Re: 12v->5v noise


N5XMT
 

Yep, depending on the pi.  Pi 3B requires 2A, 4B+ pi foundation says 3.5A.  add to that any USB devices and what they pull up to another amp, then you need a powered hub beyond that

On Sep 24, 2020, at 06:13, Randon Loeb <randonloeb18@...> wrote:
I had hoped that device would service all my usb needs, but I believe a pi needs 2-3 amps?

On Thu, Sep 24, 2020 at 1:42 AM Tom Flynn via groups.io <tflynn6693= aol.com@groups.io> wrote:
I think a 7805 puts out 1.5 amps his device puts out 15.  Does he need 15 amps?


On Sep 23, 2020, at 10:45 PM, Siegfried Jackstien < siegfried.jackstien@...> wrote:


If you have enough power... Use an7805
That sure is quiet even if it wastes some power in heat...
Sure its possible to make a switcher quiet... Meanwell psu are really good... But for shortwave i would additionally add some filters and ferrites.. If a switcher used... 
Or use 7805... Grin
Greetz dg9bfc sigi

Am 24.09.2020 05:16 schrieb Randon Loeb < randonloeb18@...>:
Was all excited to try my remote shack (rpi3 controlling ft-891 over wifi) but unlike my in-house testing with pi powered off a wall wart, when I power it off battery through a 12v->5v converter I get noise that (at least on 20m) raises an s1 floor to s9. Basically the rig is in my car powered off a lifepo (not the car battery), I mention because space is tight.

I believe it is mostly coming from the converter, this one:  https://www.amazon.com/gp/product/B07V7YY5X6/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

It seems to send noise through cables connected to it (well technically the usb power hub I made), but also through the pi and into the radio via the usb cat cable. But any cable plugged into seems to sort of act like an antenna.

If I power the pi off of a 5v cellphone battery pack, noise drops down (seems like maybe a little, but at least S6 floor drop). As I say, I tested this pi in close proximity to the radio before off a wallwart, so I don't think pi itself is creating the noise.
 
Only thing I want to mention is that I created my own little USB power hub to connect to the converter using some jacks I have, and I assumed it is correct or at least harmless to ground the usb jack cases, was that wrong?

For now I am assuming the converter is noisy.

Anybody have experience with that one? Is there a better go-to? Besides ferrites (will try in the morning) any other way to quiet this one down? I have a few buck converters lying around and will see if I can come up with something, but open to any suggestions.
Thanks,
Randy KN4YRM

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