3V Battery Indicator Circuit?

  • #1
Hi,

I'm not sure if this is the right place to post this, but here goes.

I'm trying to build a battery indicator circuit for 2 AA batteries (3V). So far what I've read online is that I'd need to use a Zener diode to get a fixed voltage drop, then connect it to a transistor, like the diagram here:
http://www.4qdtec.com/batty.html" [Broken]

Only problem is, the smallest Zener diode is 2.4V, so the difference between the base and the emitter would be very small - 0.6 V - even when the battery is fully charged.

Will this work?
 
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Answers and Replies

  • #2
Drakkith
Staff Emeritus
Science Advisor
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If you don't get help here, try the Electrical Engineering forum. They should be able to help you there.
 
  • #3
46
0
Are you looking at this schematic?

blow.gif


Typical diodes have a 0.6-0.7 V drop when forward biased, so you could use a few of those in series.
 
  • #4
Yup I'm looking at that schematic, which is for a 6V battery.

Thanks Sciurus, I didn't think of that even though I have a few diodes lying around. So I guess instead of a Zener diode in reverse bias, I could just use (say 3) normal diodes in forward bias to get a 2.1V voltage drop, so the voltage difference between the base and the emitter is around 0.9 V when the battery is fully charged, and decreases as the battery is drained?
 

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