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Battery Level Indicator

Discussion in 'Power Electronics' started by Carlos Nunes, Nov 13, 2017.

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  1. Carlos Nunes

    Carlos Nunes

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    0
    Nov 13, 2017
    Hi
    Can you please help me with the following:
    I am on an electronic cource and have a project. I would like to get a circuit for a Battery Level Indicator and those I get have the LM3914 IC but I need one circuit without IC, only LED's.
    Thank you vey much
    Best regards
     
  2. kellys_eye

    kellys_eye

    4,275
    1,146
    Jun 25, 2010
    Define 'battery level indicator'..... do you want to know it's level 'intimately' or just when it's falling below acceptable limits?

    There are methods that offer bar displays (LM3914) for a graduated indication - go/no-go LED displays with Red, Yellow and Green indications (often used in automotive battery indicators) or simple 'LED comes on if the voltage falls below 'x' volts' circuits.

    The LM3914 version can be done using op-amps, transistors or the dedicated device itself. The other versions can all be achieved using discrete parts only.

    So.... what type of indication do you require?
     
  3. Alec_t

    Alec_t

    2,927
    797
    Jul 7, 2015
    Also, what type of battery? Depending on the chemistry, the voltage may or may not be a good indicator of the state of charge.
     
    kellys_eye likes this.
  4. Carlos Nunes

    Carlos Nunes

    11
    0
    Nov 13, 2017
    Hi
    Thank you so much for your reply.
    Yes, I've seen that most of the circuits on all sites I've checked are using th LM3914 but I want to do it without that. Maybe using OPAmps.
    It's to do as the LM3914 does.
    Regards
     
  5. Carlos Nunes

    Carlos Nunes

    11
    0
    Nov 13, 2017
    Hi Alec
    Can be a car battery.
    Regards
     
  6. Harald Kapp

    Harald Kapp Moderator Moderator

    11,008
    2,506
    Nov 17, 2011
    The block diagram of the LM3914 in the datasheet page 8 shows how the chip is constructed. You can build this exact structure from comparators or opamps and resistors.
     
    Carlos Nunes likes this.
  7. Carlos Nunes

    Carlos Nunes

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    0
    Nov 13, 2017
    Thank you very much Harald Kapp
     
  8. kellys_eye

    kellys_eye

    4,275
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    Jun 25, 2010
    You can wire an op-amp as a comparator, set the detection level to whatever you wish and have the output transition when the measured voltage falls below the set voltage.

    You can an wire op-amp as 'window comparator' that has three states of output - too high, too low or 'just right'.

    Google image search for a battery meter schematic and there are a gazillion results such as this:

    meter.png
     
  9. dorke

    dorke

    2,342
    665
    Jun 20, 2015
    Here is another simple way to do it( i think you can't beat that simplicity).:cool:

    Using only a Zener diode as a comparator.Like the 1N47xx series
    It isn't very accurate , but should be good enough.
    If more accuracy is needed/wanted ,you can use the TL431 instead of the zener.

    calculate the resistors...and choose the LEDs colors. untitled.JPG
     
    Harald Kapp likes this.
  10. WHONOES

    WHONOES

    1,099
    309
    May 20, 2017
    If all you want to do is see your battery voltage, use a small analogue panel meter. Simple and cheap.
     
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