Simple LED Voltmeter Circuit

This circuit is like a tiny battery level indicator, but with fancy lights.

Instead of a boring bar on your phone, it uses a series of LEDs light emitting diodes to show you how much juice is left in your battery.

Each LED lights up at a certain voltage level so the more LEDs that are glowing, the fuller the battery.

This circuit also uses special diodes zener diodes and resistors to make sure the LEDs get the right amount of electricity to shine bright.

So, with a little glance you can always know how much power your battery has left.

Circuit Working:

Parts List:

This is a basic LED voltmeter designed to monitor the charge level of lead acid or tubular batteries.

It uses four LED indicators to show the batteries terminal voltage.

Lead acid batteries typically have a nominal terminal voltage of 13.8V while tubular batteries have 14.8V when fully charged.

The LED voltmeter employs four zener diodes to illuminate the LEDs at the exact breakdown voltage of the Zener diodes.

Generally, the zener diode needs to exceed its specified value by 1.6V to reach the breakdown threshold.

When the battery holds 13.6V or more, all the zener diodes break down and all the LEDs light up.

When the battery discharges below 10.6V all the LEDs remain off.

Thus, depending on the batteries terminal voltage the LEDs light up or turn off one by one.

Formula:

The above circuit diagram displays the battery voltage using an array of resistors and LEDs.

When the voltage across the resistors reaches their forward voltage, the LEDs turn on.

The resistors split the electricity from the battery.

The voltage across each resistor may be determined using the following formula:

V = I * R

here,

• V is the resistors voltage across it.
• I represents the current passing via the resistor.
• R is the resistors resistance.

The amount of current passing through the resistors and the LEDs is the same.

This results from the series connection of the resistors and LEDs.

When an LED conducts current, the voltage drop across it is known as the forward voltage of the LED.

A red LEDs forward voltage is normally about 1.8V.

You may use the following calculation to get the voltage between each LED:

V = Vf + Vr

here,

• V is the LEDs voltage across it.
• Vf is the LEDs forward voltage.
• Vr is voltage drop across the resistor in series with the LED .

The noise in the battery voltage is removed by the capacitor C1.

The intended filtering properties can be taken into consideration while selecting the capacitors value.

How to Build:

To build a Simple LED Voltmeter Circuit follow the below mentioned steps:

• Connect the positive terminal of the battery to one end of the resistor.
• Connect the other end of the resistor to the anode longer lead of the first LED.
• Connect the cathode shorter lead of the first LED to the anode of the first zener diode.
• Connect the cathode of the first zener diode to the anode of the second zener diode.
• Repeat this process for the remaining LEDs and zener diodes connecting them in series.
• Connect the cathode of the last zener diode to the negative terminal of the battery.

Note:

• Make sure to test the circuit with a power source before connecting it to your battery.
• Adjust the resistor values if necessary to ensure that the LEDs light up at the desired voltage levels.

Conclusion:

A LED voltmeter circuit is a cost effective and basic way to monitor the voltage level of a power source.

By using LEDs and zener diode as indicators, these circuits provide a visual display of the voltage, making them useful in various applications where voltage monitoring is necessary.

Whether in automotive systems, battery chargers or other devices LED voltmeter circuits offer a simple and efficient solution for voltage level indication.

References:

Digital Voltmeter – TriColor LED Output

Voltmeter