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How to build a basic power regulator circuit?

Discussion in 'Electronic Basics' started by SoundMate, Apr 16, 2009.

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  1. SoundMate

    SoundMate Guest

    I'm pretty new to electronics and I want to learn some more by
    building a basic power regulator so that I can power/charge a USB
    enabled device (e.g my mobile phone) from a battery pack that I have
    which puts out around 7V/1.6A. I've gathered that a regulator IC will
    do most of the work but I've no idea about how to make up the rest of
    the circuit. Can anyone point me to further reading on making a
    customised power regulator?
     
  2. Tom Biasi

    Tom Biasi Guest

    Why don't you first type this in google: "build a battery powered usb device
    charger"
    Tom
     
  3. Nobody

    Nobody Guest

    One issue with USB power is that USB devices are limited to 100mA unless
    they request more (in which case, they may get up to 500mA), and to 500uA
    when suspended (which occurs when the bus is idle for 3ms). Depending upon
    the device, the supply may need to be able speak USB in order to get the
    device to draw power. And getting something to speak USB isn't a
    begginer's project.

    OTOH, if you just need to supply 5V, it couldn't be simpler. The circuit
    need be nothing more than a 3-terminal regulator, e.g. 7805.

    [The 7805 needs 2V dropout, so your input would need to be at least 7V.
    Use a low-dropout part (e.g. LM1117) if the battery voltage is likely
    to dip below that.]

    If either the input or output leads are long, it's worth adding a 10uF
    capacitor on that side of the regulator.
     
  4. Nobody

    Nobody Guest

    Most of the links on the first page refer to boost converters, which
    aren't suitable if the battery voltage is greater than 5V.
     
  5. SoundMate

    SoundMate Guest

    I did, and this is a great way of doing it if - you're using the same
    battery as in the examples sourced through google and/or you have a
    clue what you're doing, which I clearly do not.

    Thanks for the comments everyone, I'm getting a step closer now.
     
  6. SoundMate

    SoundMate Guest

    It seems that the wall charger for the phone outputs at 500mA so I
    think a MC78M05CT is looking good unless I am mistaken. This is the
    most readily available for me and it puts out at the ratings I need.
    Thanks again for your advice.
     
  7. Tom Biasi

    Tom Biasi Guest

    So look at some other pages.
    Tom
     
  8. SoundMate

    SoundMate Guest

    Do you always bring so much to the table?
     
  9. Tom Biasi

    Tom Biasi Guest

    I suppose you just want someone to do your research for you.
    If you had indicated what you have done so far and where you were having
    trouble understanding maybe I could help.
    You asked to be pointed to further reading and I did that.

    Tom
     
  10. SoundMate

    SoundMate Guest

    No you didn't, you were just being crude, and you still are. As the
    poster prior to you illustrated, I had stated what I was looking for,
    in that I did not know how to equate for the particular variable
    (cell) I am using. I know that I need to learn more, I therefore don't
    need someone like you to tell me this in mankinds most banal form.
     
  11. Tom Biasi

    Tom Biasi Guest

    Sorry that you were offended. I had no intentions other than to point you to
    some research..
    Tom
     
  12. Rich Grise

    Rich Grise Guest

    You know, there's more to google than a portal into USENET.

    Try the "search" side of google; search on, say, "power regulator circuit"
    Try it with and without quotes.

    Good Luck!
    Rich
     
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