# How to Make a Car Battery Voltage Monitor Circuit

This easy 4 LED car voltmeter is made to enable us to observe the voltage level of the battery of our car at any moment, always.
To obtain the above function it has got to be positioned somewhere in the dash of the car to ensure that the group of 4 LEDs continue to be protruded, each with a label indicating the battery voltage having at that instant.
The circuit is meant for performing the following:
– 1st LED lights with 11V battery
– 1st and 2nd LEDs light with battery 12V
– 1st, 2nd and 3rd LEDs light with battery 13V
– 1st, 2nd, 3rd and 4th (all) LEDs light with battery 14V
Operational aspect of the Car Battery Voltmeter/Monitor Circuit.
When the battery voltage falls to 11 or 12 volts, it might require charging. If its around 13 volts it is in appropriate situation. At 14 volts it is completely charged. The colors of the LEDs show these position.
The main elements of the circuit are simply a couple of functional amplifiers utilized as comparators.
The inverting inputs associated with these functional are set at fixed reference voltages: 5.1, 4.8, 4.4, 4.1 utilizing zener diode D1 and resistor network: R1, R2, R3 and VR potentiometer.
The VR potentiometer is employed to create minor adjustments to the above referenced voltages, which may differs simply because the resistors are not precise values.
The battery voltage is brought to non-inverting inputs of the opamps by means of the presented voltage divider networks created by R4 and R6 terminals.
Based on the battery voltage, the voltage at the non-inverting terminal will be different and will put a high voltage level at the output of the comparator, signaling the related LED for the needed indications.

Car Battery Voltage Monitor Circuit making use of LEDs and IC LM324
Parts list for the circuit
– IC1: LM324 integrated (quad opamps in a single integrated) Circuit
– D1: 3.3V zener diode, 1/4 watt
– D2 = D3 = D4 = D5: Diodes LED (2 red, 1 yellow or amber, 1 green)
– R1 = 1K
– R2…..R6: all 1K preset
+12V: is the car battery whose voltage is usually to be felt