Voltmeter circuit using LED

admin February 22, 2011 16 Comments

Car Battery Voltmeter Circuit


This is a very useful circuit which when installed on your car gives the voltage of you car battery in a LED dot display form.The circuit is based on four comparators made of quad op amp LM324.The inverting inputs of IC are kept at at reference voltages 5.6V,5.2V,4.8V,4.4V respectively at pins 2,6,9,13 by resistors ,R3,R4,R5,R6.The battery voltage is directly fed to the pin inverting input through the voltage divider arrangement using R1 and R7.When there is variation in the input supply the out put of each op amp goes high accordingly as they are wired as voltage comparators.The corresponding LED glows.

Voltmeter Circuit Diagram and Parts List

Voltmeter Circuit Diagram

Voltmeter Schematic


  • IC LM 324 consists of4 op amps in one package , so power supply is common and is shown once (pin 4 and 11).
  • To setup , connect  the circuit to battery  ,adjust R6 so that required voltages are available at the inverting pins( refer description to get the required voltages).
  • Fix the LED’s on the dash board and mark the voltages near to it as shown in circuit diagram.The gadget is now ready.

Our website has more related circuits that you may like to read, Take a look:

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  • lrfc
    May 15, 2015

    i have made this circuit and it works but all 4 leds light at a time please can any one tell me what should be the status of leds on varying voltage .i have used simple 9v battery for it..

  • March 30, 2015

    Thanks! is a very easy circuit usint also one IC.

  • Matthew
    August 15, 2012

    For your Car Battery Voltmeter Circuit, would you be able to tell me what resistor values I would need to monitor a 6 V supply? I am looking to build a circuit to visually indicate whether a device is receiving 5.7V-6.3V (Indicating all is well), 3V-5.69V(Might be a short) or Below 3V(basically dead).
    Thanks In advance,
    Matt Bragg

  • Destate9
    May 20, 2012

    First of all, it seems unnecessary to use two pins of the pot (R6). Second of all, I understand this circuit must work for you, however, why did you choose for the LEDs to be powered with the unregulated voltage of your car battery when it can sweep from 11-14 volts? Also, R8-R11 are pretty large for your typical LED resistor. Your probably getting 9-12 mA per LED when they can take up to 20 mA

  • anıl
    May 13, 2011

    selamın aleyküm

  • Conrad
    March 1, 2010

    Super good!

  • […] that V_i=i/N * V_ref for equal resistors. I am currently looking into that, and the diagram here: here. I need the voltages to be 12.6 12.5 12.4 12.24 12.12 12.00 11.9 11.8 volts, so there is a slight […]

  • Munawar
    January 15, 2010

    I am very found to take intrest in Electronic. if you have funny circets then tell me. send me its Digrams
    on my email Adress: computerlinksjhang@yahoo.com .

  • jinesh
    January 13, 2010

    excellent circuit,i am serching for this circuit for a long time..thanks

  • prasanna
    December 29, 2009

    circuit was quite interesting……..

  • Romeo
    November 19, 2009

    How would you change this circuit for voltages less than 4? I teach grade 9 students and a project is a wind turbine. This would be great for them to see some yellow, red and green LEDs

  • August 18, 2009

    tkanks good circuit which i was looking since long.pl keep sending such good circuits for my wv 1958 model .

  • August 18, 2009

    Что-то я почти ничего не понял..

    • admin
      August 18, 2009

      какая часть вам наклоняю понимаю.
      пожалуйста, сообщите мне.
      Я помогу тебе

  • fethi
    June 27, 2009

    salut j ai réalise montage car batterie voltmètre
    les quatre led allumé sur une tension 10 v

  • todd
    December 17, 2008

    I need to build a stop watch display on a lcd or 7 seg to add to my efx-tex prop-xs micro controller!!!this looks like this mite be what I need!!! Can you tell me how to build this!!!

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