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Battery Level Indicator

Carlos Nunes

Nov 13, 2017
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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
 

kellys_eye

Jun 25, 2010
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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?
 

Alec_t

Jul 7, 2015
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Also, what type of battery? Depending on the chemistry, the voltage may or may not be a good indicator of the state of charge.
 

Carlos Nunes

Nov 13, 2017
11
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Nov 13, 2017
Messages
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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?
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
 

Harald Kapp

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Nov 17, 2011
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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.
 

kellys_eye

Jun 25, 2010
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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
 

dorke

Jun 20, 2015
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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
 

WHONOES

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