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Using LM3914 To Masure 3VDC - 4.2vDC [HELP]

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penguino

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Hello, So I have built a minty boost portable iPod charger that runs off of a 3.7VDC LiPo battery, this part works beautifully. I also need to have a battery indicator on this project. I am going to use a 10 segment LED graph to show the output from a LM3914. Anyway I need to know what resistor values I need to use to make this work on that voltage scale. Also, I am not too sure on the voltage I need to run the LM3914. Could I just use voltage off the battery to go to the V+ on the chip, and the signal on the chip? Any other thoughts, useful tips or ideas would also be greatly appreciated.
Thanks in advance.
 
Open blogs in this site and search for "LM3914".

You'll find a file named DualLM3914a.exe (published by ericgibbs) which you might use to calculate any values to be displayed by 10 LEDs.

Here are the values I found for the first until the 10th LED to illuminate from 3.7 to 4.2V input voltage (VIN, pin5):

RLO (pin4) (VEXTLO)=3.64V, RHI (pin6) (VEXTHI)=4.20V, R1 (pin7 to pin8)=3.9KΩ, REFADJ 9.35KΩ (trimpot).

Supply voltage used is 5V. (might be any other, since the LM3914 won't care unless max supply voltage is exceeded.)

Verify the values and build your circuit accordingly.


Boncuk
 
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