Solar cell phone charger problem

Thread Starter

Michael.Riley

Joined Jan 3, 2015
15
I have built a small solar panel, 12V no load output, 1.4 A short circuit current out put. I also built a switching voltage regulator based on an LM317 adjustable regulator. I bought a USB connector at Radio Shack (voltage only), but when I try to charge my cell phone or my Kindle, neither one indicates that it is taking a charge. I have checked that the voltage at the USB pins is 5V, and checked that I have the correct pin polarity ( At least, it is the same as my wall wart chargers.) I have checked the output voltage of the regulator while connected to the devices, and the drop in voltage is .01 V. I have no trouble running a couple of small fans (.18 and .16 amps) and a small LED flasher at the same time (I adjust the voltage output up for these 12V items). Any ideas would be welcome.
 

MikeML

Joined Oct 2, 2009
5,444
Most devices accepting charge look at the data pins to validate that charger is legit. If your data pins are unconnected, chances are your cell phone and Kindle just ignore the presence of the 5V because you are not tricking them into thinking that your charger is real...

Apple started playing this stupid game to force people to buy Genuine Apple chargers.
 

Thread Starter

Michael.Riley

Joined Jan 3, 2015
15
Post a schematic, it will help out figuring out what is the problem.
I'll post a schematic as soon as I figure out how to convert a Diptrace *.dch file to something that I can send. However, the schematic is based on the following: http://www.circuitstoday.com/3a-switching-regulator, with a few minor changes, to wit:
Q1 is a TIP42G 6A transistor; D1 is a Schottky dual, common cathode 15A; R1 is 4 1 ohm resistors in parallel; and L1 is an unknown value inductor, fairly large.
Does that help?
 
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Thread Starter

Michael.Riley

Joined Jan 3, 2015
15
Most devices accepting charge look at the data pins to validate that charger is legit. If your data pins are unconnected, chances are your cell phone and Kindle just ignore the presence of the 5V because you are not tricking them into thinking that your charger is real...

Apple started playing this stupid game to force people to buy Genuine Apple chargers.
I have a wall wart that appears to have only two pins, producing 850mA at 5V, that charges both my devices without an issue. I did manage to get the Kindle to show a charging symbol by jacking the output voltage up to about 8.5 volts and then turning the voltage back down to 5.5V, but it didn't actually charge it.
 

bushrat

Joined Nov 29, 2014
209
I did manage to get the Kindle to show a charging symbol by jacking the output voltage up to about 8.5 volts and then turning the voltage back down to 5.5V, but it didn't actually charge it.
Umm... just because you can, doesn't mean you should..
upload_2015-2-28_16-15-12.png
It works in simulation, and the only thing that I can think of is what MikeML said about apple chargers.
 
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djsfantasi

Joined Apr 11, 2010
9,155
image.jpg Here's a schematic from the web that I refer to. It shows how to apply the proper voltages to the data pins, using voltage dividers. It's specifically for an iPhone.
 

tindel

Joined Sep 16, 2012
936
Per the USB Battery Charging Specification, section 1.4.7 - Dedicated charging ports shall short the D+ and D- lines. Iphones are 'special' and do not conform to the USB spec, that I'm aware of anyway.


1.4.7 Dedicated Charging Port

A Dedicated Chargin Port (DCP) is a downstream port on a device that outputs power through a USB connector, but is not capable of enumerating a downstream device. A DCP shall source IDCP at an average voltage of VCHG.

A DCP shall short the D+ and D- line
 

Thread Starter

Michael.Riley

Joined Jan 3, 2015
15
Per the USB Battery Charging Specification, section 1.4.7 - Dedicated charging ports shall short the D+ and D- lines. Iphones are 'special' and do not conform to the USB spec, that I'm aware of anyway.
Thanks. That info may do it. Do you know if that is short to each other, or short to ground?
 
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Thread Starter

Michael.Riley

Joined Jan 3, 2015
15
Thanks a lot, to everyone who responded. I took apart a dead USB wall wart to use the USB socket, found that the data pins were simply soldered to each other, and I went with that. Both my Kindle and cell phone now charge immediately through my regulator, supplied by a 12V power supply (A Heathkit ET 3200, believe it or not). When the sun comes out tomorrow I'll try my solar panel, but I'm sure it will work. Many thanks, again, to everyone.
 
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