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5V to 4.3V PSU

Discussion in 'Power Electronics' started by IMtheS, Mar 7, 2015.

  1. IMtheS

    IMtheS

    5
    0
    Mar 7, 2015
    Hello, I'm new here and i'm not very expirienced in electronics.

    I bought a beard trimmer in ireland, it came with this funny plug:

    [​IMG]
    4.3V output max 70mA

    I thought instead of using a plug converter im my home country i maybe could build a little power converter on my own, since i have som resistors laying around at home and use USB to charge it up.

    I came up with this little scheme:
    [​IMG]


    I actually don't know the battery's resistance, it's just guessed using ohms law (5V÷70mA=61Ohm).

    Do you think this would work to charge up the trimmer without breaking it?
     
  2. davenn

    davenn Moderator

    13,329
    1,769
    Sep 5, 2009
    Hi there
    welcome to the forums :)

    your images are too small and unreadable

    show us something a bit bigger
     
  3. duke37

    duke37

    5,253
    726
    Jan 9, 2011
    There are a lot of funny plugs here, its hilarious. :)
    It is not just a plug, it is a power supply.

    You could get a 5V supply and place a silicon diode in series with it to drop 0.7V and get 4.3V.
     
    IMtheS likes this.
  4. IMtheS

    IMtheS

    5
    0
    Mar 7, 2015
    Thank you!
    Sorry, here is the full resolution:
    http://s14.postimg.org/4x4js8zgx/Screenshot_2015_03_07_14_20_24.png

    Of course! I think i have some diodes laying around. I haven't thought of diodes! Thank you, i think this is the easyiest solution. So i need just a usb plug and a diode and i don't have to solder resistors in parallel to get wierd restistances.

    Cheers, dimitri
     
    Last edited: Mar 7, 2015
  5. duke37

    duke37

    5,253
    726
    Jan 9, 2011
    CPC which is part of Farnell sell in the UK adaptors for many mains standards. Presumably you can get them in Canada also.
     
  6. Gryd3

    Gryd3

    4,098
    875
    Jun 25, 2014
    Duke's post #3 is ideal. Your drawing uses a voltage divider which will not be stable.
    Voltage dividers are almost always frowned upon when they are used to provide power, they are typically only ever used in signalling only. (Say, to convert a 5V signal to a 3.3V signal.)

    The Diode simply gets placed in series with the 5V power supply.
     
  7. Jakub

    Jakub

    4
    0
    May 1, 2015
    Hello,

    I have the same problem. I bought beard trimmer Philips QG3322, and I would use it for traveling with my laptop and solar panel, sometimes. So I rather prefer charge it by USB. I thought first, that I can easily change NiMH battery in trimeer (which I can charge with my battery charger), but it was my mistake. I still have chance to return it to the shop, but I like it. It´s simple beard trimmer with good quality, I hope:-]

    I´m electro amateur, so if somebody can help with information how can I build USB charger, or build it for me for some good price, I will be very happy:-]

    Thank You very much for Your answer and I´m sorry for my english:-]

    (I will stay in UK till October, I´m originally from Czech Republic.)
     
  8. IMtheS

    IMtheS

    5
    0
    Mar 7, 2015
  9. Jakub

    Jakub

    4
    0
    May 1, 2015
    Hello, and Thank You for Your answer.

    I tried to wait for your experience with Mini MP2307DN, and then I will see. I still have time to do it and few more things what I would order from dx.com (for cheaper delivery fee).

    So, please let me know, Than You.

    Jakub
     
  10. Arouse1973

    Arouse1973 Adam

    5,164
    1,078
    Dec 18, 2013
    Is the power supply DC or AC?
    Adam
     
  11. Jakub

    Jakub

    4
    0
    May 1, 2015
    Hello,

    I write for you what is on Adaptor:
    AC/DC - Adaptor
    Input: 100-240V, 50-60Hz 2W
    Output: 4.3V - 70mA


    Than You, Jakub
     
  12. Jakub

    Jakub

    4
    0
    May 1, 2015
    Hello IMtheS,

    do you have any news about the usb charger for beard trimmer.

    Thank You, Jakub
     
  13. IMtheS

    IMtheS

    5
    0
    Mar 7, 2015
    I fried it..
     
  14. ver chan

    ver chan

    55
    1
    Jun 27, 2015
    plug is not a serious problem, you can cut it out and replace by a convenient one, speaking of batteries, batteries is not a resistor to have a constant and certain resistance,,, you can use voltage regulator IC to have fixed volatge output at different value LM 78____ series, look at alldatasheet.com for refference
     
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