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 Simple LED 12 Volt Lead Acid Battery Meter
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kcarring
Moderator


Canada
1057 Posts

Posted - April 12 2012 :  00:23:09  Show Profile Send kcarring a Private Message  Reply with Quote
In the circuit below, a quad voltage comparator (LM339) is used as a simple bar graph meter to indicate the charge condition of a 12 volt, lead acid battery. A 5 volt reference voltage is connected to each of the (+) inputs of the four comparators and the (-) inputs are connected to successive points along a voltage divider. The LEDs will illuminate when the voltage at the negative (-) input exceeds the reference voltage. Calibration can be done by adjusting the 2K potentiometer so that all four LEDs illuminate when the battery voltage is 12.7 volts, indicating full charge with no load on the battery. At 11.7 volts, the LEDs should be off indicating a dead battery. Each LED represents an approximate 25% change in charge condition or 300 millivolts, so that 3 LEDs indicate 75%, 2 LEDs indicate 50%, etc.



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AaronOran
New Member



1 Posts

Posted - May 04 2012 :  05:13:22  Show Profile Send AaronOran a Private Message  Reply with Quote
Does anybody manufacture a LED light

Edited by - AaronOran on May 04 2012 05:19:54
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49er
Administrator



USA
4442 Posts

Posted - May 04 2012 :  09:46:18  Show Profile Send 49er a Private Message  Reply with Quote
Hi Aaron

Yes you can find a led light just about every where

Doug
The sky is not the limit...There are footprints on the MOON.
Your only as DUMB as where your standing.
No matter where you go there you are.
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shakamuni01
Average Member



USA
213 Posts

Posted - May 04 2012 :  19:49:43  Show Profile Send shakamuni01 a Private Message  Reply with Quote
thanks Kcarring. This looks like a good first project working with an IC which I have only done in my head.
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shakamuni01
Average Member



USA
213 Posts

Posted - May 04 2012 :  19:50:50  Show Profile Send shakamuni01 a Private Message  Reply with Quote
maybe I can hook it up to a servo via my arduino as an automatic switch/regulator
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shakamuni01
Average Member



USA
213 Posts

Posted - May 04 2012 :  19:54:56  Show Profile Send shakamuni01 a Private Message  Reply with Quote
Couple questions actually-

the 2k resistor is a variable one that is supposed to be adjusted for acuracy?
where it says 5.1 - is that a diode?- seems to have a squigley line
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kcarring
Moderator



Canada
1057 Posts

Posted - May 04 2012 :  22:50:23  Show Profile Send kcarring a Private Message  Reply with Quote
Shaka,

That is a zener diode :) 5.1 volts

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You wouldn't laugh at my igloo if you knew how cold my beer is!
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