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Battery Indicator

Since I didn't get any replies to my "Voltage Cut off circuit" post, here is plan B. How about a circuit with 3 to 5 small LEDs of various colors that would each come on at a different voltage. That wouldn't be too hard to make would it? I would have some kind of momentary button to activate it so it didn't run the battery down all the time.

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Chris W
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Chris W
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You can use a LM339 comparator and some resistors and zener diode to indicate 5 voltage ranges. Here's an example for a 12 volt lead acid battery.

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-Bill

Reply to
Bill Bowden 

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Geez, don\'t be so impatient.

I was working on a circuit for you that would draw less than 1mA
using a latching relay and a couple of comparators, but if it\'s a
real rush job I\'m afraid I\'ll have to quit since the pay\'s a little
low for that.

Matter of fact, forget it. 

Maybe you can get someone else to help you out, I\'m no longer
interested.
Reply to
John Fields

Hi Chris, Putting couple of LEDs to indicate the battery level is not a good idea since those LEDs will drain the batteries even faster than the device it self. Look at this link.

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it has a good circuit.

Pubudu.

Reply to
pubuducg

Sorry John I didn't mean to be impatient, normally responses come pretty quick in this group, I only posted this second message because after thinking about the problem more, it seemed like a lot easier solution and I was seriously wondering if my previous request was even practical. Sounds like you had a solution though.

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Chris W
KE5GIX

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Reply to
Chris W

Yeah that one's fairly easy depending on how complex and/or precise you want to get.

google for "bar graph" schematic for a few ideas.

Bye. Jasen

Reply to
jasen

I found a circuit using an LM3914. On page 11 of this PDF file...

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it gives a good example of the kind of thing I am trying to do. However the battery being tested will also be the power source for the whole circuit. I states that V+ (pin 3) needs to be at least 1.5V higher than the Sig (pin 5). I guess the way to do that would be to put a resistor between pin 5 and the battery. I'm not sure how to calculate what size resistor I need there. Also I'm not sure what other resisters need to be changed to, so my range can be 11 to 13.5V instead of the 4.46 to

5.54 that circuit is set up for. 
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Chris W
KE5GIX

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Reply to
Chris W

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