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low voltage indicator

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hemnath

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I have used LTV3401 as a comparator for low battery indication. Current - Quiescent (Max) is 950nA. But costs 2USD

Is it possible to use the transistors for the low battery indication. But the circuit should consume very low current. COST EFFECTIVE

Input voltage: 9V (Battery 6F22)

Output will be fed to the microcontroller input pin to detect the voltage as 0 or 1. So that I can able to display the LOW BAT on the display.
 

You can use simple zener diode compactor or transistor compactor for low voltage battery indicators
V Indicator .png
 

Below is the LTspice simulation of a circuit that should work for you.
It uses a TLV431 low-power programmable reference (about U$0.60) as a comparator with a built in 1.25V reference voltage.
The output goes high when the Ref voltage drops below 1.25V.
The U2 pot is shown adjusted to give an output high when the 9V battery drops below 6V.

Capture.PNG
 

the circuit should consume very low current
Click to expand...
How is microcontroller supplied? Has it switched power supply or operated in sleep mode most of the time?

My standard solution is measuring battery voltage with voltage divider and µC ADC. A transistor switch is isolating the voltage divider in idle state.
 

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