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How to Use pc817 optotransistor: Examples, Pinouts, and Specs

Image of pc817 optotransistor
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Introduction

The PC817 is a widely used optocoupler or optoisolator that consists of an infrared emitting diode (IRED) and a phototransistor. This electronic component is designed to transfer electrical signals through light waves, providing an optical isolation between its input and output. The PC817 is commonly used in applications requiring high-voltage insulation, signal isolation, and noise reduction, such as microcontroller interfacing, DC-DC converters, and signal transmission between different voltage circuits without direct electrical connection.

Explore Projects Built with pc817 optotransistor

Use Cirkit Designer to design, explore, and prototype these projects online. Some projects support real-time simulation. Click "Open Project" to start designing instantly!
ESP8266 NodeMCU Controlled Relay with AC Bulb and Opto-isolated Input
Image of IoT LOAD CONTROL: A project utilizing pc817 optotransistor in a practical application
This circuit uses an ESP8266 NodeMCU to control a relay via a PC817 optocoupler and BC547 transistor, allowing for the switching of an AC-powered bulb. The circuit includes a protective diode for the relay, an LED indicator, and employs resistors for current limiting and signal interfacing.
Cirkit Designer LogoOpen Project in Cirkit Designer
LDR-Controlled LED Dimmer with LM358 Op-Amp and NPN Transistor
Image of Light-Sensor-Based-Switch: A project utilizing pc817 optotransistor in a practical application
This circuit is a light-sensitive LED controller. It uses a photocell to detect ambient light levels and an LM358 Op-Amp to compare the light level against a set threshold, adjustable via a potentiometer. When the light level is below the threshold, the Op-Amp activates an NPN transistor to power an LED.
Cirkit Designer LogoOpen Project in Cirkit Designer
LM324-Based Analog Light Sensor with LED Indicators
Image of 2: A project utilizing pc817 optotransistor in a practical application
This circuit is designed to detect varying light levels using phototransistors and process these signals with LM324 operational amplifiers. The output of the amplifiers may be used to activate LEDs, indicating the presence or absence of light. Trimmer potentiometers allow for adjustment of the detection thresholds, and resistors are used for current limiting and biasing.
Cirkit Designer LogoOpen Project in Cirkit Designer
Wi-Fi Controlled Octocoupler Circuit with Wemos D1 Mini
Image of Opto: A project utilizing pc817 optotransistor in a practical application
This circuit uses a Wemos D1 Mini microcontroller to control an optocoupler, which in turn interfaces with an external system. The microcontroller drives the optocoupler through a 220-ohm resistor, allowing for electrical isolation between the microcontroller and the external connections.
Cirkit Designer LogoOpen Project in Cirkit Designer

Explore Projects Built with pc817 optotransistor

Use Cirkit Designer to design, explore, and prototype these projects online. Some projects support real-time simulation. Click "Open Project" to start designing instantly!
Image of IoT LOAD CONTROL: A project utilizing pc817 optotransistor in a practical application
ESP8266 NodeMCU Controlled Relay with AC Bulb and Opto-isolated Input
This circuit uses an ESP8266 NodeMCU to control a relay via a PC817 optocoupler and BC547 transistor, allowing for the switching of an AC-powered bulb. The circuit includes a protective diode for the relay, an LED indicator, and employs resistors for current limiting and signal interfacing.
Cirkit Designer LogoOpen Project in Cirkit Designer
Image of Light-Sensor-Based-Switch: A project utilizing pc817 optotransistor in a practical application
LDR-Controlled LED Dimmer with LM358 Op-Amp and NPN Transistor
This circuit is a light-sensitive LED controller. It uses a photocell to detect ambient light levels and an LM358 Op-Amp to compare the light level against a set threshold, adjustable via a potentiometer. When the light level is below the threshold, the Op-Amp activates an NPN transistor to power an LED.
Cirkit Designer LogoOpen Project in Cirkit Designer
Image of 2: A project utilizing pc817 optotransistor in a practical application
LM324-Based Analog Light Sensor with LED Indicators
This circuit is designed to detect varying light levels using phototransistors and process these signals with LM324 operational amplifiers. The output of the amplifiers may be used to activate LEDs, indicating the presence or absence of light. Trimmer potentiometers allow for adjustment of the detection thresholds, and resistors are used for current limiting and biasing.
Cirkit Designer LogoOpen Project in Cirkit Designer
Image of Opto: A project utilizing pc817 optotransistor in a practical application
Wi-Fi Controlled Octocoupler Circuit with Wemos D1 Mini
This circuit uses a Wemos D1 Mini microcontroller to control an optocoupler, which in turn interfaces with an external system. The microcontroller drives the optocoupler through a 220-ohm resistor, allowing for electrical isolation between the microcontroller and the external connections.
Cirkit Designer LogoOpen Project in Cirkit Designer

