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  #11  
Old 06-13-2012, 02:54 PM
N1593Y N1593Y is offline
 
Join Date: May 2008
Location: Sisters, OR
Posts: 98
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There is a lot more to this than meets the eye.

USB powering depends on the device being powered.

When telephones started charging on USB ports, they used no more than 1/2 amp which was about what the USB 1.0 spec provided.

Then along came tablets that now can draw a little over 2 amps which exceeds even what the USB 2.0 spec provides for power. So the tablet wall wort charges have some circuitry in them to figure out that a tablet is plugged in and it will supply the full current for "rapid" charging, but when you plug the tablet into a normal USB port on your computer, the tablet only trickle charges. Unfortunately the tablet makers don't have a standard for the full power sensing circuitry so a charger for one tablet may not work to charge another brand of tablet, even though the charger socket is a USB connector. You must use a proprietary cheater cable for the tablet of choice to get high powered charging, but at least they are inexpensive and you can get them at Amazon, CSquid cables.

It is not a trivial task to design an inexpensive 2 amp USB charger. I have designed one, but it is expensive to make in small quantities. I don't advertise them anymore, but you can see them here: www.commitlift.com/usbchargers.html I made a couple of them for my son's RV-7 and can even supply them mounted in standard sized panel cutouts. The advantage of these is that they attach to your panel with two screws and use heavy duty USB port hardware, which is one reason they are expensive. The other reason is the circuit that converts 12 volts to 5 volts efficiently, is not a trivial and inexpensive device. If you are interested PM me.
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  #12  
Old 06-13-2012, 02:57 PM
N1593Y N1593Y is offline
 
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Location: Sisters, OR
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Quote:
Originally Posted by YellerDaisy View Post
Hi Bill,

Could you share where you found the above (single port USB adapter)? I've been looking for that very thing and have only been finding board mount type connectors. Was about to resign myself to installing a standard cigarette lighter plug and using a USB adapter.

Thx!
Amazon.com has a bunch of them. Make sure you know how much current you need and realize you may also have to get a cheater cable if you are trying to charge a tablet that need more than 1/2 amp.
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  #13  
Old 06-14-2012, 06:20 AM
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bill@fusion4.net bill@fusion4.net is offline
 
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Location: Suwanee, GA
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Quote:
Originally Posted by N1593Y View Post
It is not a trivial task to design an inexpensive 2 amp USB charger. I have designed one, but it is expensive to make in small quantities. I don't advertise them anymore, but you can see them here: www.commitlift.com/usbchargers.html I made a couple of them for my son's RV-7 and can even supply them mounted in standard sized panel cutouts. The advantage of these is that they attach to your panel with two screws and use heavy duty USB port hardware, which is one reason they are expensive. The other reason is the circuit that converts 12 volts to 5 volts efficiently, is not a trivial and inexpensive device. If you are interested PM me.
That is exactly what I have been searching everywhere for. At $50 that is more than mass produced electronics, but not bad for aviation equipment. It will make a much cleaner install then anything else I had found.


I think if you did a little search engine optimization you might sell a lot of these. (Ordered 1 for now, might order a couple more).
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  #14  
Old 06-26-2012, 08:36 PM
Dalmech Dalmech is offline
 
Join Date: May 2012
Location: Atlanta
Posts: 38
Default What say you EE's

Would a buck converter work? Ebay selling them cheap.

http://www.ebay.com/sch/i.html?_nkw=...rter&_osacat=0.
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  #15  
Old 06-26-2012, 08:38 PM
Dalmech Dalmech is offline
 
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Location: Atlanta
Posts: 38
Default Better Link

http://www.ebay.com/itm/DC-12V-22V-t...item3f18326957
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  #16  
Old 06-26-2012, 08:56 PM
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mannanj mannanj is offline
 
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Location: Mtns of N.E. Georgia
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Quote:
Originally Posted by Dalmech View Post
Would a buck converter work? Ebay selling them cheap.

http://www.ebay.com/sch/i.html?_nkw=...rter&_osacat=0.
Check the output voltage. Shows 9V DC. The Ipad usb needs 5V DC.
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  #17  
Old 06-27-2012, 05:53 AM
Dalmech Dalmech is offline
 
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Location: Atlanta
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I mistakenly grabbed a link to a 9 Vdc but the buck converters come in many flavors including 5 Vdc.
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  #18  
Old 06-27-2012, 07:21 AM
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airguy airguy is online now
 
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7805 and a Darlington, plus a couple miscellaneous pieces and half an hour for assembly.
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Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.
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  #19  
Old 06-27-2012, 07:05 PM
BobTurner BobTurner is offline
 
Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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Greg, I don't think it's quite that easy. Your control voltage needs to be more like 6.2 volts (for the 0.6 volt drops across the base-emitter junctions) but the real issue is the 16 Watts (2 amps * (13-5) volts) of power you'll be dissipating. I think you'll need a good heat sink and maybe forced cooling air.
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  #20  
Old 06-27-2012, 09:14 PM
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craigvince craigvince is offline
 
Join Date: Sep 2006
Location: Stockton, CA
Posts: 1,207
Lightbulb

I just purchased two of these for $19.95 each.
http://www.amazon.com/gp/product/B00...fatcityfour-20



I cut the cig plug off and hard-wired it to a 5a CB, mounted one under the panel and one behind the seat in the baggage area.
Very handy!!
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