diy usb port for my car from an old wall charger

Reply

  #1  
Old 10-04-13, 11:00 AM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
diy usb port for my car from an old wall charger

I had an old usb wall charger. I took the thing apart and put the board into my car's dash. when I feed it power from the same line that feeds the cigarette lighter the red LED on it glows but my phones wont charge. I tested the usb out put and I am gegting 5v through pin1. and also when I plug my phone the led dimms down a bit. any idea why it isnt charging my phones? is it because the thing was made for wall usage (220v not 12v)?
 
Sponsored Links
  #2  
Old 10-04-13, 11:16 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 17,964
USB is a loosely defined specification and there is no one USB. Some devices, even though they use a USB plug, have different pin outs and may not be interchangeable. What I call the "I" style is often used by Apple devices while "S" is used by others like Samsung. The plugs look the same but are different.

I don't know how your old wall charger is made but it was designed to accept AC current probably between 100 and 240 volts. It may not be made to accept 12 volt DC as an input.
 
  #3  
Old 10-04-13, 11:28 AM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
yes, its made for 110 to 240v input. but it still outputs 5v through usb when connected to the 12v dc. could the problem be not related to voltages at all? might it be related to low current?
 
  #4  
Old 10-04-13, 01:23 PM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 17,964
What type phone do you have and what brand was the charger? Is your phone an iPhone?

As I mentioned it may simply be the wrong USB. A Samsung or other brand USB charger will often not work if you plug a iPhone or iPad's USB cord into it and vice versa. The plug and socket look the same and they can be plugged in and still not work. Very annoying.

I have a Anker battery pack that I use to charge devices when I'm out in the woods. It has two USB ports on the side. They look the same but are wired different. One works with Apple devices and will charge my iPod. If I plug my Casio cell phone into the "Apple" port it will not work and if I plug my iPod into the other port it will not work.
 
  #5  
Old 10-04-13, 04:03 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,597
I'm actually surprised you got anything at all out of that charger.
You need to locate a 12vdc to 5vdc adapter.

The convenience store here sells a plug in cigarette lighter plug with a USB charge port built right in. They're $2.00 USD.

Name:  usb-car-charger.jpg
Views: 11651
Size:  16.4 KB
 
  #6  
Old 10-04-13, 10:35 PM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
I actually thought of that first. Buying the usb cigarette lighter charger and putting it behind my dash. Only problem is those things go for around $20.00 (USD) where I live (Ethiopia).

@Pilot Dane,
What if I take out a USB port from an old PC? Those things charge any phone that I plug into them. My old Dell Optiplex 270 has these two USB ports at the front, and I am thinking of taking it out using it.
 
  #7  
Old 10-04-13, 11:00 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,597
No....won't work. The USB jack is just a connector. The 5 volts is generated elsewhere on the board.
 
  #8  
Old 10-04-13, 11:25 PM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
Ok, is it possible to follow the wires and get to where the 5v is generated or is it inside the power supply?

And i attached the board of the wall charger i was talking about earlier.Name:  image.jpg
Views: 3997
Size:  52.7 KB
 
  #9  
Old 10-05-13, 05:45 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 17,964
Did your phone charge from that USB adapter before you modified it?

Here is an excerpt I found that might explain one problem charging via USB.

Many phones and devices, especially if they are more than two or three years old, use the USB data link to check with the charger or PC to make sure it is capable of supplying the necessary current. However, most plug-in chargers are ‘dumb’ and have no means of communicating with the phone, so it plays safe and charging is disabled. The USB specification was updated in 2007 and many recent phones now have a built in test circuit that automatically checks the charger current to see if it is sufficient, before allowing charging to begin.
 
  #10  
Old 10-05-13, 05:59 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,597
Either take a close up pic of the parts side and/or post all the numbers on that part.

Name:  image.jpg
Views: 3015
Size:  18.6 KB
 
  #11  
Old 10-05-13, 09:23 AM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
Camera has trouble focusing on it, its not that much visible even to the naked eye. I think this is what written on it:

008T
Q 817C

The first part might be an O and not zero, I cant really tell. And by the way, what is that?
 
  #12  
Old 10-05-13, 10:36 AM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
@Pilot Dane, that was a great read. It explains why many cheap wall chargers won't charge an iPhone. But there are still a lot of home made chargers that will charge an iPhone and through a bit googling I came across ideas that say that I need to run 2.5v through the data pins. Is this true, will this work?

And about the wall charger, no it didn't charge the my iPhone before any modifications. That was because no power was coming through any of the pins. I just re-soldered the pins and then I was getting 5v through pin1. But I didn't try it after that, I just figured it will work and put the thing in my car.
 
  #13  
Old 10-05-13, 07:25 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,597
I had hoped that part was a small 3 pin 5v power regulator IC. The numbers you left don't help me much. Could be a private branded part.
 
  #14  
Old 10-05-13, 11:47 PM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
Ok, I just need to ask one final question. Reading from a lot of DIY tutorials I know that I need some kind of 5v regulator, and they all say its easy to get from shops but thats not the case for me. You cant easily find them.

So my big question here is what kinds of electronics might have this 5v regulator in them? A friend of min owns this repair shop for TVs, DVD players and so on.

Sorry if I went off topic.
 
  #15  
Old 10-06-13, 05:09 AM
Member
Join Date: Oct 2012
Location: USA
Posts: 614
The wall charger has circuits to rectify AC to DC as well as step down the voltage to 5V. In your case, it's probably just a matter of reducing the 12V to 5V which I suppose you could do with resistors of the proper value (you do the math). The car chargers probably use a more sophisticated voltage regulator built into a single chip.
 
  #16  
Old 10-06-13, 12:08 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 45,597
The following are generic part numbers. There are more with private part numbers.
If your friend runs a repair shop he'll know what uses those regulators.

7805 +5v 100ma.
LM123 +5v 3a
78L05 +5v 100ma.
There are 3 pin devices. The 100ma.versions look like the part I had an arrow pointing to.
 
  #17  
Old 10-07-13, 02:11 AM
Member
Thread Starter
Join Date: Feb 2013
Posts: 9
Ok, after a bit of looking around at my house I found this: an MP3 FM Transmitter with a USB port.

Attachment 50972

As you can see it has a KA78M05R 3-terminal 0.5A positive voltage regulator (yay!!). I tested the transmitter as a transmitter and it works great. It plays music both through USB thumb drives or memory cards. So I gave it a shot and connected my iPhone to it (for the purpose of charging only) and a weird thing happens. The iPhone charges one second, it doesn't the next second, then it does charge again and then not charging on and on. This happens very quickly and the the beep/vibration that comes when you plug the phone to charge ports comes on and off like crazy. I didn't panic, I tested my brothers Galaxy S, same thing except it charges for a longer seconds before it stops charging for a few another seconds and back to charging and so on. I simply can't tell why this is happening. Plus both phones think they are connected to a PC.

I liked the transmitter as a transmitter since my cars stereo is an old Kenwood DPX90 and it has no AUX port nor USB inputs. And I also wanted to modify it so that I could charge my phone too while still listening music.

Any possible way of achieving this?
 
Attached Images  
  #18  
Old 10-07-13, 06:46 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 17,964
Here (The link has a lot of photos.) is a article comparing iPhone chargers and what goes into them. Apple goes to a lot of trouble to filter the power fed to their devices. I don't know if it's required or just a "nice to have" feature but I would include some filtering in your charger circuit.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes