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does any body know how to make a led battery tester?

does any body know how to make a led battery tester for a 9v battery that has 3/4 leds.

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I'd look into the LM3914 bargraph LED driver. This chip is used to create a bar graph voltmeter display. The datasheet for the part will have all the details on how to scale the input voltage to the range you want. It is normally used for 10 LED bar graph displays, but there is no reason you couldn't use it with only 4 LEDs, as long as the voltage range it scaled so that the 4 LEDs represent voltages in a range of , say, 7 volts to 10 volts. The datasheet has several sample circuits if I recall, and there are lots of circuits based on the LM3914 on the web, etc.

Then it is just a matter of connecting a reasonable load across the 9V battery under test. Use a resistor value that will draw a current comparable to a "typical" device that uses a 9V battery. About 10mA current at 9V would probably be a good guess, but I don't know the most suitble load current off hand.

The tester will measure the voltage of the battery under load.
techxpert (author) 5 years ago
thanks i found a 0-5v schematic to
can you put add the link you found for the schematic that shows the 0-5v lm3914 display? i would like to view it.
thanks!
techxpert (author)  metal_head_mike5 years ago
http://www.futurlec.com/Linear/LM3914N.shtml

the first picture on the pdf