Connect with us

USB 5V power from 12V car supply

Discussion in 'General Electronics Discussion' started by john2k, Jun 16, 2015.

Scroll to continue with content
  1. john2k

    john2k

    183
    3
    Jun 13, 2012
    I have a 12v to 5v(3A Max) converter. I'm planning to hook this to charge my Nexus Android tablet as part of a car in-dash install. My question is: The converter seems to be regulated in terms of voltage but the current says 3A max. Therefore there doesn't seem to be any form of current regulation. Does that mean the tablet will only draw what it needs to charge and the device will only give 3A max? What are the chances of too much current being delivered to the tablet?

    Thanks
     
  2. Martaine2005

    Martaine2005

    2,968
    817
    May 12, 2015
    Hi John2k,
    Your assumptions are correct..
    The Max is 3a.
    Your tablet will only draw the current it needs.
    You could use a 5v 5a and the same applies. A device will only draw what is required.
    Martin
     
    hevans1944 likes this.
  3. john2k

    john2k

    183
    3
    Jun 13, 2012
    Thanks Martaine2005
     
  4. AnalogKid

    AnalogKid

    2,414
    686
    Jun 10, 2015
    All true, but an inline fuse would be prudent.

    ak
     
    hevans1944 likes this.
  5. john2k

    john2k

    183
    3
    Jun 13, 2012
    So if converter is rated at 3A max, should I put a 5A fuse or a 3A fuse?
     
  6. Martaine2005

    Martaine2005

    2,968
    817
    May 12, 2015
    Your 12v to 3v adapter probably has a 1a fast blow fuse.
    Mine has a 1.6a 250v fast blow fuse. Don't worry about 250v, it's just a maximum voltage.
    It should be located in the 12v end of the adapter like this picture. Where the spring is..

    charger.jpg
     
    hevans1944 likes this.
  7. john2k

    john2k

    183
    3
    Jun 13, 2012
    The 12v to 5v converter i'm looking at is like this: not sure if it will have a fuse inside that housing. So considering maybe to add an inline blade fuse maybe on the red wire. Is that ok? and what amp fuse would be recommended?

    [​IMG]
     
  8. Martaine2005

    Martaine2005

    2,968
    817
    May 12, 2015
    Amps = Watts / Volts
    15w / 12v = 1.25amps
    I doubt if your tablet will even draw an amp. The fuse should be the 'weakest' link to protect the device.
     
    hevans1944 and john2k like this.
  9. john2k

    john2k

    183
    3
    Jun 13, 2012
    So a 1A mini blade fuse should do the trick?
     
  10. Martaine2005

    Martaine2005

    2,968
    817
    May 12, 2015
    Yes. But a fast blow fuse.
    Martin
     
    hevans1944 likes this.
  11. john2k

    john2k

    183
    3
    Jun 13, 2012
    Do they sell fast blow fuses in blade format? I think they just in the glass style. Should I just put an inline glass 1A fast-blow fuse then instead of blade fuse?

    Many thanks
     
  12. Martaine2005

    Martaine2005

    2,968
    817
    May 12, 2015
    Without searching the internet, I have no idea.
    I don't see any reason why they would not sell them..
    But if not, a glass inline would be perfect too.
    Martin.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-