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9V Low Battery Indicator Circuit

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9V Low Battery Indicator Circuit

Hi,

I just had a question about how I could use a 12V instead of 9V.

Also, what are the values that I should change to let the green LED on from 11.5V and above and the red LED on below 11.5V?

I think it's the resistor values in front of the base but not sure about the calculations.

 

Thanks,

Connor
asked May 5 by yunw00naver-com (120 points)

1 Answer

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Here is an old circuit I found on line.  Replace the 741 with a low current Op-amp.  Use a LED in place of the zener then you can operate it on a few uA,  Change the pot to about 500K  and add a 1.5 Meg resistor in series.  Most LEDs have a sharper knee then a Zener especially at low currents.  You can then add a resistor to to the output to two LEDs connecting one to + and the Other to -.  At the transition point expect them both to be on varying in brightness as the threshold is crossed. This is a starting point I did not do any of the calculations for you.

 

Image result for high low circuit

answered Sep 27 by gilshultzhome-com (17,730 points)

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