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LED Voltage Indicator: 4 DIY Projects You Can Create

LED Voltage indicator

Source: Wikimedia Commons

An LED voltage indicator is an essential tool you should consider if you plan to build measuring equipment with accurate results.

However, creating a DIY LED voltage indicator or implementing it in your existing project could be a bit tricky.

That’s why we created this article specifically for you.

Here, we’ll be defining the LED voltage level indicator circuit and showing a ton of non-hazardous voltage projects you can build with the device.

So, if you’re ready, let’s get started.

What Is an LED Voltage Indicator?

Digital Voltage Indicator

Digital Voltage Indicator

Source: Wikimedia Commons

In straightforward terms, an LED voltage indicator is used to monitor both direct and alternating voltage levels—using LED lights. Hence, they are perfect for measuring the current threshold voltage of an electronic device. You can also use the indicator to monitor the constant current level of the mains or batteries.

Also, you can change the voltage value of a  scalable LED level voltage indicator to a consequent measuring quantity. 

In some cases, you’ll find an LED level voltage temp indicator measuring temperature and current—asides from measuring AC and DC voltages. So, the LED display shows the voltage values and presence of voltages. Moreover, you can use it for various electronic appliances.

4 DIY LED Voltage Indicator Projects

Here, we will be looking at four LED voltage indicator projects you can do at home.

1. Simple Voltage Level Indicator Using Zener Diode

Voltage indicator using Zener Diode

Voltage indicator using Zener Diode

Source: Youtube (Creative Commons)

This section will show you how to build a voltage level indicator with a Zener diode.

So, a Zener diode breaks down when your electronic device reaches a specific voltage level. And it conducts current when a reverse bias occurs in a circuit. Hence, the Zener diode’s breakdown voltage is responsible for the current that performs across the course.

Required Components

  • LED
  • 220Ω resistor
  • 1N4733 5.1V Zener Diode


1. First off, you connect the Zener diode to a power source—in a reverse bias mode. Afterward, install the 220Ω resistor to the circuit. By doing this, you’ll be limiting current to the LED. Also, the power source will be supplying voltage to the board.

2. Next, you can create alterations to your circuit by interchanging different diodes to get various voltage thresholds.

3. Then, you can solder your setup on a circuit board, protect it with cardboard or paper tape, and reduce the LED lights.

4. Lastly, mark the various voltage levels on the indicator—by using a marker on the paper tape or cardboard.

2. Easy On-Off Indicator With Two LEDs

Easy On-Off Voltage Indicator 

Easy On-Off Voltage Indicator 

Source: Research Gate

The “on-off” battery indicator is a pretty easy LED circuit project for beginners.

Required Components

  • LEDs (2)
  • 1000uF capacitor
  • SPDT Switch (On & Off switches)
  • 9 Volts Battery


1. First, connect the on and off switches to the 9 volts battery.

2. Next, join the two LEDs together with the resistor and capacitor connected at the right and left sides, respectively. Then, click the “ON” switch, and the current immediately enters the circuit. By doing this, LED2 turns off, and LED1 briefly comes on and off. If you click the “OFF” switch, LED1 goes off, and LED2 briefly comes on and off.

When you switch on the indicator, current flows via the resistor into LED 1. Then, the indicator Light briefly comes on and off while the capacitor starts charging. When the capacitor becomes fully charged, LED1 switches off. So, nothing happens to LED1  because of the reverse-biased voltage.

3. Battery Auto Cut Off/Level Indicator for 12 Volts Battery

Battery Auto Cut-Off Indicator

Battery Auto Cut-Off Indicator

Source: Research Gate

Here, we’re going to show you how to create a battery capacity level indicator—with the aid of LM3914 IC. We’ll also show you how to add an essential feature to your current battery charger. And how to cut off charging voltage when your battery charge is complete.

Required Components

  • Voltage regulator LM3914 (U1)
Voltage regulator LM3914 (U1)
  • LED lights (10)
LED lights (10)
  • Resistors (5)
Resistors (5)
  • Capacitors (2)
Capacitors (2)
  • 12CDC Relay (J1)
  • Voltmeter (P1)
  • 1N4001 Diode (D1, D2)
1N4001 Diode (D1, D2)
  • Input (CN1)
  • Charger (CN2)


1. Create a Schematic design. The main idea is to create a battery level indicator design before combining the components.

2. Design your PCB. After creating your schematic design, the next is to make your PCB design. You can also choose to buy your PCB from a reputable PCB manufacturer

3. Gather all the components and required tools together. So, it would help if you had a soldering wire, pliers, soldering wire, and a multimeter in your arcade of tools—asides from the components.

3. Assembly all your components on the PCB—by soldering them to the board. While soldering, ensure you install the LM3914 IC with the correct notching direction. Hence, it’s ideal to use a handy IC holder that you can easily replace—if it gets damaged.

4. Finalize Your Project. After assembling, the next thing to do is connect the 12v battery to the circuit. Then, calibrate the device based on the lower and upper voltage battery limits. And you can achieve this by making use of the two variable resistors. After linking the load to the battery, check its charge level and disconnect the pack if your battery charge is complete.

Also, you can choose to connect a relay to the battery charger. That way, if the battery gets to maximum charge, the supply shuts down. So, it’s an excellent charge control feature you can add to this project.

4. How to Create LED AC Voltage Indicator Circuit

LED AC mains voltage indicator

LED AC mains voltage indicator

Source: Research Gate ℅ Joni Welman Simatupang

This section will discuss how to produce an LED AC voltage indicator circuit. You can use this LED AC voltage indicator circuit to showcase the voltage level of 120V or 220V mains home AC input.

Required Components

  • Transformer (O – 6 Volts/ 500ma)
  • Capacitor (1000uf/25v)
  • 1n4007 Diode (D1)
  • Red Diffused LED (5) (5mm)
  • Resistors (10) (1 K ¼ Watt, CFR)
  • Transistors (5) (Bc547)
  • Preset (5) (47k Linear)
  • 6” X 2” General Purpose Board
  • Zener Diode (5) (3 Volts / 400mw)


1. Follow the circuit diagram above and arrange all the required components in an organized manner.

2. Next, join the transformer to the AC mains with your soldering iron. Then, combine the transformer’s secondary output to the circuit’s negative point.

3. Afterward, assemble the alligator wire/clip and solder the end of the wire to 1n4007 Diode.

4. The next thing is to join the alligator clip to the transformer’s 3 Volt output. Then, tweak the P1 until the LED1 starts glowing.

5. Join the clip to the transformer’s 12, 9, 7,5, and 6 volts. Then, tweak the remaining P5, P4, P3, and P2 for the suitable LEDs to flash at various voltages.

6. Last but not least, insert the 6-volt transformer into the PCB. Afterward, switch the power on, and the three LEDs will glow.

The Bottom Line

No doubt, with the information gotten here about an LED voltage indicator, you can build your DIY project. In short, you can choose to do any of the four projects. But, if you’re a beginner or newbie engineer, we advise you to start with the Easy On-off Battery Indicator Using Two LEDs.

Finally, before kicking off with your project, ensure you get the high-quality components—especially the PCB and LEDs. At OurPCB, we produce sturdy and reliable PCBs and LEDs you can use for your LED voltage indicator project.

So, feel free to reach us today with your needs, and we’ll get back to you swiftly.

Hommer Zhao
Hi, I am Hommer, the founder of WellPCB. So far, we have more than 4,000 customers worldwide. If you have any questions, you can feel free to contact me. I really appreciate any help you can provide.