Topics

12v->5v noise


Randon Loeb
 

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


Siegfried Jackstien
 

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


Tom Flynn
 

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


Randon Loeb
 

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


Pierre Martel
 

A pi4 need 3 amp just to run normally. not talking about any device powered by the USB or other power connector on the pi. 

A LM7805 will supply 1 amp max continuously and this is with a pretty large amount of dissipated power. If you go from 12v to 5v. just make the calcul of the power that it will need to dissipate. At 1 amp. 12-5= 7 volt times 1 amp = 7 watt that need to be dissipated.  I would go with a better designed buck converter circuit that will dissipate less power. and i would filter it a lot more by putting it in a grounded metal box with ferrite on the input and output wire and with small capacitor like 1uf or 0.1uf at the input and output also. 



Le jeu. 24 sept. 2020 à 09:13, Randon Loeb <randonloeb18@...> a écrit :
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


 

A Raspberry PI 4B can only accept 3 amps on it’s USB-C connector.  It does desire 5.1V though, not 5V.  
It’s tricky finding a 5.1V USB source that isn’t 110VAC powered.  

I have been using a switcher supply made by DROKing in the far east. 
This is a $15 or so device which has a multi-turn pot to set the output voltage and accepts a wide range of DC voltage on the input.  
A key feature is that when main power is turned on, the unit immediately outputs the desired voltage to the USB connector.  Some of the variable output USB converter items power on with the USB output disabled.  

The bug with this particular unit is that it appears that DROKing has discontinued it in favor of a menu driven device (at the same price) but which powers on with the USB output disabled.  However, the unit continues to be available in various places including Amazon.  However, for a while the ISBN number kept changing and so any link to the offering seemed temporary.  That sounds like somebody is cloning the device and it isn’t DROKing anymore.  Dunno.  Maybe DROKing changed their minds when the Internet blew up after they discontinued it?  


cc_buck_converter_pi_supply

I haven’t had any particular noise on HF from this, though I live in a suburb and have plenty of noise already.  YMMV. 

Tadd / KA2DEW
tadd@...
Raleigh NC  FM05pv

North Carolina Off-The-Grid Social Network: http://ncpacket.net/north_carolina_packet_radio_network.html
Packet networking over ham radio: http://tarpn.net/t/packet_radio_networking.html
Local Raleigh ham radio info: http://torborg.com/a





On Sep 24, 2020, at 12:38 AM, Tom Flynn via groups.io <tflynn6693@...> 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



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


N5XMT
 

Don't trust the voltage display on those.  Several people on our reef-pi forums for aquarium controllers set the display to 5v, then powered up the pi with it and smoked the pi... One was putting 12v out when the display showed 5v

On Sep 24, 2020, at 07:14, "Tadd KA2DEW in NC via groups.io" <mac.com@groups.io target=_blank>tadd=mac.com@groups.io> wrote:
A Raspberry PI 4B can only accept 3 amps on it’s USB-C connector.  It does desire 5.1V though, not 5V.  
It’s tricky finding a 5.1V USB source that isn’t 110VAC powered.  

I have been using a switcher supply made by DROKing in the far east. 
This is a $15 or so device which has a multi-turn pot to set the output voltage and accepts a wide range of DC voltage on the input.  
A key feature is that when main power is turned on, the unit immediately outputs the desired voltage to the USB connector.  Some of the variable output USB converter items power on with the USB output disabled.  

The bug with this particular unit is that it appears that DROKing has discontinued it in favor of a menu driven device (at the same price) but which powers on with the USB output disabled.  However, the unit continues to be available in various places including Amazon.  However, for a while the ISBN number kept changing and so any link to the offering seemed temporary.  That sounds like somebody is cloning the device and it isn’t DROKing anymore.  Dunno.  Maybe DROKing changed their minds when the Internet blew up after they discontinued it?  



I haven’t had any particular noise on HF from this, though I live in a suburb and have plenty of noise already.  YMMV. 

