Simple Charge indicator???

Discussion in 'The Projects Forum' started by latrevino, Jun 30, 2013.

  1. latrevino

    Thread Starter New Member

    Jun 30, 2013
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    0
    I'm trying to make a simple charge indicator using a transitor on a 12v project that will turn on a led or flash a led once it gets to 10.5-10.8 volts!!
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,995
    745
    use an op amp as a comparitor.

    opamp
     
    Last edited: Jul 1, 2013
  3. latrevino

    Thread Starter New Member

    Jun 30, 2013
    2
    0
    Would like to make blink at the given voltage drop? Would you have a schematic of a built circuit for a 12+ volt system that will indicate at 10.5-10.7 volts to blink led.??
     
  4. wayneh

    Expert

    Sep 9, 2010
    12,128
    3,049
    You need a 555 timer IC circuit to build yourself an LED flasher. Just look for it on this site, authored by Bill Marsden. Lots of options.

    As noted, you can then use a comparator to turn the flashing circuit on when the system voltage sags. You need a voltage reference to "calibrate" the comparator. I would use resistor voltage dividers to divide down the system voltage, to compare to your reference. For instance if you use a 5V zener diode as your reference voltage, you will divide your system voltage by ~2 to tell when the divided voltage falls below the reference. With a variable resistor as your divider, you'll be able to dial in whatever setpoint you want.
     
  5. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,995
    745
    Flasher circuit

    Simply make the comparator circuit , set the preset VR2 to make the op amp go high(pin 6) at 10.8v, and then connect it to the flasher circuit on pin4 of the timer ic, this will make the flasher work at the set voltage, use a 6v1 zener for the reference.
     
    Last edited: Jul 1, 2013
  6. BillB3857

    Senior Member

    Feb 28, 2009
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