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Battery & Power Supply Detection

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contagiouseddie

contagiouseddie

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I need to know how to detect whether the power supply is coming from an external source or from the battery. I'm using a 3.3 V LDO regulator from Micrel and the output is in series with a diode. The battery is parallel with that diode and also comes with a diode. I attached the circuit here. Can I take the output of the regulator to know the power source as indicated by the red dotted line in the circuit. The MCU is taking power from the VCC point.

Thank you very much.
 

I can't see any reason why not ..
Just make sure that the voltage is within MCU's input range and if it is to high use a simple voltge divider ..

Regards,
IanP
 
Hi, No problem. Better put a resistor in series with you I/O line !!.

If you MCU is running and I/O line is low its battery time !! otherwise Mains time :).

Paul.
 
I have got the ideal ! you should comparator voltage of two source, if battery greater, Vcc = battery and against.
Good luck for U !
 
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