In many industrial and DIY applications, isolating control circuits from high-power or noisy electrical environments is crucial for safety, performance, and reliability. One of the most common ways to achieve this isolation is by using optocouplers. Optocouplers (or optoisolators) are electronic components that use light to transmit signals between two isolated circuits, providing electrical isolation while maintaining high-speed data transmission.
In this DIY electronics project, we will build a temperature monitoring system using the PS11036 optocoupler. The PS11036 is a high-performance optocoupler specifically designed for isolating and protecting sensitive low-voltage circuits from high-voltage components. It is ideal for applications where isolation is critical, such as in temperature sensing and monitoring systems, particularly those involving microcontrollers, sensors, and high-voltage machinery.
This project will involve using the PS11036 in conjunction with a NTC thermistor (temperature sensor) to monitor temperature readings, which will then be transmitted via optocoupler to a microcontroller for processing and display.
Project Overview
The temperature monitoring system we’ll design is aimed at industrial or home automation applications, where high voltage might be present, and it’s crucial to isolate sensitive circuits for safety and functionality. In this system:
A NTC thermistor will sense the ambient temperature.
The temperature data will be passed through an analog-to-digital converter (ADC) within a microcontroller.
The PS11036 optocoupler will isolate the analog circuit from the microcontroller, providing protection against voltage spikes or electrical noise.
The microcontroller will process the temperature data and display the readings on an LCD screen.
The project will demonstrate how the PS11036 can be used to isolate different parts of a circuit while maintaining efficient data transmission.
Components Required
● PS11036 Optocoupler (Phototransistor output)
● NTC thermistor (temperature sensor)
● Microcontroller (e.g., ATmega328P or ESP32)
● 10kΩ resistor (for the thermistor divider network)
● LCD Display (16x2 or similar)
● Breadboard and jumper wires
● Power supply (5V regulated)
● Resistor (for the optocoupler LED input)
● Transistor (optional, for driving high-current loads)
● Pull-up resistors (for optocoupler output)
● Capacitors (optional, for noise reduction)
● Arduino IDE (for programming, if using an Arduino-compatible microcontroller)
The Role of the PS11036 Optocoupler
The PS11036 is a phototransistor optocoupler with a high-current transfer ratio, meaning it can efficiently transmit electrical signals with great isolation between the input and output sides. The optocoupler is particularly useful in noisy environments where electrical isolation is required, such as with the thermistor sensor, which may be subject to noise or voltage spikes. The optocoupler will ensure that the sensitive microcontroller circuit remains protected from such interference while still receiving the correct signals for processing.
In our system, the PS11036 will isolate the analog output from the thermistor sensor from the digital side of the circuit, where the microcontroller resides. The optocoupler will convert the analog voltage signal from the thermistor into a digital signal, which can then be processed by the microcontroller.
Step 1: Preparing the Thermistor Circuit
The first step in building the temperature monitoring system is setting up the temperature sensing circuit. NTC thermistors change resistance with temperature, making them ideal for temperature sensing. The most common way to use an NTC thermistor is in a voltage divider configuration, where the thermistor's resistance changes as the temperature varies.
In this case, we will set up a simple voltage divider with a 10kΩ resistor and the thermistor. Here's how the circuit will work:
● The thermistor will be placed in series with the 10kΩ resistor.
● One end of the series pair will be connected to the 5V supply.
● The other end will be connected to the analog input pin of the microcontroller.
● The midpoint between the thermistor and the resistor will provide a voltage that changes depending on the resistance of the thermistor, which in turn changes with the ambient temperature.
The voltage at the midpoint will vary based on the temperature, and the microcontroller will use this voltage to determine the temperature of the environment.
Step 2: Integrating the PS11036 Optocoupler
Once the thermistor circuit is complete, it’s time to integrate the PS11036 optocoupler. The PS11036 will act as an isolator, protecting the microcontroller and the sensitive analog side of the circuit.
● Input Side (LED side of the PS11036): We connect the LED side of the PS11036 to the voltage divider’s output (the thermistor’s voltage). The LED side of the optocoupler requires a current-limiting resistor to protect it from excessive current. A typical value for this resistor might be 330Ω.
● The LED side of the optocoupler will receive the varying voltage signal generated by the thermistor. As the voltage varies, the optocoupler’s LED will turn on and off, generating light that is transmitted to the phototransistor side.
● Output Side (Phototransistor side of the PS11036): The phototransistor side of the optocoupler will output a signal to the microcontroller. We connect the collector of the phototransistor to the microcontroller’s input pin (e.g., PORTD). A pull-up resistor will be placed between the phototransistor’s collector and the supply voltage to ensure that the output is stable when the phototransistor is not conducting.
As the LED side of the optocoupler fluctuates with the thermistor’s voltage, the phototransistor will switch accordingly, creating a digital signal that the microcontroller can process.
Step 3: Interfacing with the Microcontroller
Now, we need to interface the optocoupler output with the microcontroller. The PS11036 optocoupler is capable of transmitting a digital signal, which the microcontroller can read using a simple digital input pin.
● Digital Input Pin: The output of the optocoupler is connected to a digital input pin on the microcontroller. Depending on the voltage from the thermistor, the optocoupler will either pass a high or low signal, which will correspond to the varying temperature data.
● Pull-up Resistor: A pull-up resistor is added to the output of the optocoupler to ensure that the signal is stable when the optocoupler is not active.
At this point, the microcontroller is ready to receive data from the temperature sensor circuit via the optocoupler. The signal received will be processed as a digital value that corresponds to the analog voltage from the thermistor, and the microcontroller can then convert this value into a readable temperature.
Step 4: Displaying the Temperature
To visualize the temperature, we will use an LCD display. The microcontroller will convert the digital signal from the optocoupler into a temperature value using a simple algorithm or lookup table (since the thermistor’s resistance vs. temperature relationship is known). This temperature value will then be displayed on the LCD.
● LCD Display: The microcontroller communicates with the LCD to display the temperature reading. A 16x2 character LCD can be used to show the temperature in Celsius or Fahrenheit, depending on your preference.
● Processing the Signal: The microcontroller will process the digital data from the optocoupler, apply any necessary scaling, and display the corresponding temperature on the LCD.
Step 5: Testing and Calibration
After the system is assembled, it’s time to test the temperature monitoring system. Use a known temperature source, such as a room thermometer, to verify that the system is correctly reading temperatures and displaying them on the LCD. If necessary, calibrate the system by adjusting the thermistor’s resistance readings to match the known temperature.
Conclusion
The PS11036 optocoupler is a powerful and versatile component for electrical isolation, and in this DIY project, it served as the bridge between a temperature-sensing circuit and the microcontroller, protecting the microcontroller from any electrical noise or high-voltage spikes while still transmitting accurate temperature data.
By isolating the analog side (the thermistor sensor circuit) from the digital side (the microcontroller), we created a safe, reliable temperature monitoring system that can be used in environments where electrical isolation is critical. Whether for home automation or industrial applications, this project demonstrates how the PS11036 optocoupler can be used in real-world scenarios to enhance the robustness and safety of your electronic systems.