Tadd / KA2DEW
tadd@...
Raleigh NC  FM05pv

North Carolina Off-The-Grid Social Network:  http://ncpacket.net/north_carolina_packet_radio_network.html
Packet networking over ham radio:  http://tarpn.net/t/packet_radio_networking.html
Local Raleigh ham radio info:  http://torborg.com/a





On Sep 24, 2020, at 12:38 AM, Tom Flynn via groups.io < tflynn6693@...> 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



 

I haven’t had THAT happen yet.  Our local social-media-over-ham-radio project has about 40 of this model. I can attest that the output voltage display isn’t accurate though, as bad as +/- 0.2.  There is supposed to be a calibration procedure but I’ve never played with it.  The good news is that the output voltage doesn’t change on its own.  Once you set it to 5.1 or 5.2, it stays at where you set it.  I have a few USB test devices, one of which can put up to 4 amps load on a USB source, and others that measure the voltage and pass-thru current.  I recommend getting a USB voltmeter.  
Here’s an example of one for $12.  The 2 units I have weren’t anything special.
 
This will give you a clue of how bad the voltage swings on a USB cable when real current is drawn.  If you are getting the lightning bolt icon on your Raspberry PI GUI, this will explain why.  USB cables, unless they specify the wire gauge (and even then) use really crappy wire.  What kind of voltage drop would you expect drawing 3 amps across a 36 inch  24 gauge wire? 

This is a useful Linux command if playing with Raspberry PI supplies:

grep -a Under-voltage /var/log/syslog | tail -10


   Tadd

Tadd / KA2DEW
tadd@...
Raleigh NC  FM05pv

North Carolina Off-The-Grid Social Network: http://ncpacket.net/north_carolina_packet_radio_network.html
Packet networking over ham radio: http://tarpn.net/t/packet_radio_networking.html
Local Raleigh ham radio info: http://torborg.com/a

On Sep 24, 2020, at 10:50 AM, N5XMT <dacooley@...> wrote:

Don't trust the voltage display on those.  Several people on our reef-pi forums for aquarium controllers set the display to 5v, then powered up the pi with it and smoked the pi... One was putting 12v out when the display showed 5v

On Sep 24, 2020, at 07:14, "Tadd KA2DEW in NC via groups.io" <mac.com@groups.io target=_blank>tadd=mac.com@groups.io> wrote:
A Raspberry PI 4B can only accept 3 amps on it’s USB-C connector.  It does desire 5.1V though, not 5V.  
It’s tricky finding a 5.1V USB source that isn’t 110VAC powered.  

I have been using a switcher supply made by DROKing in the far east. 
This is a $15 or so device which has a multi-turn pot to set the output voltage and accepts a wide range of DC voltage on the input.  
A key feature is that when main power is turned on, the unit immediately outputs the desired voltage to the USB connector.  Some of the variable output USB converter items power on with the USB output disabled.  

The bug with this particular unit is that it appears that DROKing has discontinued it in favor of a menu driven device (at the same price) but which powers on with the USB output disabled.  However, the unit continues to be available in various places including Amazon.  However, for a while the ISBN number kept changing and so any link to the offering seemed temporary.  That sounds like somebody is cloning the device and it isn’t DROKing anymore.  Dunno.  Maybe DROKing changed their minds when the Internet blew up after they discontinued it?  



I haven’t had any particular noise on HF from this, though I live in a suburb and have plenty of noise already.  YMMV. 

Tadd / KA2DEW
tadd@...
Raleigh NC  FM05pv

North Carolina Off-The-Grid Social Network:  http://ncpacket.net/north_carolina_packet_radio_network.html
Packet networking over ham radio:  http://tarpn.net/t/packet_radio_networking.html
Local Raleigh ham radio info:  http://torborg.com/a





On Sep 24, 2020, at 12:38 AM, Tom Flynn via groups.io < tflynn6693@...> 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




w9ran
 

On 9/24/2020 9:47 AM, N5XMT wrote:
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
I'm running a USB-connected SDR and the two mini-fans that are part of the ventilated enclosure and that's all on a headless Pi 4.   To overcome endless throttling problems I have it connected to a 5V linear power supply that has a 10 turn trimpot voltage adjustment.    In order to keep the voltage above the point where throttling occurs I've got to adjust the power supply output to 5.5VDC to end up with 5.0 volts at the GPIO header.    I may as well separate the sense wires at the power supply and let it do the job automatically - having a voltage dropping resistor power cord went out of style in about 1940!

