Introduction
For electronics enthusiasts and hobbyists, working with sensitive circuits often requires isolation between different parts of a system. Isolation helps prevent damage from voltage spikes, ground loops, and interference from noisy signals. One useful tool for achieving this isolation is an isolation amplifier. In this project, we will design a voltage monitoring system that uses the ISO103B isolated amplifier to monitor voltage levels from a high-voltage circuit while keeping the low-voltage control circuit safe.
The ISO103B is a precision, galvanically isolated amplifier, which makes it perfect for this project. It isolates the measurement circuit from the system under test, ensuring safety while also providing accurate feedback. Our project will use this component to monitor the voltage from a high-voltage circuit, providing a safe and accurate way to read these voltages without risking damage to the low-voltage electronics.
This project is ideal for users who want to build a practical and safety-conscious system for voltage monitoring, especially for high-voltage systems like industrial equipment, power supplies, or even renewable energy systems like solar panels.
Materials Required
To build this voltage monitoring system, you will need the following components:
● ISO103B Isolated Amplifier (x1)
● Resistors:
— 10kΩ (x2)
— 100kΩ (x2)
— 1kΩ (x1)
— 470Ω (x1)
● Capacitors:
— 100nF (x2)
— 1µF (x1)
— 10µF (x1)
● Voltage Reference IC: LM4040 (x1)
● Diodes:
— 1N4148 (x2)
● Op-Amp: TLV2372 (x1)
● Voltage Source: 12V DC (Power supply)
● Microcontroller: Arduino or any other microcontroller for display and control (optional)
● LCD Display: 16x2 LCD or a similar display to show voltage readings
● PCB or Breadboard for the circuit assembly
● High-voltage circuit (to test and monitor, such as a power supply or battery bank)
These components are easily accessible from electronics suppliers, and many of them are commonly used in a variety of other electronics projects.
Project Overview
The goal of this project is to build a system that reads the voltage from a high-voltage source and displays it on an LCD or sends it to a microcontroller for further processing. The ISO103B will be used to isolate the measurement circuit from the high-voltage system, ensuring safety while still allowing for precise voltage measurements. The isolated output from the ISO103B will then be fed to an op-amp to amplify the signal, and the resulting voltage will be processed by the microcontroller or displayed directly on an LCD.
Step 1: Understanding the ISO103B
Before beginning the build, it’s important to understand how the ISO103B operates. The ISO103B is an isolation amplifier with a single-ended input and a differential output, meaning it can read the voltage difference between two points while ensuring that no direct electrical connection exists between the two circuits.
The key features of the ISO103B are:
● Galvanic isolation: It electrically separates the low-voltage and high-voltage sides of the circuit, ensuring there is no direct connection.
● High precision: It provides accurate voltage readings, making it suitable for monitoring tasks.
● Single-ended input: You can input a single reference voltage and monitor the voltage differential.
In this project, the ISO103B will be connected to a voltage divider to step down the high voltage to a manageable level, and the output will be routed through an op-amp for further processing.
Step 2: Preparing the Power Supply and Voltage Divider
Start by preparing the 12V DC power supply, which will power the low-voltage side of the system. The high-voltage system under test could be a source such as a battery bank or power supply with a voltage in the range of 100V-300V.
The first step in interfacing the high-voltage source with the ISO103B is to use a voltage divider. The voltage divider will scale down the high voltage into a range suitable for the ISO103B’s input. Since the ISO103B operates on a differential signal, the voltage divider will reduce the input voltage to match the input range of the ISO103B, which typically operates with an input voltage of around 0-5V.
Using resistors, we create a voltage divider that takes the high input voltage and reduces it to a fraction that the ISO103B can handle. This voltage is then fed to the amplifier, which will convert it into a signal that is isolated and ready for further processing.
Step 3: Setting Up the ISO103B Isolated Amplifier
Now that the power supply and voltage divider are in place, it’s time to set up the ISO103B itself. The ISO103B has a single-ended input that connects to the voltage divider circuit and a differential output that can be used for further processing.
● Input connections: Connect the output of the voltage divider to the input of the ISO103B. The input should be connected between the reference ground (GND) and the high-voltage point you wish to monitor.
● Power supply: The ISO103B requires a single power supply, which in this case will be provided by the 12V DC source. Connect the positive terminal of the power supply to the VCC pin of the ISO103B, and connect the ground to the GND pin.
● Output connections: The output of the ISO103B is differential, meaning it has two output terminals: one for the positive and one for the negative signal. These outputs will be sent to the next stage of the circuit for signal processing.
Step 4: Amplifying the Output Signal
Although the output from the ISO103B is isolated, it may not be at the level required to be read by the microcontroller or displayed on an LCD. To amplify the signal, we will use a TLV2372 operational amplifier.
● Op-Amp Setup: The op-amp will take the differential output from the ISO103B and amplify it so that the microcontroller can read the voltage level. The op-amp will also help filter any noise from the signal and ensure that the output is clean and precise.
● Feedback Resistors: Use appropriate feedback resistors to adjust the gain of the op-amp. The op-amp will boost the signal and output it to the microcontroller or LCD display.
Step 5: Signal Processing with the Microcontroller
The output from the op-amp will be connected to an analog input pin on the microcontroller (such as an Arduino). The microcontroller will read the voltage and either display it on a connected 16x2 LCD display or use it for other purposes, such as logging data or triggering an alert if the voltage exceeds a threshold.
For simple projects, the voltage reading can be directly displayed on an LCD with a basic program, or more advanced systems can store data to be reviewed later.
Step 6: Calibration and Testing
Once the circuit is assembled, you should calibrate it to ensure that the voltage readings are accurate. Begin by testing the system with a known voltage source, such as a calibrated power supply or voltage reference. Compare the readings from the system with the expected values, and make any necessary adjustments.
Calibrating the system involves:
● Ensuring the voltage divider properly scales the input voltage to a safe range.
● Adjusting the gain of the op-amp to ensure the output is within the microcontroller's readable range.
● Fine-tuning the system to ensure accurate voltage monitoring.
Step 7: Final Assembly and Housing
Once the circuit has been tested and calibrated, it is time to package everything into an enclosure. The voltage monitoring system should be housed in a suitable enclosure that protects the components from environmental damage, ensures safety, and prevents accidental contact with high-voltage parts.
Make sure the high-voltage side of the circuit is properly shielded and separated from the low-voltage control side to maintain safety.
Conclusion
Building a voltage monitoring system using the ISO103B isolated amplifier is an excellent way to explore isolation techniques and develop a practical system for safely monitoring high-voltage circuits. By following this project, you not only gain hands-on experience with an isolation amplifier but also learn how to design systems that provide both safety and accuracy.
The key takeaway from this project is the use of galvanic isolation to protect sensitive components while still allowing for accurate voltage monitoring. With the ISO103B and the op-amp stage, you’ve created a circuit that can handle high-voltage inputs, process them safely, and display or use the data in a meaningful way. This project provides a solid foundation for more advanced work in industrial automation, power systems, and high-voltage electronics.