LTolledo
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Powering my RPi projects using buck converters

Wed Feb 26, 2020 12:17 pm

In this post I'll compile all of my RPi projects powered by buck converters
but first I'll show what I used:
Buck Converters for RPi projects.jpg
Buck Converters for RPi projects.jpg (180.7 KiB) Viewed 1135 times
the "bare" buck converters can be seen on the right (middle and bottom).
as well as and how those were deployed in universal PCBs.

the top right is my first use of a buck converter on my RPi project, for a RPi4B-2G NAS with 2 x 8TB 3.5" HDDs
RPi4B-2GNAS_top.jpg
RPi4B-2GNAS_top.jpg (253.41 KiB) Viewed 1135 times
the buck converter board can be seen on the right side of the HDDs
the RPi4B power is supplied thru a connector soldered on the RPi board.
supply voltage set at 5.1v as measured using DVM.
another small buck converter can be seen on the HDD's left side, its to power the 12v case fan at 9v.
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LTolledo
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Re: Powering my RPi projects using buck converters

Wed Feb 26, 2020 12:23 pm

Another configuration of the same buck converter can be seen on the top left of the first image.
This too is used for another RPi4B-2G project, I call as RPi4B-2G hwRAID NAS project.
RPi4B-2GHWRaid.jpg
RPi4B-2GHWRaid.jpg (115.21 KiB) Viewed 1128 times
and a bit of a closer look:
RPi4B-2G-buck-view1.jpg
RPi4B-2G-buck-view1.jpg (76.67 KiB) Viewed 1128 times
a single 12v power brick supplies power to the USB hardware RAID box and the RPi4B-2G with a buck converter board.
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

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LTolledo
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Re: Powering my RPi projects using buck converters

Wed Feb 26, 2020 12:36 pm

Then I tried using a smaller buck size converter (inspired from the powering RPiZeroW using 24v topic)
so the small sized buck converters are (from the first image of the first post) is the bottom right (3rd and 2nd from bottom right)
its the same buck converter that I used to power the 12v fan mentioned in my 2nd post.

but before deploying those for RPi use, I need to confirm if it can really power an SBC.
my test bed for this was NanoPi Neo 2
buck-converter powered sbc.jpg
buck-converter powered sbc.jpg (126.28 KiB) Viewed 1119 times
seen on the left is a midget one, but it has 2 x 64GB USB thumb drives (additional 2-port USB 2.0 sockets soldered on the bottom PCB)

the right one is "loaded" with a single 1TB 2.5" HDD....

these worked fine..... so I guess its OK to power an RPi board

the last test was making another unit, this time with 2 x 1TB HDD and 1 x USB WiFi adapter
ran it for 3 days straight and accessed some media files from it.
no problems.... so off to the next
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

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LTolledo
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Re: Powering my RPi projects using buck converters

Wed Feb 26, 2020 12:46 pm

Yesterday I made the latest "module", its the bottom left one (from the first image of the first post).

Initial test on an RPi1B+ (my BreadboardPi). Voltage output set at 5.05v this time.
RPi Buck Converter board.jpg
RPi Buck Converter board.jpg (172.37 KiB) Viewed 1105 times
and it worked as expected.
the setup was connected to an HDMI monitor, with keyboard and mouse, Ethernet LAN connection
not even once did the lightning icon appeared.....
(maybe am not loading it hard enough?)

so then I tried booting it (Raspbian Buster full desktop) with an additional 1 x 80GB HDD in PATA to USB2.0 case, and a 16GB USB flash drive....
Buck Converter powered RPi with PATA HDD.jpg
Buck Converter powered RPi with PATA HDD.jpg (189.18 KiB) Viewed 1105 times
not even once did the lightning icon appeared.
yes... I did tried to access the HDD, and watched some videos (using the very rarely used VLC) stored on the HDD....
all's fine.... no lightning icon.... so no problem.
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
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LTolledo
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Re: Powering my RPi projects using buck converters

Wed Feb 26, 2020 12:53 pm

And just a while I tested the same buck converter module on an RPi4B-4G,
prior to boot up I've already attached a 2.5" 2TB HDD in SATA to USB3.0 case,
as well as HDMI monitor, Ethernet LAN, keyboard and mouse.
Buck converter test RPi4B-4G with HDD.jpg
Buck converter test RPi4B-4G with HDD.jpg (178.96 KiB) Viewed 1094 times
Buck converter test RP4B-4G with HDD view1.jpg
Buck converter test RP4B-4G with HDD view1.jpg (166.67 KiB) Viewed 1094 times
Buck converter test RPi4B-4G with HDD view2.jpg
Buck converter test RPi4B-4G with HDD view2.jpg (148.73 KiB) Viewed 1094 times
so that "small sized" buck converter is even able to power this setup.

