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B Battery Operated Cell Phone Charger

  1. Apr 27, 2016 #1
    Hey guys,

    I am building my own battery operated cell phone charger. I am pretty sure I built my circuit correctly because the outputs I am reading on my USB output port: pin 1 is 5V and on pin 4 is 0V... which are good readings (and tells me that my voltage regulator is functioning properly and that my ground is connected properly).

    When I plug my 'micro USB' chord into my charger to charge my phone, nothing happens.

    Any ideas?

    I used two different DMMs to check the voltage on the pins in the USB port. Again I am reading 5V on pin 1 and 0V on pin 4. I have tried several different micro USB chords as well. For some reason, my cell phone will not charge off of this.

    I have two ideas as to what may be happening...
    1. due to the way I hot glue gunned the USB port to the container my circuit is in, there glue may be insulating the voltage from entering my micro USB cable when I plug it in (or the glue is affecting this in some manner)
    2. The last i checked this was not true, but just in case.... I am not using Pins 2 or 3 (the data pins on the USB) at all because to my knowledge, droids just need 5v on pin 1 and 0v on pin 4 to charge (as opposed to apple devices that requires a data signal in order to charge). Is this the same for droids now too? do you think I have to wire the data pins in?

    Any ideas will be a huge help. I am stumped.
  2. jcsd
  3. Apr 27, 2016 #2


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    Gold Member

    Have you tried loading the charger output with something other than the cell phone and/or measuring the output under load (cell phone or other) ?

    The big thing is to measure the output under load. Measuring it unloaded is worth doing, but not as significant as the loaded value.
  4. Apr 27, 2016 #3
    AFAIK current Androids with USB 2.0 still require only +5V to charge (I have a two-leaded charger and modern phones still charge), the data signal is only needed when you plug it to a computer and the phone shows a message to mount the internal storage/SD card/charge only
    Did you measure the USB voltage with the phone plugged in as Phinds stated? Most likely it could drop depending of the maximum power delivered by the circuit and the battery size of your phone (bigger batteries as well as more powerful phones need more amperage, thus power).

    Watch the USB OTG pin in your USB lead to avoid entering into OTG mode.

    What phone are you using?
    What battery and regulator are you using in your charger?
    Last edited: Apr 27, 2016
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