This is all due to the poor quality (high resistance) of the USB-C cables and IMHO, the poor choice of USB-C connector.   A powered hub with spread the load around but adds another device to what would be a clean solution if a proper power connection were provided to the Pi.  I'm also tempted to go back to feeding power into the GPIO pins but I reckon the power protection circuitry on the USB connector was put there for a reason.

73, Bob W9RAN


N5XMT
 

USB-C connectors can carry quite a bit of power.  Some laptops use them for the charging port.  Part of the issue is the Pi itself.  Granted, the USB spec states USB can supply 1.2A , but the Pi is limited to that as a total for all 4 ports. 

On Sep 24, 2020, at 08:11, w9ran <w9ran@...> wrote:
On 9/24/2020 9:47 AM, N5XMT wrote:
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

I'm running a USB-connected SDR and the two mini-fans that are part of
the ventilated enclosure and that's all on a headless Pi 4.   To
overcome endless throttling problems I have it connected to a 5V linear
power supply that has a 10 turn trimpot voltage adjustment.    In order
to keep the voltage above the point where throttling occurs I've got to
adjust the power supply output to 5.5VDC to end up with 5.0 volts at the
GPIO header.    I may as well separate the sense wires at the power
supply and let it do the job automatically - having a voltage dropping
resistor power cord went out of style in about 1940!

This is all due to the poor quality (high resistance) of the USB-C
cables and IMHO, the poor choice of USB-C connector.   A powered hub
with spread the load around but adds another device to what would be a
clean solution if a proper power connection were provided to the Pi. 
I'm also tempted to go back to feeding power into the GPIO pins but I
reckon the power protection circuitry on the USB connector was put there
for a reason.

73, Bob W9RAN







Randon Loeb
 

  Followup:

Thanks to all who replied.

And that with a usb cable with some ferrite wraps on it the noise seems to almost completely gone. I guess it was just a matter of finding a less noisy converter. Crazy watching the noise floor drop from s9 to s1 or 2.  Supposedly it can handle up  to 5A so should be good for powering the pi and a microcontroller I use for cw.

73 Randy KN4YRM


Dana KN4BEV
 

I believe 7805 is a 1.5 amp regulator, raspberry pi 3 would need closer to 2 amps (3 amps recommended) if using usb accessories. Not saying it wont work, because it probably will, but keep in mind the design restrictions.

Siegried is right though, a linear regulator produces no harmonic artifacts. Some DC converters are better than others, a search in this group would turn up various links and sources for quality low noise regulators.


On Wed, Sep 23, 2020 at 11:45 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



--


Randon Loeb
 

Can one simply use two 7805s in parallel? 

I'm not familiar with 7805 that one but I know with other regulators it is sometimes possible, sometimes not (or at least not without some additional balancing load resistors).

In any case I found a buck/boost in a drawer that seems very quiet though I did do a bunch of ferrite wraps on the output just in case.

73 Randy KN4YRM


Chuck M
 

I've used these for both 24 to 12 and 12 to 5 volts, RPi 3B supply.  Works well.  Haven't tried it with the RPi 4B yet.

On Sat, Sep 26, 2020 at 7:54 PM, Randon Loeb
<randonloeb18@...> wrote:
Can one simply use two 7805s in parallel? 

I'm not familiar with 7805 that one but I know with other regulators it is sometimes possible, sometimes not (or at least not without some additional balancing load resistors).

In any case I found a buck/boost in a drawer that seems very quiet though I did do a bunch of ferrite wraps on the output just in case.

73 Randy KN4YRM


Jim Higgins
 

Received from Randon Loeb at 9/26/2020 23:54 UTC:

Can one simply use two 7805s in parallel?

Not really the best thing to do, but if you must then you will need balancing resistors that are sized according to the difference in voltage between the two regulators. In practice, the resistors are sized based on the maximum theoretical voltage difference and that possible difference is based on device specs.

