5 volt USB power for Ipad charging noise on radio

[RFguy]

Hi Mike

left hand pic - attach cap across the two large circles. Yes just parallel the 10nF and 100nF caps.

 

right hand pic- attach cap across the two blobs , which is exactly in parallel with the large arrow electrolytic cap. 

if you have trouble getting in there, maybe attach 10nF to the top, 100nF underneath etc. 


the left hand pic showing the small circle and blob on the USB connector PCB- that is the power pins of the USB connector- you COULD add an extra 10nF there. 

[danny_galaga]

I know just enough about electronics to look generally ignorant- why is it they are using buck converters instead of voltage regulators for 12v down to 5v? I know buck converters generate really high voltage to do the conversion so it seems like a good way to create interference whereas the old solid state regulator should be quiet I would have thought.

[sfGnome]

2 hours ago, danny_galaga said:

why is it they are using buck converters instead of voltage regulators for 12v down to 5v?

Efficiency. If you’re pulling 2A from your converter, then the old linear converter will be dissipating 14W as heat, whereas the switching regulator will dissipate in the order of 100mW. Note, though, that not all switching regulators generate high voltages. For high efficiency, they do have very sharp edges on the switching signals, but that’s easy to control with careful design (and a little bit of extra money). 

[danny_galaga]

Gotcha. So for cars and planes, it's not really the wasted energy that is the problem per se, but the hassle of dissipating the excess heat? I first learnt something about the two types because I was fixing my Commodore 64 power supply. The old linear regulator would certainly keep your feet warm on a cold day 😄. But they were prone to going full voltage if they failed and instantly and silently killing your machine. I replaced it with a good quality USB charger. 

Edited August 4, 2022 by danny_galaga

[Blueadventures]

On 29/07/2022 at 7:58 PM, RFguy said:

so on the outer two pins of the USB connector, approx 1/4" leads no longer

that USB has a subboard- you'll need to get the cap wires across the USB pins .
and the input side- well that's easy, across the pair of spades

if you want to go to town a 10nF and a 100nF in parallel even better. 
https://www.jaycar.com.au/10nf-50vdc-ceramic-capacitors-pack-of-2/p/RC5348?pos=2&queryId=e517493d3ef57325d5af7d045f0b4676&sort=relevance
https://www.jaycar.com.au/100nf-50vdc-ceramic-capacitors-pack-of-2/p/RC5360?pos=3&queryId=644fcba3c794f9c5819969aec721cd51&sort=relevance

 

pics :
The input side caps go on those red circles.

you will see on the lower side the small dots on the USB connector PCB. there should be a better spot- that is to say the 5V will go up to the PCB, and it might be easier to put the caps on the main PCB, so (see the 2nd PCB) pic below
those two blocb  dots on the big cylindrical capacitor with the arrow, that is where you want to get the 5V output caps.... That part is leaded, so you'll be able to mount the caps on back OR front, just that on the back, the toroidal inductor might get in the way. I think the leads are right under the middle of the toroids hole ! you can move that toroidal inductor while you are soldering it in- dont worry about proximity , the inductor wont care about having a cap against it,

 

Fitted the 10nF size and will fit in Nynja tomorrow.   Could I have just fitted a single 100nF to each location?IMG_3887~photo.HEICIMG_3887~photo.HEICIMG_3890~photo.HEICIMG_3888~photo.HEIC

[RFguy]

sorry I cant read HEIC files... some new image format?

 

See how the 10nF goes- often you need both (10nF and 100nF) . depends exactly on the capacitor  characteristics and how they are mounted.

Edited August 13, 2022 by RFguy

[onetrack]

HEIC files are a stand-alone Apple photo format. You can get assistance to open them with Windows programmes. JPEG is a much more versatile format.

 

https://www.howtogeek.com/345504/how-to-open-heic-files-on-windows-or-convert-them-to-jpeg/

[Blueadventures]

18 minutes ago, RFguy said:

sorry I cant read HEIC files... some new image format?

 

See how the 10nF goes- often you need both (10nF and 100nF) . depends exactly on the capacitor  characteristics and how they are mounted.

