A Tale of Two Power Supplies - why good is good and better is best
#1
Lightbulb 
The purpose of this post is to discuss two power supplies, and their ratings, why they are good, and why one is better.

   


The pic above shows two power supplies available on the market which may be used with the PineA64 (or the Raspberry PI, for that matter).  Both of these supplies are international supplies , which means they have interchangeable heads which match the mains of several different prominent world locations; these have been set to mains U.S. 120v AC.   The black PSU on the right is good, the white PSU on the left is better;  why?

The reason comes down to the AC rating (the size of the mains primary winding) the length of the cord, the gauge of the wiring in the cord, and the rating of the DC output volts & amps. The rating of the PSU is on the label ; the following pics show the labels of the two supplies high-lighting the positive attributes of each supply.

   

The black supply in the pic above is (good) has 22 AWG two conductor cable of reasonable length (about 1 meter) and is rated at the mains for .35 amps and provides an output of 5v @ 2.0A or 2000 ma. The higher the gauge number, the smaller the core diameter of each conductor and the less current it can carry effectively without adverse voltage drop. 22 AWG is good, but is not the best.  A range of 18-20 AWG is satisfactory, and 22 AWG is on the low side.  This power supply is only rated for .35 A on the mains side, and can only deliver 2000ma on the DC side at 5v. This also is 'good' for the PineA64 (or Raspberry PI 3) but is not the best.  

   

The pic above shows the Raspberry PI international PSU.  It has 18 AWG two conductor cable and is rated at the mains for .5A.  The DC rating of this supply is 5v @ 2.5A or 2500ma.  This supply is the best supply for the PineA64 (or the Raspberry PI 3) because even though its power cord is about 15cm longer, its core diameter two conductor cable is superior;  also the mains primary is beefier (.5 A) and its DC output is 500ma higher for the same voltage output of 5v.   

It is preferable to shorten the power cord of this supply (if possible) to further reduce the voltage drop which occurs with DC voltages transmitted over a distance (the shorter the cord, the better the stability of the switching supply). 

The white supply listed above is specifically listed as a 'switching' adapter; while the black supply shown above is not. This does not mean 'for sure' that it is NOT a switching supply, only that it is not rated as a 'switching' supply and may in fact be a linear supply.  A 'switching' adapter is more efficient than a linear supply, and better able to maintain a steady 5v at full rated current loads - 2500ma in this case.

This is in no way intended to be disparaging; it is intended to show what is available and high-light the differences.
marcushh777    Cool

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#2
Nice writeup Mark... I'm sure that will help a lot of new users. Maybe you can make this a sticky topic for this thread?

btw, I think you meant  18-20 above where you were talking about wire gauge... not  18-25 (i.e.  A range of 18-20 AWG is satisfactory).

Also switching vs linear, you can usually tell by weight. Most of the adapters that could be considered linear are simply a transformer (and are usually much heaver than switching power supplies), which is why the voltage drops as they are loaded up, as there is actually no regulation. An good example is the earlier modem power supplies, almost all of them (in this country at least) were just a AC 240v to 9v AC transformer.... the regulation happened in the modem. However, this was nowhere as efficient as switching power supplies, and wasn't the best when you needed heavy currents. Plus the dodgier ones got warm and used a lot of power when they weren't doing anything.
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#3
(08-10-2016, 12:19 AM)pfeerick Wrote: btw, I think you meant  18-20 above where you were talking about wire gauge... not  18-25 (i.e.  A range of 18-20 AWG is satisfactory).

doh !   You are absolutely correct... corrected.
marcushh777    Cool

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#4
Smile 
(08-10-2016, 12:30 AM)MarkHaysHarris777 Wrote:
(08-10-2016, 12:19 AM)pfeerick Wrote: btw, I think you meant  18-20 above where you were talking about wire gauge... not  18-25 (i.e.  A range of 18-20 AWG is satisfactory).

doh !   You are absolutely correct... corrected.

Just wanted to add the I purchased a Woonoo 5v 2.5a power supply on eBay for $13.  The product shipped with two Heat Sinks, one for the CPU and one for the GPU. Also the cord has an on, off button so the provided switch is not necessary.
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#5
(08-13-2016, 12:00 PM)Punkyclown Wrote:
(08-10-2016, 12:30 AM)MarkHaysHarris777 Wrote:
(08-10-2016, 12:19 AM)pfeerick Wrote: btw, I think you meant  18-20 above where you were talking about wire gauge... not  18-25 (i.e.  A range of 18-20 AWG is satisfactory).

doh !   You are absolutely correct... corrected.

Just wanted to add the I purchased a Woonoo 5v 2.5a power supply on eBay for $13.  The product shipped with two Heat Sinks, one for the CPU and one for the GPU. Also the cord has an on, off button so the provided switch is not necessary.

