Build a 0–99 0V & 0–99 9A | Digital Panel Meter Using IC 7107 | No Programming Required | JLCPCB

In this project, I will show you how to build a compact and accurate digital voltage and current meter using the IC 7107. The meter can measure voltages from 0 to 99.0 volts and currents from 0 to 99.9 amps, displaying the results on bright 0.56-inch seven-segment LED displays. The PCB for the project was ordered from JLCPCB.

Unlike many modern designs that rely on microcontrollers, this project does not require any programming. All measurement and display functions are handled by dedicated hardware, making the circuit simple, reliable, and easy to build.

The meter features a push-button-controlled flip-flop circuit that allows switching between voltage and current measurement modes. Two indicator LEDs show the active measurement mode.

This project is ideal for bench power supplies, battery chargers, laboratory equipment, and many other electronics applications.

Features

1. Measures 0 to 99.0 volts
2. Measures 0 to 99.9 amps
3. Based on the IC 7107
4. Bright 0.56-inch LED display
5. Push-button mode selection
6. Voltage and current mode indicators
7. No programming required
8. Compact PCB design
9. Built from commonly available components

1. IC 7107
2. 0.56-inch common-anode seven-segment displays
3. Resistors
4. Capacitors
5. Diodes
6. Trimmer potentiometers
7. Push button
8. LEDs
9. PCB
10. ±5 volt power supply
11. 0.1 ohm current shunt resistor
12. Soldering tools

The PCB for the project was ordered from JLCPCB.

After uploading the Gerber files, the boards arrived within about one week. The PCB quality is excellent, with clean silkscreen printing, accurate drilling, and a professional solder mask finish. The board layout makes assembly straightforward and helps ensure reliable operation.

Start by assembling the flip-flop section of the circuit.

This section is responsible for switching between voltage and current measurement modes using a push button.

Two LEDs are used as mode indicators. When the push button is pressed, the LEDs should alternate, confirming that the flip-flop circuit is working correctly.

Next, install all remaining components including resistors, capacitors, diodes, sockets, and connectors.

For the best measurement accuracy, use precision components whenever possible and verify component values before soldering.

Careful assembly will help ensure stable and accurate operation.

The displays used in this project are 0.56-inch common-anode seven-segment LED displays.

Be sure to use the correct display type, as common-cathode displays will not work correctly with the IC 7107.

The IC used is the 7107. Different manufacturers may use slightly different part numbers, but as long as the device contains the number "7107," it should be compatible with this design.

The circuit requires a dual power supply.

Connect:

1. Positive 5 volt
2. Ground
3. Negative 5 volt

The center point serves as the circuit ground reference.

Before testing, perform the initial calibration.

Measure the voltage between pin 36 of the IC and ground.

Adjust the calibration trimmer until the measured voltage reaches exactly 1 volt.

This step establishes the correct reference voltage for accurate measurements.

Connect the voltage and current sensing inputs according to the schematic.

For testing purposes, I used a 0.1 ohm, 5 watt resistor as the current shunt.

The voltage drop across this resistor is used by the circuit to calculate the current flowing through the load.

After powering the circuit, verify that the voltage and current readings respond correctly and that the mode selection button operates as expected.

To verify accuracy, I compared the meter readings with two high-precision digital multimeters.

One meter monitored the voltage while the other measured the current.

As the voltage was gradually increased, the readings from the IC 7107 meter closely matched those of the reference instruments. The measurement error was very small, demonstrating excellent accuracy and stability.

Conclusion

The IC 7107 is a powerful and versatile display driver that can be used in many measurement applications beyond simple voltage and current meters.

This project demonstrates how a highly accurate digital panel meter can be built using only commonly available components and without any programming.

The combination of simplicity, low cost, and reliable performance makes this design an excellent addition to any electronics workshop.

Thank you for reading, and I hope you enjoy building this project. Happy making!