first of all please sorry if my question would sound dumb, I'm new to electrical engineering I've did my first soldering of two wires just yesterday. So here goes the question: I have 5V 60A LED DC power supply (also I have lab. i.e. variable voltage dc power supply which I use for testing things).

I'd like to adapt my 5V 60A power supply to a general purpose USB charger station with multiple USB docks, I have several female USB wires. And I guess that making a USB charger out of 5V supply is something more than just soldering plus to plus (red to red wire) and minus to minus (black to black), which I already did and it didn't worked.

What has to be done in order to make a USB charger out of 5V power supply and a female USB cable.

Thank you in advance

  • \$\begingroup\$ What kind of phone \$\endgroup\$
    – Passerby
    Commented Jul 14, 2015 at 23:33
  • \$\begingroup\$ I use IPhone for testing but planning to use Raspberry Pi 2 for regular purpose, on IPhone I've found this great article which I think should resolve the problem with IPhone learn.adafruit.com/minty-boost/process \$\endgroup\$
    – Lu4
    Commented Jul 14, 2015 at 23:44
  • \$\begingroup\$ The PI will work straight off the 5v. The iPhone requires handshaking, as the Adafruit article explains. There is also the USB Charger standard, which uses a different setup than Apple on the D+ and D- pins. \$\endgroup\$
    – Passerby
    Commented Jul 14, 2015 at 23:54
  • 1
    \$\begingroup\$ Ok, so for PI purposes I don't need all this resistor stuff, that's nice... \$\endgroup\$
    – Lu4
    Commented Jul 15, 2015 at 0:22

1 Answer 1


There is nothing more than just soldering 5V(+) to 5V(+) and GND(-) to GND(-) .

USB uses also 5V so there is no need for any aditional circuitry.

The only thing you may want to do (which isnt necessary) is to use pullup or pulldown resistors on the data lines because many smartphones uses this to detect how much current they can draw from the power adapter.

Using pullup or pulldown resistors means that you connect a resistor from 5V(+) or GND(-) to one of the data pins (Usually they are white and green when you use an old USB Cable). But you would need to search online for the resistor value. But that is not necessary, just optional

  • \$\begingroup\$ It seems that I was attaching GND to Minus that's probably why it wasn't working.... \$\endgroup\$
    – Lu4
    Commented Jul 14, 2015 at 23:12
  • \$\begingroup\$ No thats ok. GND means Ground and is equivalent to Minus \$\endgroup\$ Commented Jul 14, 2015 at 23:16
  • \$\begingroup\$ In my lab. power supply I have + (plus) - (minus) and GND (guess it's ground) well if I stick plus to plus and minus to ground GND it won't even light up my digital USB V/A meter. But it works with minus, but still I'm unable to charge for example the phone, I see it draws 0.01A so I guess it's related to what you have said about resistor on the data line, so originally the problem was related to this resistor rather than USB design... Thank you in any case... \$\endgroup\$
    – Lu4
    Commented Jul 14, 2015 at 23:29

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