3x powersupply for rpi

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Re: 3x powersupply for rpi

Postby TommyBoy » 05 Feb 2017, 01:22

Image
my notes about how to connect power supplies
the ic is removed using two soldering irons, then it was easy,
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Re: 3x powersupply for rpi

Postby ritsjie1971 » 06 Feb 2017, 18:20

Very nice TommyBoy!

Actually I'm working on my linear psu too now. I'm gonna use the LT1963. I have to order the parts and then build it together.
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Re: 3x powersupply for rpi

Postby TommyBoy » 08 Feb 2017, 22:34

you are welcome.
please use as SHORT wires as possible, make room for large local caps like my picture show,
DOUBLE check your PI hardware before removing the original switcmode chip,
like measure the 1.8 and 3.3 and 5.0 volts at the locations i have shown.
different PI pcb versions exist, and they have moved the caps and caps numbers a little bit.
also very important to double check the voltages you make with the new regulators,
trim the two low voltages in as accurate as you can +/- 50mV and the 5V a bit to the high side,
like 5.05mV or 5.10V since your USB disk love a little bit to the high side for biggest margin to fail.

Another trick for noise hunters, see the cap near the USB connector, side of board, near IO pinrows ?
it is called C97 on my PI
it is mounted directly on USB power, after the 5V switch and measure system,
add a 1000-2200uF / 16V switch mode super duper grade cap accross this one,
now peak currents from usb disks cant enter your pi.

please share pictures, and results..
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Re: 3x powersupply for rpi

Postby ritsjie1971 » 22 Feb 2017, 16:26

20170218_213347.jpg
20170218_213347.jpg (145.58 KiB) Viewed 1708 times
My spare time is quite limited these days, as a lot of it goes to my photography hobby :-D

Anyway, I started with the power supply. The main linear supply is finished. With this, I'm gonna feed the stablizers for the 5V, 3V3 and 1V8.

I used a 6V transformer, 4 3A schottky diodes as rectifier, and 4 1500 μF in parallel for smoothing.
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Re: 3x powersupply for rpi

Postby ritsjie1971 » 22 Feb 2017, 16:27

Rectifier and smoothing elco's.
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Re: 3x powersupply for rpi

Postby ritsjie1971 » 22 Feb 2017, 16:37

Schematic, so far. No rocket science at all. Power On LED is not drawn here, but it's connected at the output right via a 470 Ohm resistor.
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Re: 3x powersupply for rpi

Postby pelliott321 » 23 Feb 2017, 02:32

Just one question
What is the resistor across the smoothing caps for? What is the value?
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Re: 3x powersupply for rpi

Postby ritsjie1971 » 23 Feb 2017, 10:42

pelliott321 wrote:Just one question
What is the resistor across the smoothing caps for? What is the value?


That's a 2k7 resistor, used to drain the voltage from the caps when no load is connected. Otherwise these caps will keep their charge. So the 2k7 is used to discharge these caps.
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Re: 3x powersupply for rpi

Postby TommyBoy » 28 Feb 2017, 14:33

what is your LOADED voltage at v-min measured with a scope ?
to be able to generate 5.00 stable, with no ripple the min pulse must be over 6V
so your trafo deliver too Low voltage,
use a 9V AC trafo and shotkey diodes will give correct range, then add a pre-regulator adjusted to 6V
this way your transfer a perfect DC supply into your critical unit, and this way it can make perfect 5V and all the other voltages,
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Re: 3x powersupply for rpi

Postby JohnC » 01 Mar 2017, 22:25

I went down the external DAC route with clean power supply (DIY) with good results. This way, so long it's USB DAC Audio Class 2 compliant, I can have better control of what chip to be used and this method works with Rune very well:

A) The following post has a very simple method to separate the power supply using a Y-split USB cable. It works like a charm:

http://www.head-fi.org/t/634760/resonessence-labs-concero-discussion-review-thead/1320
Go to Post #1326 for the illustration. It works great with iFi iDSD Micro for DSD or DXD files.

B) Another option is to use a DAC that separates the power for you. I personally find the HiFiMeDIY Sabre USB DAC 2 (External PSU) sounds good and have good value for general uses.

C) Lastly, the linear power supply mod for HiFiBerry DAC+ Pro is pretty straight forward. https://support.hifiberry.com/hc/en-us/articles/205732441-DAC-Pro-external-power-supply

John
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