Hi

I am trying to build a voltage comparator which should drive the green led ON only when voltage lies between 12 to 9 v and should drive the red led ON when the voltage falls below 9v.

For this I tried with LM 393 as well as lm 339 but couldn't get htrough with it.
My Findings:

1. With LM 393((pin8)Vcc:5v,(pin4)Vdd:0v,non inverting(pin3),inverting(pin2))

I have used 2 different presets for the 2 i/p terminals to vary the voltage.

Whatever be the situation,ie
a)-i/p>+i/p or
b)+i/p>-i/p

o/p always remains high.

I have tried many other configurations as well.

Gone through many sites and with different circuits but can not find that small bit where i am going wrong .

Your support would be highly appreciated .

Thanks in Advance

Tarun

 

Look here: http://www.free-circuit.com/12v-battery-voltage-monitor-circuit-with-lm339-comparator/

If your battery is lead-acid, look here: http://forum.allaboutcircuits.com/showpost.php?p=262143&postcount=38