I think I'll be building a few more...... ;)
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

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sora03
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Re: Powering my RPi projects using buck converters

Thu Feb 27, 2020 2:38 pm

Nice build but based on the photos, you seem to bypass the polyfuse of the Pi's? Is it not dangerous to do so.

I too used the MP1584 for my Pi 3B+, no problems with undervoltage ( as long as you use thick microUSB cables), I do not want to bypass the polyfuse.
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rpdom
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Re: Powering my RPi projects using buck converters

Thu Feb 27, 2020 2:54 pm

sora03 wrote:
Thu Feb 27, 2020 2:38 pm
Nice build but based on the photos, you seem to bypass the polyfuse of the Pi's?
The Pi 4B does not have a polyfuse.

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Re: Powering my RPi projects using buck converters

Thu Feb 27, 2020 3:05 pm

rpdom wrote:
Thu Feb 27, 2020 2:54 pm
sora03 wrote:
Thu Feb 27, 2020 2:38 pm
Nice build but based on the photos, you seem to bypass the polyfuse of the Pi's?
The Pi 4B does not have a polyfuse.
Good to know, is there still any protection from over current (or other danger)? (Does this mean it is safe to bypass my Pi 3B+ polyfuse?)
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rpdom
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Re: Powering my RPi projects using buck converters

Thu Feb 27, 2020 3:15 pm

sora03 wrote:
Thu Feb 27, 2020 3:05 pm
rpdom wrote:
Thu Feb 27, 2020 2:54 pm
sora03 wrote:
Thu Feb 27, 2020 2:38 pm
Nice build but based on the photos, you seem to bypass the polyfuse of the Pi's?
The Pi 4B does not have a polyfuse.
Good to know, is there still any protection from over current (or other danger)? (Does this mean it is safe to bypass my Pi 3B+ polyfuse?)
Have a look at the documentation. The partial Schematics show the power input circuitry. The Pi 4B still has the overvoltage protection diode, but without the fuse it will probably go short circuit (even with the fuse they sometimes did that). It is there to prevent your house burning down, not really to save the Pi from problems.

It has always been "safe" to bypass the polyfuse, just make sure you have a stable power supply.

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davidcoton
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Re: Powering my RPi projects using buck converters

Thu Feb 27, 2020 3:37 pm

The polyfuse (on Pi1, 2, 3 models) will protect the TVS diode, so should you apply the wrong voltage through supply fault or user error, the polyfuse may trip before the TVS melts. The anecdotal evidence is that the TVS usually fails SC, which is a repairable fault. However, on the Pi4 (or earlier models if the polyfuse is bypassed) this relies on the PSU itself being limited to a current that will not damage the Pi's power connector and tracks. This is required even under PSU fault conditions.

I would always recommend an external polyfuse for supplies with a current capacity greater than 3A.
I would be inclined to use one whenever powering a Pi from a non-RPT supply, but then I'm a cautious engineer.
I do not wish to imply that the RPT supply is either "safe"or "unsafe" in this respect, since I have no detailed knowledge on this point.
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LTolledo
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Re: Powering my RPi projects using buck converters

Wed Mar 04, 2020 1:27 pm

here is the latest one am working on... just finished the layouting.
buck converter top board v3.0 WIP.jpg
buck converter top board v3.0 WIP.jpg (169.42 KiB) Viewed 849 times

everthing has not yet been soldered yet.... still contemplating if am going to add a few more components and/or functionality......
the fan position is final though (opening and mounting holes already processed)....
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

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pi-anazazi
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Re: Powering my RPi projects using buck converters

Wed Mar 04, 2020 3:56 pm

I'm using a
LM2596 DC-DC HW 411
with a 12V/2A power supply with a raspi 2 v1.2 and 2x 1TB SSD with SATA-USB3 adapters (no further power supply for SSDs).

