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SteinAir Dual USB Max Current

mosquito

Well Known Member
Hi,

I'm confused by the specs on SteinAir's double USB offering, here: http://www.steinair.com/product/dual-usb-panel-jack/

Does anyone know if I should plan for max 2.1A draw from this unit, or 4.2A?

>> For 12 volt and 24 volt DC electrical systems, 2.1 amps max.

OK that makes me think 2.1A.

>> Two 5 volt 2.1 amp USB power jacks with an LED indicator.

Hmmm that could be 4.2A.

Color me confused. Anyone know? Thanks!

-jon
 
5V * 2.1A=10.5 watts * 2 ports = 21 watts

21W / 28V = .75 amps

21W / 14V = 1.5 amps

There will be a bit of loss in 'translation' for a switching power supply to convert bus voltage to 5V. If it's an analog regulator, quite a bit more loss.

Charlie
 
5V * 2.1A=10.5 watts * 2 ports = 21 watts

21W / 28V = .75 amps

21W / 14V = 1.5 amps

There will be a bit of loss in 'translation' for a switching power supply to convert bus voltage to 5V. If it's an analog regulator, quite a bit more loss.

Charlie

Oh my, color me embarrased now, I've forgotten so very much. THANK YOU!

-jon
 
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Fyi

FYI these exact USB chargers are available elsewhere (eBay amazon) for a fraction the price. Kinda felt ripped off when I saw them for 7$ vs 40$ I paid at Oshkosh from Stein.
 
FYI these exact USB chargers are available elsewhere (eBay amazon) for a fraction the price. Kinda felt ripped off when I saw them for 7$ vs 40$ I paid at Oshkosh from Stein.

I'm always up for a deal, but be sure you're comparing apples to apples. Most USB chargers are 'switchers'. They take bus DC voltage, feed it into an oscillator that runs at a relatively high frequency to make a rather nasty square wave, and step the voltage to the desired voltage before rectifying back to DC (5 V in this case) for the USB supply. Not all switchers are created equal. Some are very quiet; some are quite 'noisy' in terms of audio and/or RF interference because the square wave output of the oscillator is fairly hard ($$) to filter back to pure DC that contains no noise.

There are probably some $7 units that are quiet, but rest assured that many, even at higher price points, are not.
 
In some of the automotive forums (Honda) they talk about issues with the TPMS signals from the wheels getting interfered with by cheap 12V cell phone USB charger. My wife was getting TPMS faults until we got rid of her cheap EBay USB charger and the errors stopped immediately so there is validity to these cheap USB adapters being noisy.
 
FYI these exact USB chargers are available elsewhere (eBay amazon) for a fraction the price. Kinda felt ripped off when I saw them for 7$ vs 40$ I paid at Oshkosh from Stein.

Still a lot less then aircraft spruce has USB ports for $200-$400. What makes them so expensive? Are they any better/quieter? Are they blessed by some government agency?
 
I ran into the RFI problem when sourcing power adapters for my recent Stratux/Nexus install. The Chinese look-alike to the Stein port was noisy as was a couple of adapters I purchased at local auto parts stores.

But somehow I lucked up and found a $5 adapter at Walmart that is silent and will charge the Nexus 7. I have no idea why this cheapo adapter works well and the others didn't.
 
After going through 3-4 chargers for my car, a little research turned up Commit panel charger. The site has much background information on USB chargers that would be helpful in making a selection. Where to mount it is another decision.

Stein was not selling at the time I purchased. I spent a third of the cost of my plane with Stein. Tools, parts, panel, it all works. Trustworthy. Not a single regret.
 
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i did some studying before i bought my usb port. bottom line is that we are pretty much at the mercy of the supplier. a port may or may not be quiet and you don't know until you try it. in the end i bought stein's. a supplier that will stand behind his word [that it will be quiet] . and since i cut a hole in the panel for the port i wanted to get it right the first time.
 
FYI these exact USB chargers are available elsewhere (eBay amazon) for a fraction the price. Kinda felt ripped off when I saw them for 7$ vs 40$ I paid at Oshkosh from Stein.

Except they're not...when you buy them from those other places, I'm fairly certain (but not entirely sure) that they don't open them up, modify them and then put them back together like we do?

Assumptions can be quirky things...because sometimes things are not always as they seem based on pictures from the interwebs. We do modify them for reasons discussed in this thread - what do we do to them? Well, that's the $33 question! :)

Cheers,
Stein
 
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I'm still a little confused as to the amp situation. I recently just installed a Stein in back and PowerWerx one in front. I thought initially I needed to use a 5amp fuse for the total 4.2 amps....but I've seen that it says use a 3 amp fuse in one of the instructions. Is this correct!? In my EXTREMELY limited knowledge I would think you add the amperage to determine the fuse and wire used. So it's not 4.2 amps? When you look at the USB charger on Spruce it says "4.2 Amp Dual USB"

http://www.aircraftspruce.com/catalog/elpages/eadualusbpanel.php

So if 4.2 Amps is flowing to the chargers, is it not also flowing through the lead wire? Pardon my ignorance here. I learn by asking a lot of stupid questions.

Wingnut
 
Power in Watts is Volts x Amps, so Amps is Watts / volts

The usb charger has the ability to output a total of 4.2 amps x 5 USB volts, 21 Watts.

Power conversion is not perfectly efficient so round up to say 24 watts needed to power the USB charger from the plane.

24W at aircraft bus's 12V = 2 amps, call it 2 Amps the supply side.
If you had a 24v aircraft bus, the charger would draw 1 amp.

Wiring and protecting for 3 amps makes sense.
 
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Edit: stand by... I had a strange rpm anomaly today and my USB port is right above the p-leads going to my ignition switch. Will do some more testing in the next day or so and see if there's any correlation. Will report back.

For what it's worth, I've just installed the "Cllena Dual USB Charger Socket Power Outlet 2.1A & 2.1A for Car Boat Marine Mobile (4.2A-Blue)"
https://www.amazon.com/gp/product/B01HPSY596/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1 and have no noise whatsoever. Radio transmit out is also loud and clear.

Your installation may be different than mine, the consistency of quality from this supplier may change from one order to the next, so YMMV. However, worked great for me at a fairly reasonable cost.

Hope this helps.
 
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Any issue with that blue light being too bright? Also, should I use shielded wire or is the noise from the unit itself?
 
USB noise

Ref rv7charlie's comments above-

I have front & back dual USB chargers in my RV-4 that I got el cheepo off the internet with the little blue LED indicators. I installed them to power my Garmin VIRB Ultra 30 while simultaneously plugged into a headphone jack to record & power the camera while filming (can't do this with a GoPro). All works well but when I view the recording there is a buzz in the audio. It does work and records audio just fine with the exception of the very annoying buzz. At first I though it was the cable I had made from Pilot Communications. I tried it in the USB port in my car it it was crystal clear.

So yes there's noise unless it is designed to be electronically quiet. I just ordered a pair of USB jacks to replace mine from Stein that does not have the LED light so I think my problem will be solved.
 
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