Car LED Voltmeter Circuit using IC LM324

A Car LED Voltmeter Circuit is a really useful tool that helps keep track of the voltage levels in a cars battery.

It makes sure that these levels stay safe and work properly.

This circuit uses LEDs to show different voltage levels making it easy to understand the batteries condition at a glance.

The main part of this circuit is the LM324 operational amplifier which acts like a voltage checker and is important for measuring the voltage.

A voltmeter is a device that measures the voltage difference between two points in a circuit.

It can be either analog or digital depending on how it shows the readings.

In this circuit the voltmeter is cleverly made using LEDs and the LM324 operational amplifier which, provides a simple way to see the batteries voltage levels.

This design makes it easier to monitor the battery by lighting up different LEDs for specific voltage levels helping you quickly check how healthy the car battery is.

Circuit Working:

Parts List:

In this article the circuit gets its power straight from the car battery.

It works by comparing the batteries voltage to certain set voltage levels.

The main part of this circuit is the IC LM324 which has four operational amplifiers that act as comparators.

To set the reference voltage a 5.6V Zener diode is used along with a resistor divider.

There is also a preset VR1 that allows for fine tuning of the reference voltage.

The resistors labeled R2 to R5 help create different voltage levels for comparison.

To show the battery voltage status there are LED1 to LED4.

Each LED is connected through a 1k resistor which are from R7 to R10.

The job of each comparator is to check the battery voltage against a specific level, which controls whether the corresponding LED lights up.

If the battery voltage goes above a certain point the related LED turns on to show that status.

If the voltage drops below that point the LED goes off giving a clear visual signal about whether the battery voltage is at 14V, 13V, 12V or 11V.

It is important to note that if the voltmeter shows a voltage of 12 volts or more from the car battery, that is a good sign meaning the battery is in decent shape.

But if the voltage drops below 12 volts down to 11.6 volts, it means the battery is starting to lose charge.

If the voltage keeps going down there are two main possibilities: either the battery is failing or it might have low water levels.

Formulas with Calculations:

The below mentioned are the formulas with calculations for Car LED Voltmeter Circuit using IC LM324

The Voltage Divider Formula:

A resistor divider network helps set the reference voltage for each comparator.

The formula used is:

Vref​ = Vz​ × Rx​​ / Rtotal​

where,

• Vz​ is the Zener diode voltage of 5.6V

Comparator Operation:

Each LM324 op-amp compares the battery voltage with its respective reference voltage:

If Vbattery>Vref the comparator output is HIGH than the LED turns ON

If Vbattery​<Vref​ the comparator output is LOW than the LED remains OFF.

LED Current Calculation:

The LED series resistor is calculated using ohms law:

R = V − Vf / I

where,

• V is the output voltage of the comparator
• Vf is the forward voltage of the LED around 2V
• I is the desired current around 10mA.

How to Build:

To build a Car LED Voltmeter Circuit using IC LM324 following steps are needed to be followed:

• Gather all the components as mentioned in the above circuit diagram
• Connect pin 1 of IC1 LM324 to one end of resistor R7 and other end of R7 to anode of LED1 and cathode of LED1 GND.
• Connect resistor R2 one end from positive supply and other end to pin 2 of IC1 LM324.
• Connect resistor R1 one end to positive supply and other end to pin 3 of IC1.
• Connect resistor R3 between pin 2 and pin 6 of IC1.
• Connect pin 3, pin 5, pin 10 and pin 12 of IC1 to Non-Inverting Input
• Connect resistor R4 between pin 6 and pin 9 of IC1.
• Connect resistor R5 between pin 9 and pin 13 of IC1.
• Connect a VR1 preset center leg to pin 13 of IC1 and second leg to GND.
• Connect resistor R6 from pin 12 of IC1 and GND.
• Connect resistor R7, R8, R9 and R10 and LED1(14V), LED2 (13V) , LED3(12V) and LED4(11V) from pin 1, pin 7, pin 8 and pin 14 of IC1 and GND.
• Connect a cathode of D1 diode from pin 2 of IC1 and anode of D1 to GND.
• Connect pin 4 of IC1 to positive terminal of car battery
• Connect pin 11 of IC1 to negative terminal of the car battery

Conclusion:

This Car LED Voltmeter Circuit using IC LM324, which uses LED lights is a simple and efficient tool for checking your car batteries voltage.

It features the LM324 quad op-amp as a comparator which keeps the circuit affordable and simple to assemble.

The LED lights display various voltage levels allowing users to easily see the batteries condition and take the right steps to keep it running well.

References:

Arduino LED Voltage Meter