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Daniel.ru92
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« on: October 31, 2012, 08:25:49 AM »

I have new project - I'm building boombox with 12v battery like that:
http://www.zbattery.com/B-B-12V-20Ah-10-hr-rate-Sealed-Lead-Acid-Battery

Now, I want to build electronic circuit that when I'll push a switch, one of three LEDs will turn on:
If the battery is full charged, the green led turn on.
If the battery have anough energy, the yellow led turn on.
If there is low battery, the red led turn on.
If the battery is charging (connected to power supply), all three LEDs will turn on (or another blue led, if it's too hard).

Please help me plan the easiest schema, so I can build it just with buying the right parts, and put it together on electronic board...

Thanks!
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audioguru
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« Reply #1 on: October 31, 2012, 12:22:21 PM »

It is simple to use a quad opamp as 3 or 4 comparators. A stable reference voltage can come from a biased zener diode. The inputs to the opamps come from resistor voltage dividers.
Add some hysteresis to prevent blinking at the threshold voltage.

I recommend a quad opamp instead of an LM339 quad comparator because they can drive the LEDs brightly.

Recently I heard very good sound far way at the park. I went to see and it was a car radio with a 10" subwoofer and two 6.5" 2-way door speakers mounted in a big picnic cooler on wheels. It had a huge car battery in there.
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Daniel.ru92
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« Reply #2 on: October 31, 2012, 01:39:41 PM »

Can you please draw it in schema for me? I don't know to draw it myself...
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