Link below is one way to do it, but you might want to use this link only as a starting place.

https://www.analog.com/en/technical-articles/paralleling-linear-regulators-made-easy.html

Personally I'd use a single more capable regulator rather than two, neither of which is capable alone. Even if you parallel two 7805 5-volt regulators the max current is 3 amps. Sure that works for most of us, but it's marginal, esp if the system is based on the RP4.

73 de Jim, KB3PU


Jim Higgins
 

Received from Chuck M via groups.io at 9/27/2020 00:02 UTC:

I've used these for both 24 to 12 and 12 to 5 volts, RPi 3B supply. Works well. Haven't tried it with the RPi 4B yet.

<https://www.amazon.com/dp/B01MQGMOKI/?coliid=IU4OS86NGX7J0&colid=1ZLJ6CRY1DUG4&psc=1&ref_=lv_ov_lig_dp_it>https://www.amazon.com/dp/B01MQGMOKI/?coliid=IU4OS86NGX7J0&colid=1ZLJ6CRY1DUG4&psc=1&ref_=lv_ov_lig_dp_it

Chuck
KD9DVB

Could work, but it's 3 amps MAXIMUM... and it can't be run without a load that approximates 10% of its rated output... meaning you need a resistor across the output to assure a load to prevent damage to the device. That's part of your 3 amp max, leaving 2.7 amp max of usable energy. Not enough in my book.

I'm not too excited about the idea of running something made in China and bought on-line six for $10 at its maximum specification... 2.7 usable amps in this case... which wouldn't be too hard to do in many of the applications mentioned here. Maybe it will turn out fine, but I'd rather have more margin.

What I want to know is why, even before the RP4, the sellers of RPis don't have a decent 5 or 6 amp supply at 5.1 volts with a nice heavy cord... like 3 feet long and #20 or even #18 AWG.

73 de Jim, KB3PU


Larry K8UT
 

Tom N1MM is using one of these to power a remote FreqEZ Band Decoder with its Pi-4 out at his tower. Advantage that it arrives with the Pi-4 connector on it. No reports of RFI from it.

https://www.amazon.com/gp/product/B086KTGRH1/ref=ox_sc_act_title_1?smid=A3OL48EYOMUID7&psc=1

Rated to 3 amps - should be sufficient. A Pi-4 2gb tested here draws 480 ma.

-larry (K8UT)

------ Original Message ------
From: "Jim Higgins" <HigginsJ@...>
To: RaspberryPi-4-HamRadio@groups.io
Sent: 2020-09-26 8:35:11 PM
Subject: Re: [RaspberryPi-4-HamRadio] 12v->5v noise

Received from Randon Loeb at 9/26/2020 23:54 UTC:

Can one simply use two 7805s in parallel?

Not really the best thing to do, but if you must then you will need balancing resistors that are sized according to the difference in voltage between the two regulators. In practice, the resistors are sized based on the maximum theoretical voltage difference and that possible difference is based on device specs.

Link below is one way to do it, but you might want to use this link only as a starting place.

https://www.analog.com/en/technical-articles/paralleling-linear-regulators-made-easy.html

Personally I'd use a single more capable regulator rather than two, neither of which is capable alone. Even if you parallel two 7805 5-volt regulators the max current is 3 amps. Sure that works for most of us, but it's marginal, esp if the system is based on the RP4.

73 de Jim, KB3PU








Don Melcher
 

I’m not seeing any noise from this

https://powerwerx.com/usbbuddy-powerpole-usb-converter-device-charger
--
Don
W6CZ


Dave Borcher
 

I use an LM338T. 5A, you can use it with any input voltage more than a couple volts above the desired output (and less than 36V). You need a couple of appropriate value resistors and a moderately-sized electrolytic capacitor that you wouldn't need with a 7805, but it's easy to calculate the resistors needed.  I will point out that you'd need to heatsink the device, and the greater the input - output voltage differential, the warmer the device can get also (which is of course the case with all series-pass regulators).  The 338 doesn't cost any more than the 317, which isn't much more than a 7805. The 317 / 338 devices have a lower output noise spec too.