probably fine... however
as it has a wired in plug that will mean that the voltage is measured at the plug end - so voltage drop down the line is not considered...
you may get the poly fuse kicking in if anything goes untoward.....
As is the official PSU.
FWIW, measurements of the loading behaviour of the "original" (White, 5V 2A) "Official PSU" can be seen here:
http://www.cpmspectrepi.uk/raspberry_pi ... _Models.29
(albeit for a single sample)
But it should be noted, IIRC, that the 5V +/- 0.25V spec. applies to downstream USB device limits. AIUI the Pi's own "overvoltage" protection circuit's trip threshold is ~6V and the "low-voltage warning" threshold ~4.65V. Historically "Pi power issues" have been mainly associated with either units that have been designed to be chargers (and thus provide much less than 5V at their maximum currents) and/or connecting cables with too thin (high-resistance) conductors. Over-voltage tripping (and subsequent activation of the polyfuse) has been rarer and, IIRC, associated with the "accidental" use of something like a 9V or 12V PSU with "non-standard" cabling.
Trev.
Still running Raspbian Jessie or Stretch on some older Pi's (an A, B1, 2xB2, B+, P2B, 3xP0, P0W, 2xP3A+, P3B, B+, and a A+) but Buster on the P3B+, P4B's & P400. See: https://www.cpmspectrepi.uk/raspberry_pi/raspiidx.htm

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Burngate
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Re: Is a power supply of 5.25V/2.4A safe to use with RasPi 3

Fri Feb 03, 2017 6:03 pm

It's also worth noting that almost nothing on board uses the incoming power in its raw state - the chip uses 3v3 & 1v8 from a PAM2306AYPKE and VDD_core from a RT8088AWSC, and both of those can handle 6v5 (absolute maximum)

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