Battery level detector

Discussion in 'General Electronics Chat' started by freezerburn73, Apr 21, 2009.

  1. freezerburn73

    Thread Starter New Member

    Apr 21, 2009
    1
    0
    Could anyone help me out with a circuit to turn on an LED when the battery drops below voltage threshold? I am using this on a rc helicopter. Trying to prevent crashes.
    thanks,
     
  2. suntop

    New Member

    Feb 9, 2008
    4
    0
    use only high value R (a few resistors) and LEDs in series-parralal branch If you need Discrete levels of voltages, No IC required
     
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    2,574
    230
    Interesting! I'm not visualizing it. Do you have a schematic?

    Ken
     
  4. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    Sounds like an interesting project. It must provide your crash indicator without significantly reducing your fly time.

    You can use a low power comparator. Feed your divided down battery voltage into one terminal (+) and a reference voltage, from a zener diode or actual reference, into the other (-). Comparators like the National LMV7291 draw pretty small currents. I am not sure about which reference voltage you should use.

    You will need to add some hysteresis to the comparator for stability purposes unless you don't mind the LED blinking a little while the voltages are getting close. This might actually help with power consumption.
     
  5. tkng211

    Well-Known Member

    Jan 4, 2008
    65
    2
    You can use the 3 terminal voltage reference IC TL431 (in TO 92 package) circuit. Please refer to the following link: http://homepages.paradise.net.nz/bhabbott/lvw.html
    If you can't find the IC from the electronic parts store nearby your place, get it from some on line shop such as www.epartgrocer.com.
    I think the circuit can meet your requirement. Have fun!
     
  6. StayatHomeElectronics

    Well-Known Member

    Sep 25, 2008
    864
    40
    That is certainly a much better solution than the one I proposed. Thanks.
     
  7. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The LM10 is low current, 8 pins and has an adjustable voltage reference (200mV and up) and an opamp that can be used as a comparator.
     
  8. Stevezachtech

    New Member

    Apr 21, 2009
    4
    0
    You could also look for an electronic junk shops and get cheaper electronic parts. Good luck in turning on your LED when the battery drops below voltage..
     
  9. sakbal

    New Member

    Jun 23, 2007
    3
    0
    Here is a little Low battery circuit that has served me well over the years.

    Use R1 to set the trip Voltage. At that voltage the Led should just come on.

    The circuit is currently configured for a 6 volt battery. Change the zener as required.
     
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