the PC817 Phototransistor Optocoupler is an essential component for protecting sensitive control circuitry from high-voltage spikes and electrical noise. At Electrapac, we recommend this 4-pin IC for any project where an Arduino, ESP32, or PIC microcontroller needs to switch a load that operates on a different power supply.

Product Overview

The PC817 consists of an Infrared Emitting Diode (IRED) optically coupled to a Phototransistor. It provides complete electrical isolation between the input and output sides. Because there is no physical wire connection between the two sides—only a beam of light—voltage surges on the output side cannot travel back to destroy your expensive microcontroller.

Key Features for Electrapac Customers

• Total Galvanic Isolation: With a 5000V isolation rating, it acts as an "electrical firewall," keeping your logic circuits safe from motor noise and AC power surges.

• Signal Level Shifting: Easily bridge the gap between a 3.3V logic signal and a 12V or 24V industrial control system.

• Compact DIP-4 Design: Occupies very little space on a PCB or breadboard, making it more efficient than using bulky mechanical relays for low-current switching.

• Noise Suppression: Effectively filters out electromagnetic interference (EMI) that can cause "false triggers" in digital inputs.

• Versatile Switching: Can be used to drive transistors, MOSFETs, or small relays available at www.electrapac.com.

Standard Wiring Logic

To use the PC817 correctly in your Electrapac builds, follow this 4-pin configuration:

1. Anode (Pin 1): Connect to your Microcontroller output pin through a current-limiting resistor (typically 220Ω to 470Ω)

2. Cathode (Pin 2): Connect to the Microcontroller Ground.

3. Emitter (Pin 3): Connect to the Ground of the external/high-voltage load.

4. Collector (Pin 4): Connect to the positive side of the high-voltage load or a pull-up 

   Primary Applications

   • Microcontroller I/O Protection: Shielding Raspberry Pi or Arduino pins from inductive kickback.

   • Switch Mode Power Supplies (SMPS): Providing feedback from the output side to the controller while maintaining safety isolation.

   • Industrial PLC Interfacing: Converting 24V factory signals into 5V logic for data logging.

   • Ground Loop Elimination: Solving "hum" or data corruption issues in long-distance communication lines.

   • Relay Driving: Acting as the "pre-stage" to trigger high-power relays safely.

   Why Shop at Electrapac?

   We source the PC817 with high Current Transfer Ratio (CTR) consistency to ensure your logic transitions are sharp and reliable. At www.electrapac.com, we provide the safety components that ensure your innovations don't just work—they last.