Running just fine, but I see some (frequent) untervoltage in dmesg. The NAS is working flawlessly. Will replace the power supply by a 12V/4.17A and much thicker cable for the 5.2V supply. Currently I have on the low-voltage ca. 20 cm of a small copper cable. I yesterday measured that for 10m of this cable I get 900mOhm...
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emma1997
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Re: Powering my RPi projects using buck converters

Wed Mar 04, 2020 7:36 pm

900 milliohms is terrible for a cable. Most likely your problem.

Personally I never ignore the Lightening Bolt of Death these days. A friend of mine did and also not bothered by the HD clickety clicking a lot even when not accessed. Eventually he lived to regret it when one drive died forever taking irreplaceable data with it. Sometimes I do learn from the mistakes of others.

Also be aware not all buck converters are the same. Little tiny cheapies from Ebay work great for my Pi0 but the same ones big trouble for Pi4. HolyTolledo uses small but top quality models which cost more but probably worth it for critical applications. Personally, being the cheesiest miser on the planet, do like to gamble for fun but not where it counts. IMO sometimes good to have a bit of a safety margin.

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pi-anazazi
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Re: Powering my RPi projects using buck converters

Wed Mar 04, 2020 8:13 pm

The 900mOhm are for 10m, so 90mOhm per m. Not good, though... it was my first try... :)

What is cheap, what is expensive für these converters? My bucks look pretty much identical to the one in the OP on the right top. Always willing to experiment.

https://www.amazon.com/LM2596-Converter ... B008BHAV4Y

The two SSDs are RAID1 and currently I use the NAS basically as an additional, off-site backup for experiments with rsync etc.
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Re: Powering my RPi projects using buck converters

Wed Mar 04, 2020 10:01 pm

For my Arduino type projects 0.1ohm/m is ok but for Pi about 10x better is better. What gauge is it?

As far as switchers IMO yours is middle of the road capable and not something I would personally use for Pi4 or original Pi3. Most of those LM2596 type seemed to work ok with Pi3b+ and at first even Pi4 but after a few hours or days the lightening bolt started to show up. Not all and some more often than others.

See my 1st photo. First two same as LTolledo. Tiny one 5/$1 on Ebay and only good for Pi0 IME. Middle one LM2596 2/$1 failed often with bigger Pi but not immediately. I suspect there may be some product culling here and seconds sold cheaper.

It's not so much the chip as the inductor and caps. PCB layout too. See my 2nd photo for an example how tricky these chinese sellers can be when it comes to cutting corners. Notice how much bigger the top toroid is compared to the bottom, otherwise identical unit. And the heat sink too although putting one on top of an IC like that has relatively little benefit.

That last one on the right (XL4015 chip) is the only version found to be reliable across all my Pi models. In fact ok for up to 4 portable USB drives but some extreme wiring measures needed as mentioned in my old post. They used to be less than $1 ea shipped and not much more now even with tariff war and virus:

https://www.ebay.com/itm/DC-DC-Buck-Ste ... 2749.l2649
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pi-anazazi
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Re: Powering my RPi projects using buck converters

Thu Mar 05, 2020 8:47 am

The cable is Märklin 7101 (and other colors...), no idea how to measure the gauge of the copper accurately ;-) ((PS: Found in Amazon product description: "Width 0.19 mm2", so somewhere inbetween AWG 24-25)).

But definitely multiple times the diameter of copper compared to a number of USB cables I cut to power Raspis via GPIO pins in the past. So I thought it would be all right to give it a try.

Undervoltage is about every 9-17 min and normalises within 5-6 seconds, according to dmesg. I turned off HDMI now to safe some power (30 mA?), currently I rsync some hundred GB over a VPN tunnel to a remote NAS, but there is no real load on the CPU of the raspi 2 (v1.2)...

