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power LED's

greenwald1818

hi,

     I was wondering, im building a raspberry pi laptop, and I need a way to tell if the battery is low. so, what part would I need to get if I get 2 LED'S, and I want the blue one to be on if the battery is full and the amber one to be on if it gets below 4.5 volts (with a 7.5 volt battery) OR if I have a multi-colored one how would I do it if the same thing applies except with a multi colored one. thx in advanced.

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  • 0 in reply to greenwald1818

    Hi Alex,

     

    I don't know of any links to do exactly what you wish to achieve, but the LM3915 datasheet has a block diagram to give you an idea of how to achieve it with a comparator. You'd still have to design the circuit. Similarly for an ADC method, you could search for potential divider to see how to divide the input voltage to a range suitable for the Arduino ADC (assuming this is what you choose - just a suggestion in case you were already using it as part of your design). Code to read the ADC can be found by searching for 'arduino adc' - it is an AnalogRead function. To make an LED turn on, the DigitalWrite function can be used I believe (I'm not knowledgeable on Arduino, but I know it can be done with it - the arduino.cc website has example code).

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