Fitting mini A USB plug

  bumpkin 16:25 01 Feb 13

Hi, I want to change the type A USB connector on a tablet external keyboard to to a mini type A. I was using an adapter which was fine but thought I would be clever and just solder the wires together and use a bit of shrink sleeve as it would be neater. The wires coming out of the keyboard were incredible small compared to even the thinnest ones I have seen and a different colour to normal. As a temporary measure I soldered on some slightly thicker ones so that I could try and find the correct combination by twisting them onto the wires to the connecter on a trial and error basis. The wires from the keyboard are Red Black Green Blue. Tried everything I can think of unless there is more to it than I thought. Can anyone advise please.

  Chronos the 2nd 16:37 01 Feb 13

Is this any help?

Micro USB Pinout.

Standard USB Pinout.

  bumpkin 17:13 01 Feb 13

Thanks Chronos, I did check this before I started but the cable out from keyboard has a blue wire, no white one. I connected the blue from keyboard to white on the plug as it seemed logical but it did not work. I have checked the output from the tablet and red and black are the 5v so I assume the other 2 are data but can't get it working. Voltage is right polarity and I have tried reversing the other 2 which I am assuming are data or could the blue one be ground. Just don't know, I thought this would be an easy little job.

  Chronos the 2nd 18:37 01 Feb 13

USB Universal Serial Bus Cable

Pin# Label Function Standard Wire Color

1 +5 Volts Power Red

2 Data - Signal - White

3 Date + Signal + Green

4 Ground Ground Black

Perhaps as you say blue is ground?

  Bris 18:42 01 Feb 13

[is this any help? ]1

  bumpkin 23:14 01 Feb 13

Thanks, all suggestions are helpful on this one. A could buy a new keyboard/case for about a tenner but it will still have the standard USB outlet so back to square one. I kept telling myself not to bugger about with it but could not resist it in the end. Now I would like to resolve it anyway as a learning experience. Some more info, the wires coming out of the keyboard are red, blue, green and a plain copper or gold looking one which I original thought was black as I had not properly remove the outer insulation not having an electron microscope handy. The colour coating on the fine wires is not plastic, seems like some kind of spray on coating. Tested it with a meter and it is an insulator of some kind, too thin to remove normally, had to burn it and it ignites quickly for about a second, then have access to the core wire. If I plug a usb mini x usb standard adapter into the pc I get 5V reading on the black and red as one would expect. If I plug a mini connector directly into the pc a cannot find a 5V output at all. Sorry to ramble on but I cant be the first person daft enough to try this, someone must know the answer :-(

  Bris 12:39 02 Feb 13

There is a lot of information in this link especially the links on the right which although relating to mobile phones may give some clues to the problem.

I note that with mini USB that there are 5 pins one of which can have a special function of cable detection, as I read this it means that this pin indicates to the receiver whether a device is connected or not and maybe if its not providing the correct signal then the receiving device will not turn on the 5 volt feed. As far as I know there should always be 5 volts on the two outside pins so either the socket is faulty, the plug is faulty or the above applies.

The copper wire you mentioned appears to have an insulating coating as found on wire used in transformers.

click here

Good luck with it.

  bumpkin 15:19 02 Feb 13

Hi Bris, thanks for your reply. Having spent some time on this I have found that the connections (pinouts) from the plug that I cut off to the keyboard are pin1 green=ground, 2 blue=data-, 3red=data+, 4orange=5V+. I have never encountered this combination before. I think you are right about the extra pin on the mini connector firing up the voltage but I had nowhere to connect it other than ground. As the adapter delivers 5v I think the connection is made inside via a small resistor. Even putting it back as it was would not work, half the problem was trying to solder such tiny wires. I how now given up and ordered a new keyboard/case. I did learn something though, not to do it again :-)

  woodchip 18:05 02 Feb 13

5 volts on one of the wires, connected wrong will blow something

  bumpkin 22:23 02 Feb 13

Good point woodchip but have you or anyone else seen that pinout configuration before. I probably did put voltage up the wrong wire but hardly surprising as I cut off a standard USB plug and assumed standard wiring. No serious damage luckily, just another tenner up the swanee :-)

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