2B-Volt Meter Made of LEDs




This project indicates the voltage condition of a 12V lead acid car battery.  The charging position of battery is also indicated by this.  The glow of LEDs tells us the position of battery.  There are 10 numbers of LEDs used in this project.  The charging condition of battery is known by reading the voltage written near glowing LED.  This project is very simple and made very easily.

Technical Description & Working System


This project has been developed and tested OK in our TV Engineering Technical LAB.  The components and PCB used in our books are available for sale.  You can receive the project through post giving your order giving project code no.  The information about project code is given in the beginning and last pages in the books.  You can give your order through telephone.


IC LM3914 is used in this project.  It is also used in the audio level indicator circuit.  Here it is used in DOT MODE.  The LED connected at pin no. 1 IC shows the 10.5V [Lower Voltage Limit].  This is adjusted with the help of preset VR1.  The LED connected with pin no. 10 shows the 15V [Higher Voltage Limit].  This is adjusted by preset VR2 [4.7KE].  To indicate the voltage of battery in the circuit 10 LEDs are used.  LEDs no. 1,2 & 3 are of red colour which indicate the low voltage.  The LEDs number 4, 5, 6, 7 & 8 are of green colour,  which indicates the normal voltage of battery.  The LEDs number 9 & 10 should be used of high bright red colour.  Which will indicate the overcharging position of the car  battery.


After assembling this circuit on PCB provide a regulated variable supply and digital multimeter.  Connect the circuit with supply and adjust for 10.5V.  Set the preset VR2 [4.7KE] so that LED 1 glows on this voltage.  After this 15V supply is given and preset VR1 [4.7KE] is adjusted so that LED number 10 glows.  After this voltage is increased from 10.5V to 15V in steps of 0.5V.  The connected LED should glow and be OFF after the change of 0.5V supply.  Thus this project is ready to indicate voltage variation for your car battery.


Precaution While Assembling the Project


  1. Use IC base for fixing the IC on PCB. 2. Take care that while soldering there should be no short on PCB. 3. First of all, check all the components so that they are according to the circuit and OK. 4. While soldering LEDs take care of its cathode and anode leads. 5. Always use good quality presets.