PS: Your XL4015 would be "item 1" (with cooling) or "item 5" (without cooling) from here, I guess:

https://www.ebay.de/itm/XL4015-5A-DC-DC ... 2472609079
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LTolledo
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Re: Powering my RPi projects using buck converters

Thu Mar 05, 2020 11:11 am

On my RPi4B-2G NAS, I used 20AWG stranded wires to supply power from the buck converter.

started the NAS above this morning, and checked the dmesg after 12 hours.... no "complaints" about power
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

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pi-anazazi
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Re: Powering my RPi projects using buck converters

Thu Mar 05, 2020 1:43 pm

This was my first try for a "single-power-source" NAS powered only via the raspi. I don't need the USB3-throughput, bottle neck is the DSL line. That's why I cose a raspi 2 and 2x Samsung SSD 1TB (not that high power consumption, compared to WD red HDDs I usually use).

I measured the 5.2V output at the end of the thin, low-voltage cables iirc. But maybe things change under load. I guess there is no way to show the acutal voltage at the pi, as usually possible in BIOS of larger boards?
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Re: Powering my RPi projects using buck converters

Fri Mar 06, 2020 8:21 am

@LTolledo

Would you mind showning some details how you connect the AWG20 to the connectors for the GPIO-pins? :-)

I now soldered a solution, but it's far from optimal...
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Re: Powering my RPi projects using buck converters

Fri Mar 06, 2020 10:31 am

PS: One reason I chose the blue Märklin cable is the fact, that the official power supply for the Odroid XU4 (5v 4A power supply...) doesn't look better at all (black cable, see photo attached) and I never had any problems with this.
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karrika
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Re: Powering my RPi projects using buck converters

Fri Mar 06, 2020 11:37 am

These buck converters look very familiar.

There is one problem in using them. They create a lot of high frequency noise on the 5V power line. I have never been able to use these converter with the 7" official touch screen. The display image looks ok. But the touch screen part refuses to work. Adding extra filtering after the converter does not help either.

I have tried these with multiple Pi's and multiple 7" Official screens.

In any case I rather use the official PSU as it produces clean power.

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pi-anazazi
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Re: Powering my RPi projects using buck converters

Fri Mar 06, 2020 12:13 pm

Point is: I have so many 12v power supplies (bought with SATA-USB adapters with extra power supply for the HDD) I simply want to find a way to use them ;-)
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LTolledo
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Re: Powering my RPi projects using buck converters

Fri Mar 06, 2020 2:19 pm

pi-anazazi wrote:
Fri Mar 06, 2020 8:21 am
@LTolledo

Would you mind showning some details how you connect the AWG20 to the connectors for the GPIO-pins? :-)

I now soldered a solution, but it's far from optimal...
This is probably the best that I can give you... its the setup before getting the RPi4B-2G into the armor case.
RPi4B-2G-buck view2.jpg
RPi4B-2G-buck view2.jpg (162.38 KiB) Viewed 495 times

the red and dark-gray wires are the 5.1v and Gnd wires respectively, connected to buck converter module using XH connectors
on the RPi side, the wires are soldered to TP1 and TP7 (5v and Gnd, respectively).
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

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pi-anazazi
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Re: Powering my RPi projects using buck converters

Fri Mar 06, 2020 3:11 pm

OK! So you solder the cables directly to the pins. Interesting...

I solder the cable to the crimp pin connector, somethink like this

https://docs.rs-online.com/b1d7/0900766b80d9c84e.pdf

So I can have the plastic housing around the crimp pin, then I have

- electric isolation

- can change the power supply easily

- avoid mixing up - and +, as I use a two-pin plastic housing for + pin and a single one for ground.
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LTolledo
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Re: Powering my RPi projects using buck converters

Sat Mar 07, 2020 1:26 am

pi-anazazi wrote:
Fri Mar 06, 2020 3:11 pm
OK! So you solder the cables directly to the pins
No, I dont solder to the GPIO header pins... as I want the GPIO headers always available for HATS like DACs, etc
I solder wires to the TP at the back side of the board.
RPi4B TP solder points.jpg
RPi4B TP solder points.jpg (58.26 KiB) Viewed 449 times

for the RPi3B+, also on the back side. on these boards, its called PP
seen below are the solder points, but used to extract 5v for fan power.
RPi3B+FanPower.jpg
RPi3B+FanPower.jpg (195.21 KiB) Viewed 444 times
"Don't come to me with 'issues' for I don't know how to deal with those
Come to me with 'problems' and I'll help you find solutions"

Some people be like:
"Help me! Am drowning! But dont you dare touch me nor come near me!"

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