LED flash after 2sec and gets solid when LI battery fully charged

Discussion in 'The Projects Forum' started by Engr1, Mar 10, 2016.

  1. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    Hello;
    Can any body tell is it possible with a opamp to get a LED flash after 2 sec and gets solid when LI ion battery gets fully charged.
    Is their any option to achieve this by sensing battery voltage or current?
    Battery cutoff at 4.1v
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Use an opamp comparator and flasher osc, or use a deadicated chip for the battery.

    Mcp7831
     
    Last edited: Mar 10, 2016
  3. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    If you're thinking of making a lithium end of charge indicator - don't do it!!!

    You need to terminate charging at the specified terminal voltage, over charged lithium cells tend to vent with flaming gas, sometimes the metal cased ones rupture violently.

    The method I've been getting away with is a shunt regulator, but this still requires some monitoring/intervention.

    Someday I must get around to building a topping charge timer.
     
  4. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    I am using a charge controller IC so its not a issue for me to cutoff battery when fully charge only issue is the indication scenario i needed.
     
  5. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,516
    1,246
    Not sure what you mean by "flash after 2 sec", but you probably can do this with a dual comparator like an LM393 (or a newer, ultra-low power part). One comparator acts as a comparator, and the other is configured as an oscillator and LED driver.

    ak
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    Just select a charge control chip that has a full charge indicator pin - I though most of them did.

    If you want the LED to flash until charged then stay on continuously, just use a 2 transistor astable and the full charge signal to make it stay flipped one way.

    E-cigarette charge control chips just disconnect the charge when full, the indicator just senses current draw by the battery.
     
  7. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    I am attaching circuit diagram please refer to it and provide a circuit diagram in here.
     
  8. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,438
    368
    It would have saved a lot of guessing if you'd put that in your first post.

    If you can clarify what "LED flash after 2 sec and gets solid when LI ion battery gets fully charged" means I'm sure a solution is not far away? It appears that it already provides a solid LED indication when the battery is charged.
     
  9. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    I already answered that question - flash the LED with an astable, and use the battery full pin to jam it so the LED stays on.
     
  10. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    Can any body tell where to put full charge signal?
     
  11. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    File is uploaded the question is where to connect the pin7 of charging IC to astable multi vibrator which flashed and gets solid.
     
  12. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Connect the flasher circuit to bat positive and pin 7 for flashing at full charge,

    for flashing during charge connect between pin7 and bat negative.
     
    Last edited: Mar 14, 2016
  13. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    Not required flashing at full only need flashing when battery is under charge.Can both flashing and solid can be achieve with one LED?
     
  14. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,516
    1,246
    What is the IC U1? Manufacturer? Part number?

    ak
     
  15. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Yes, flashing and steady can be achieved with one led, using a 555 timer in astable mode with the led between pins 3,8... and using pin4 as the signal from the lion charger,

    This will give flashing when finished and steady when charging,

    Or just use a flashing led on the lion chip.
     
  16. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    Pin 4 needs resistor divider as well what to do with that?
     
  17. Engr1

    Thread Starter New Member

    Nov 4, 2011
    9
    0
    Attach please find the LED flasher circuit diagram when battery attached to circuit LED flashes but when battery full it goes off how to get it solid ON? any idea.
    Need flash when battery under charge
    Solid when full (how to get this?)
    NO LED indication in presence of battery.
     
Loading...