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wireengineer1-Visitor
1-Visitor
July 30, 2010
Question

12v battery monitor circuit help

  • July 30, 2010
  • 1 reply
  • 3385 views

Hi all!

Looking for a circuit that monitors a 12v battery and indicates visually or audio when the voltage drops below 10v. I have found this circuit....

http://www.discovercircuits.com/DJ-Circuits/9vbatmon1.htm

but i am unsure on how to change the input voltage to 12v and the cut off voltage to 10v.

Thanks in advance!

1 reply

I
IRstuff1-Visitor
1-Visitor
July 30, 2010

OK, you need to do more work on your end. The LTC1440 http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1154,C1002,C1463,P1172 is rated only for a max supply of 11 V. So, you need to find something similiar that operates to around 15V for some operating margin, or configure something that will either drop the voltage to the chip, or generate a lower voltage supply.

The LTC comes with its own threshold reference, nominally 1.182 V. Hence, the resistor divider is scaled to produce a input of 1.46, and the circuit will trip if the voltage drops below 7.29 V. Since you want it to trip at 10V, you need a resistor divider that gives you 1.182V/10V = 0.1182 divider ratio.

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