Voltmeter circuit using LED
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
- 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.
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