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Current regulator

Discussion in 'Electronic Basics' started by nescafe, Sep 15, 2012.

  1. nescafe

    nescafe Guest

    Hi.
    I need to create some kind of charger.
    The "charger" will be powered from dc source ( 1,5 AA battery ).

    The voltage should stay the same but the current should be regulated
    like this:
    - charge time: 1 day --> 1,5 / 50mA
    - charge time: 2 hours --> 1,5 / 100mA
    - charge time: 4 hours --> 1,5 / 200mA
    - charge time: 4 hours --> 1,5 / 500mA
    - charge time: 7 hours --> 1,5 / 1A
    --------------------------------------------
    For now i will switch the charge with some micro switch but in future
    this should be done with ne555 timer.
    Is there any schematics how to make this pcb ?

    One input, with multiple regulated current outputs, controlled per micro
    switch.

    Thnx in advance
     
  2. nescafe

    nescafe Guest

     
  3. Assuming the load is a battery, that is, something whose internal
    chemistry you have no control over, you can control the voltage, or
    the current, but not both.
    (I think the guy's name was Georg Ohm)
     
  4. Jamie

    Jamie Guest

    You would need to use the CMOS version of the 555 timer to operate at
    that low of voltage.

    Using a buck boost switch you can generate higher voltages at lower
    currents, great for charging I guess.

    Unless I miss understood your posting, I assume you're using a single
    cell as your DC source ? Or do you mean you want to charge a single cell
    from some other DC source?

    Jamie
     
  5. Jamie

    Jamie Guest

     
  6. Phil Allison

    Phil Allison Guest

    "nescafe"

    ** Better use two ( in series) - cos using just one is never gonna work.

    The voltage of a 1.5V cell drops steadily during discharge.



    .... Phil
     
  7. nescafe

    nescafe Guest

    One homemade cell can be charged up to 1A (max) and standard voltage is
    around 0.75
    But to get to this 1A i have to charge the cell on the way i described
    before.
     
  8. Jasen Betts

    Jasen Betts Guest

    555 is too fast. try CD4060
    you won't get 7 hours at 1A from an AA
     
  9. Jamie

    Jamie Guest

    +---------------+-----++
    | 2N3904 | |
    12 Volt in | ___ |/ |
    +-+-------+-+|___|--+--+| |
    + | |> +
    - 4.7K | + |/ 2N3055
    --- | +--+-|
    | | |> 0.25 Ohm
    +--------++ | ___ Cell Load
    GND | | +---+--+-|___|-+-------+
    + | | | |
    V | | .-. |
    - + U1 | | |<--+--+
    | | 470k /|| | | 10k POT
    1N914 Types V \| ___ /+|+ '-' Current Limit
    - 2N3904|--|___|--< | |
    | <| \-|+---------+|
    V | \| .-.
    - + LM741 | |
    | | Or like it | | 220k
    | | '-'
    === === |
    GND GND ===
    GND


    U1 Vee (-) = GND
    U1 VCC(+)= 12V
    (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

    That is a voltage limited adjustable current 0..1 amp.
    The Max output voltage should be around 1 volt.

    As for the timer, in your case, why not use one of those wind up
    mechanical timers that has a switch on it? You can get them to extend
    to a lot of hours. You find them on car battery chargers etc..

    I tried to do that all with transistors, but it was getting messy..
    Too many parts. So I through in the OP-AMP as the current sense.

    Jamie
     
  10. Jamie

    Jamie Guest

    Where is the voltage limiting control? That is needed since he is
    only looking for charge around 0.75 volts, unless he made some mistake
    or I did?

    I don't know exactly what he is doing , but as cell charge
    comes up the current usually drops back, in this circuit here, the
    voltage is just going to raise and raise.

    The one I showed only goes up to ~ 1.0 Volt.

    Did I missed something ?

    Jamie
     
  11. nescafe

    nescafe Guest

     
  12. Jamie

    Jamie Guest

    that's fine, I'll stick with limiting the voltage.

    As a cell increases with voltage, the current drops back. if you are
    attempting to maintain current, the voltage will just keep raising until
    at some point, the cell could get damaged. A little over is fine, which
    is needed, but really, using 12 volt source to charge a .75 volt cell?

    Oh, so much for that. I hope you don't get into the charging business.


    Jamie
     
  13. Jamie

    Jamie Guest

    Good luck. Wouldn't of been my choice.

    Jamie
     
  14. Jamie

    Jamie Guest

    Nope, absolutely not. I wouldn't use your circuit for a charger of such
    nature.. I was only trying to be nice to the originator asking for a
    sensible circuit that would fit properly and safely, for their needs.

    I think you flatter yourself a little too much, you really should
    think of others and instead of passing on what you would like to ignore.

    We have charging stations at work and none and I mean none of the
    chargers are allowed to exceed 10% of the battery voltage, regardless of
    condition. You on the other hand, would think it's ok to boil the
    battery off, even after its has reached the peak voltage.

    Personally, I don't care what you do with your own cells, you can do
    what ever and take a chance of generating undesirable effects if you
    wish. It's your choice, but to give others advise with out taking that
    into consideration, thinking that maybe they don't care any more than
    you do is pure foolishness.

    BTW, that circuit you posted can be modified very simply to add
    limiting voltage function, but since you're so self centered I'll allow
    you the honor or making a mess out of it.

    Jamie
     
  15. Jamie

    Jamie Guest

    You failed ! Grossly,... And don't drag Jim in on your failures, he's
    getting old and can't help what he does..

    Jamie
     
  16. Jamie

    Jamie Guest

    I never asked for your story nore do I care to hear it.

    As for me being a registered radio operator, I have no idea what that
    has to do with you throwing a tantrum.

    The radio part is just a hobby to take me away from my regular duties.

    I can't help it if you get all teary eyed when some one calls
    you out on the advise you give out.

    You better get used to people pointing out your design failures. It
    happens to the best of them, even though at times don't want to
    fess up to it.


    Jamie
     
  17. Jamie

    Jamie Guest

    Such a miss informed performer, what do you do for encores?

    Jamie
     
  18. Jamie

    Jamie Guest

    Yeah, Maynard has a web sight. If you are a window licking drooler with
    both eyes going in opposite directions, you can get what ever you want,
    sunshine!

    Jamie
     
  19. Jamie

    Jamie Guest

    It's sad to see what age can do to some. Mental degeneration must
    be common among the elderly.

    Jamie
     
  20. Jamie

    Jamie Guest

    I think I hear your mother calling you.

    Jamie
     
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