Hate my iphone 13, (another reason) loved the samsung S9.  Just opened the images, in a paint file and saved as a jPeg. See if this works.

 

 

 

Edited August 13, 2022 by Blueadventures

[Blueadventures]

50 minutes ago, Blueadventures said:

Hate my iphone 13, (another reason) loved the samsung S9.  Just opened the images, in a paint file and saved as a jPeg. See if this works.

 

 

 

sent to email.  Samsung was easy and quick.

[Blueadventures]

On 29/07/2022 at 8:27 PM, RFguy said:

Hi Mike

left hand pic - attach cap across the two large circles. Yes just parallel the 10nF and 100nF caps.

 

right hand pic- attach cap across the two blobs , which is exactly in parallel with the large arrow electrolytic cap. 

if you have trouble getting in there, maybe attach 10nF to the top, 100nF underneath etc. 


the left hand pic showing the small circle and blob on the USB connector PCB- that is the power pins of the USB connector- you COULD add an extra 10nF there. 

Flew for 1.5 hours today with mini ipad on charge and no noise  so all good.  Didn't think to also put iphone on charge , will next time.  I did change the usb to each of the sockets and all good.  Thanks again for info.

[danny_galaga]

So I've read through this whole thread now, as I had joined half way. I've learnt from here that the 12v to 5v USB chargers use a buck converter, not a linear regulator. I hadn't realised these would cause so much interference to the radio although after reading through all this it makes sense. But I do know that you can get a pretty dirty voltage from cheap buck converters which may not be good for your expensive electronics. How dirty? Check out this article on wall warts

 

http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html?m=1

 

Granted, these are converting high AC to 5v DC so potentially have more problems with 'noise' but you get the idea. As Sully used to say - Oils ain't oils. Check out the oscilloscope readings for noise and voltage sag

😲

I have a cheapo USB in my panel already. I will keep it because it also has a voltmeter in it. But I'm going to experiment with an LM338 as per Kyle's post. That will be dedicated to my iPad/galaxy. I notice genuine LM338 are not cheap. But I figure a cheapo one should still be good for 2 amps.

Edited September 11, 2022 by danny_galaga

[Blueadventures]

On 29/07/2022 at 7:58 PM, RFguy said:

so on the outer two pins of the USB connector, approx 1/4" leads no longer

that USB has a subboard- you'll need to get the cap wires across the USB pins .
and the input side- well that's easy, across the pair of spades

if you want to go to town a 10nF and a 100nF in parallel even better. 
https://www.jaycar.com.au/10nf-50vdc-ceramic-capacitors-pack-of-2/p/RC5348?pos=2&queryId=e517493d3ef57325d5af7d045f0b4676&sort=relevance
https://www.jaycar.com.au/100nf-50vdc-ceramic-capacitors-pack-of-2/p/RC5360?pos=3&queryId=644fcba3c794f9c5819969aec721cd51&sort=relevance

 

pics :
The input side caps go on those red circles.

you will see on the lower side the small dots on the USB connector PCB. there should be a better spot- that is to say the 5V will go up to the PCB, and it might be easier to put the caps on the main PCB, so (see the 2nd PCB) pic below
those two blocb  dots on the big cylindrical capacitor with the arrow, that is where you want to get the 5V output caps.... That part is leaded, so you'll be able to mount the caps on back OR front, just that on the back, the toroidal inductor might get in the way. I think the leads are right under the middle of the toroids hole ! you can move that toroidal inductor while you are soldering it in- dont worry about proximity , the inductor wont care about having a cap against it,

 

Just some feedback foir RFguy and all.  This upgrade you mentioned has worked well over the weekends flight 9 hours and using to charge phone and mini ipad and no noise at any time.  Thanks again for the parts and where to solder them to.  Cheers.

[Carbon Canary]

Still interested in any feedback on this unit good or bad as seen in SportPilot.

 

https://www.flightstore.com.au/design4pilots-pilot-co-charger

[skippydiesel]

Shear luck I guess but I never had a problem with the off the shelf  "cigar/cigarette'plug  style iPad/ other devices chargers, sourced variously from JayCar / Woolies. Had up to 4 going at once.