Technical Specifications

Key Technical Details

  • Forward Current (IF): 50mA (max)
  • Reverse Voltage (VR): 6V (max)
  • Collector-Emitter Voltage (VCEO): 35V (max)
  • Emitter-Collector Voltage (VECO): 6V (max)
  • Collector Current (IC): 50mA (max)
  • Isolation Voltage (Viso): 5000Vrms (min)
  • Current Transfer Ratio (CTR): 50% to 600% at IF=5mA, VCE=5V
  • Response Time (tr): 18µs (typ), 100µs (max)
  • Operating Temperature: -30°C to +100°C

Pin Configuration and Descriptions

Pin Number Name Description
1 Anode (A) Anode of the infrared emitting diode
2 Cathode (K) Cathode of the infrared emitting diode
3 Collector (C) Collector of the phototransistor
4 Emitter (E) Emitter of the phototransistor

Usage Instructions

How to Use the PC817 in a Circuit

  1. Connecting the Input Side (LED):

    • Connect the anode to the positive side of the input signal.
    • Connect the cathode to the negative side of the input signal through a current-limiting resistor.
  2. Connecting the Output Side (Phototransistor):

    • Connect the collector to the positive side of the output circuit.
    • Connect the emitter to the negative side of the output circuit.
  3. Current Limiting Resistor Calculation:

    • Calculate the current-limiting resistor for the LED side using Ohm's law: R = (Vin - Vf) / If, where Vin is the input voltage, Vf is the forward voltage of the LED (typically 1.2V), and If is the desired forward current (typically 10-20mA).

Important Considerations and Best Practices

  • Ensure that the input and output circuits are properly isolated to prevent electrical noise and high-voltage transients from affecting the low-voltage side.
  • Do not exceed the maximum ratings of the device to avoid damage.
  • Use a pull-up resistor on the collector of the phototransistor for proper operation.
  • Consider the current transfer ratio (CTR) when designing your circuit to ensure adequate signal transfer.

Troubleshooting and FAQs

Common Issues

  • No Signal Transfer: Check if the input LED is properly forward-biased and the current-limiting resistor is correctly calculated.
  • Weak Output Signal: Ensure that the CTR is within the required range for your application and that the phototransistor is not saturated.
  • Device Damage: Verify that the device is not exposed to voltages or currents beyond its maximum ratings.

Solutions and Tips

  • If the LED does not light up, check the input connections and the current-limiting resistor.
  • For a weak output signal, adjust the value of the pull-up resistor or check the input current to the LED.
  • Use a multimeter to check the continuity of the PC817 pins to ensure the device is not damaged.

FAQs

Q: Can the PC817 be used to isolate high-voltage circuits? A: Yes, the PC817 provides electrical isolation up to 5000Vrms, making it suitable for high-voltage applications.

Q: What is the purpose of the current-limiting resistor on the input side? A: The current-limiting resistor protects the LED from excessive current, which could lead to damage or reduced lifespan.

Q: How do I choose the pull-up resistor value for the phototransistor? A: The pull-up resistor value depends on the voltage level of the output circuit and the desired collector current. It can be calculated using Ohm's law, considering the CTR and the collector-emitter voltage.

Example Code for Arduino UNO

// Example code for interfacing PC817 with Arduino UNO

const int inputPin = 2; // Input pin connected to the phototransistor
const int ledPin = 13;  // Onboard LED pin for output indication

void setup() {
  pinMode(inputPin, INPUT); // Set the phototransistor pin as input
  pinMode(ledPin, OUTPUT);  // Set the LED pin as output
}

void loop() {
  int sensorValue = digitalRead(inputPin); // Read the value from the optotransistor
  if (sensorValue == HIGH) {
    digitalWrite(ledPin, HIGH); // Turn on the LED if the sensor is triggered
  } else {
    digitalWrite(ledPin, LOW);  // Turn off the LED otherwise
  }
}

Remember to include a current-limiting resistor for the LED side of the PC817 when connecting it to the Arduino. The example assumes that the PC817 output is connected to pin 2 and that the onboard LED is used as an output indicator. Adjust the pin numbers as necessary for your specific circuit design.