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5V Power Converters
#1
Hi all,

I'm struggling with getting reliable, clean 5V supply for my system. In my latest OP iteration, I installed my RPI in a case designed to take my 250Gb SSD, and wired in the TOBSUN 10A buck converter that I had previously been using.

I had immediate problems, getting the lighting bolt on the PI screen frequently (low power). I measured output voltage and was only getting 4.5V under load. So, that got changed out to a 5A adjustable buck converter, which I adjusted to just over 5V output. The lightening bolts went away, and everything appeared to be okay.

I thought all was well until I noticed that my ships radio, with a masthead antenna, wasn't hearing VHF as well as my handheld in the cockpit! Clearly, the buck converter was generating so much noise that it was getting into my VHF! This is with 5 or 6 ferrite noise filters clamped over every power and signal wire I could find.

I have one other buck converter to try, but before I do, I'd like to hear what others are doing to get 5V for your systems.

Andy
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#2
i had power problems until i got a good usb hub"industrial grade" it takes 7 to 24 volts for power i use 12 and it powers the sdr pi and two arduinos.
mare liberum
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#3
Just an update on this. I just installed a new adjustable 12v to 5v buck converter. I moved it away from the radio equipment as much as possible, and grounded it to the boat's ground foil. I also grounded the metal case for my RPI, and installed a handful of ferrites on anything I could fined that was related to all this. My problem is mostly gone, although I can detect a slight change in VHF sensitivity when the OP system is powered up.

I guess the only other thing I could do would be to install a conventional voltage regulator instead of the buck converter, but it would consume considerably more current. So, for the moment, I'm going with this.

Here's the buck converter that I bought.

https://www.amazon.com/Regulator-DROK-Wa...B00CNXLDCQ
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#4
I use a BABC Big ass buck converter.. My pi gets power from a pico usb hat soon to be changed..
The pico would be good but support and updates, bugs make it a pain. it also uses a lot of i2c addresses.
I was wishing that OP would come out with a powerhat. I will probably make a hat to safely just send 5 v to 5vpin and some code to a button to do a safe shutdown/reboot. I don't like the mini usb it seems flaky.. more feeling then proof
I bought a 12v hub but as jim said it might be an issue being cheap.
Buck converters can be noisy. I dont know about grounding it to the boat.. Lighting protection should be separate. I thought that only that should be sent to true ground.. The motor is a separate ground with an anode. I have had a Buck converter go nuts and meltdown in a electrical box... scary...

I heard some good news today Canada has finished its border wall in 21 days. It is amazing what a few thousand crazy Canucks can do with snow blowers and beer. But what do i know I sail out of the drunken river and our best landmark is the where the make crown royal. Strange but true..
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#5
I used during 4 weeks last summer without any problem this XL4015 based DC-DC Step Down Adjustable Power Supply Module.
I got a fistfull of these (5) for less than 10 € ebay.fr
I set them to 5,24 VDC, I stopped the screw of the potentiometer with nail varnish, add 2 drop of hot glue to mechanically strengthen the coil, then two sprays of Tropicoat on each side, install and forget ...
I guess the strong coil is responsible of the smooth functioning...
They are easy to install in my PiDesktop case, and benefit from the fan ventilation.
I use a second one to power both the LCD screen and USB hub...
Performance Parameters (suppliyer data) :

1、Input voltage range:4~38VDC (Note:input voltage not Exceeding 38V)
2、Output voltage range:1.25-36VDC Adjustable
3、Output current: 0-5A
4、Output power: 75W
5、High efficiency up to 96%
6、Built in thermal Shutdown function
7、Built in current limit function
8、Built in output short protection function
9、Input reverse polarity protection: None (if required, high current diode in series with the input).
Config : RPi 3B+, OP 1.2
Cordialement
Didier B





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#6
Hello, everybody,
I would like to know how these converters behave with the Moitessier-hat.
What does rooco say. How high is the noise?
Which is the best wiring with which converter according to his test.
Greetings Jürgen
Angel  Entschuldigung für mein Englisch. Es ist "google english"
PN bitte auf german.  Big Grin
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#7
(01-11-2019, 03:45 PM)abarrow Wrote: Just an update on this. I just installed a new adjustable 12v to 5v buck converter. I moved it away from the radio equipment as much as possible, and grounded it to the boat's ground foil. I also grounded the metal case for my RPI, and installed a handful of ferrites on anything I could fined that was related to all this. My problem is mostly gone, although I can detect a slight change in VHF sensitivity when the OP system is powered up.

I guess the only other thing I could do would be to install a conventional voltage regulator instead of the buck converter, but it would consume considerably more current. So, for the moment, I'm going with this.

Here's the buck converter that I bought.

https://www.amazon.com/Regulator-DROK-Wa...B00CNXLDCQ

Andy, try a common mode choke. Normal DC/DC converters do not have filters to block switching noise
from the 12 V system. It may help to add capacitors or LC Filters but this is the wrong way. 

Because the LC Filter can have influence to the DC/DC switcher. It works perfectly if it is designed by the 
switcher developer himself. He has to add caps and Rs to stabilize the control loop.

What you can always do is to add a common mode choke. Two wires wound up to a ferrite/iron powder
ring. Add 10uF ceramic on both ends of the choke. This should reduce the switching noise dramatically.

All the best,
Chris
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#8
Excellent suggestion. I think I have those parts in the junk box. I'll definitely give it a try.

Thanks!
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#9
Just a simple idea is to adjust to 5.5v output, and use a LDO to supply 5v from 5.5v. This should give a much cleaner 5 volts if it really is affecting radio reception. For me the motessier hat seems to work fine without all of this, but I only care to see targets from up to 5 miles away anyway.

It won't block noise going to the 12 volt side. For this you would need to add filters on the 12v side.
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#10
Thanks Sean,
My impression is that the noise is coming from the 12V side and from the buck converter itself. I found a paper on the Internet about that type of noise from a buck converter, and potential solutions from a circuit design point of view. When I changed out the converter for one that was encased in metal, then grounded it, a great deal of the noise disappeared. When I further filtered both 12 and 5v sides with clamp-on ferrites and grounded the RPI case and the buck converter, the noise reached a "livable" point. I've ordered a few common mode filters from China to see how much more difference they make.

In interesting thought to implement a conventional regulator after the buck converter, although if the noise truly is common mode, I would think that it would still make it through.

I guess I should find a scope with a high enough frequency range to do some real scientific testing... then again, perhaps I should put down the soldering iron and go sailing!
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