Punkyclown,

First, you posted so that your comments looked like mine... please don't put words in my mouth that way (no worries, I edited the post).  Thanks.

Second, the GPU is the CPU.  Actually, its a GPU with a CPU bolted on , so to speak  (it only requires ONE heatsink)


(the second heatsink you got is for the memory as it was intended for the Raspberry PI).

The switch for the PineA64 is absolutely required !  The switch on the PSU cable you bought is NOT the same thing. The switch on the PineA64 is attached to the PMIC (power management integrated circuit).  The Raspberry PI does not have a PMIC, and does not therefore need a power on button.  The power on button of the PineA64 is a multi-function switch for suspend|sleep, and power down.  The switch on your power cord will eventually destroy your SD card.  The power ON button of the PineA64 will cause the PMIC to signal the OS (interrupt event) to prompt for the power OFF dialogue.  In fact, this is the ONLY way to correctly power OFF Android... without the power ON button you cannot power OFF Android correctly;  and without the power ON button you cannot power OFF debian either without manually issuing the sudo poweroff command.

The electrical characteristics of the PSU you purchased are fine (assuming quality parts, and a good power cord, see above) but you paid too much for it.  The PSU I recommend in my post (above) is less expensive; leaving you a little money left over to buy the correct heatsinks for the PineA64 (and you need four of those) one for the GPU, two for the memory chips, and one for the PMIC.
marcushh777    Cool

please join us for a chat @  irc.pine64.xyz:6667   or ssl  irc.pine64.xyz:6697

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#6
(08-13-2016, 01:11 PM)MarkHaysHarris777 Wrote: Punkyclown,

First, you posted so that your comments looked like mine... please don't put words in my mouth that way (no worries, I edited the post).  Thanks.

....The electrical characteristics of the PSU you purchased are fine (assuming quality parts, and a good power cord, see above) but you paid too much for it. ...

Hi Mark,

Just a FYI as you probably didn't realise - there is an issue with the forum editor when you remove quotes on replying - if you inadvertently type in the quote box that is left behind it will put the "xyz said" bit back on top of your posting. I'm presuming that is what punkyclowns post looked like as I didn't see it. It's a bit annoying that you have to hit the 'view source' icon at the end of the editor toolbar to get rid of it... stupid editor.

Also, the MCM Raspberry pi adapter is $8.99 plus postage, whereas the eBay item was most likely including postage (and the heatsinks, but their cents in value). The total price of the MCM adapter with their 'super saving shipping' is  $16.98, so I think he came out well, assuming it can deliver the necessary voltage, etc! Big Grin And the inline power switch will be handy for starting up debian images without having to unplug/plug the microusb or adapter in - you just flick the switch both ways (unless you flicked it off when you shutdown the pine64).

Hey Punkyclown - can you give us a link to that item? I'm having trouble finding it...
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#7
No worries.   Big Grin
marcushh777    Cool

please join us for a chat @  irc.pine64.xyz:6667   or ssl  irc.pine64.xyz:6697

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#8
Sorry to bump an old thread, but I have had great success with the PWR+ brand 3.5 Amp power supply.  This supply was made for those netbooks that used micro-USB for power so it's exceptionally high-powered with lower resistance.  I use it for PINE A64 and Orange Pi/Raspberry Pi with fans and all kinds of bus-powered peripherals and never experience undervoltage warnings or SDCard corruption.
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#9
(01-03-2017, 11:20 PM)aegrotatio Wrote: Sorry to bump an old thread, but I have had great success with the PWR+ brand 3.5 Amp power supply.  This supply was made for those netbooks that used micro-USB for power so it's exceptionally high-powered with lower resistance.  I use it for PINE A64 and Orange Pi/Raspberry Pi with fans and all kinds of bus-powered peripherals and never experience undervoltage warnings or SDCard corruption.

The supply ( PSU ) is superb;  the problem is the micro-usb power connector;  it really doesn't do well with the required currents.  It is best to power the SBC Pine with the euler bus.

Read through this link completely.
marcushh777    Cool

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#10
(01-03-2017, 11:46 PM)MarkHaysHarris777 Wrote:
(01-03-2017, 11:20 PM)aegrotatio Wrote: Sorry to bump an old thread, but I have had great success with the PWR+ brand 3.5 Amp power supply.  This supply was made for those netbooks that used micro-USB for power so it's exceptionally high-powered with lower resistance.  I use it for PINE A64 and Orange Pi/Raspberry Pi with fans and all kinds of bus-powered peripherals and never experience undervoltage warnings or SDCard corruption.

The supply ( PSU ) is superb;  the problem is the micro-usb power connector;  it really doesn't do well with the required currents.  It is best to power the SBC Pine with the euler bus.

Read through this link completely.

I know, I read it, I am just reporting my (anecdotal) success using the micro-USB power connector using lots of power-drawing peripherals without any real problem.
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