PC817 Optocoupler — Single-Channel, DIP-4, 5kV Isolation, 50mA Output

PC817 Optocoupler — Single-Channel, DIP-4, 5kV Isolation

The PC817 is a widely-used single-channel phototransistor optocoupler providing 5kV isolation voltage between input and output. An internal LED on the input side drives a phototransistor on the output side — with no electrical connection between them — allowing safe signal transfer between circuits at different voltage levels or ground potentials. Essential for isolating microcontrollers from mains-connected circuits, relay drivers, and industrial control systems.

Key Specifications

Parameter	Value
Channels	1
Isolation Voltage	5kV (AC, 1 minute)
Input LED Forward Voltage	1.2V typical
Input LED Forward Current	50mA max
Output Collector Current	50mA max
Output Collector-Emitter Voltage	35V max
Current Transfer Ratio (CTR)	50–300% @ IF=5mA
Response Time	~4µs
Package	DIP-4 (through-hole)

Why Use an Optocoupler?

• Galvanic isolation — completely separates input and output circuits with no electrical connection
• Protect microcontrollers — isolate Arduino/Raspberry Pi GPIO from high-voltage or noisy circuits
• Ground loop elimination — connect circuits with different ground references safely
• Noise immunity — optical coupling is immune to electromagnetic interference on the signal path

Typical Applications

• Isolating Arduino GPIO from relay driver circuits
• Mains zero-crossing detection with microcontroller isolation
• Industrial PLC input/output signal isolation
• Isolating UART/serial communication between different voltage systems
• Feedback isolation in switching power supplies
• Motor driver enable signal isolation

Basic Wiring (Arduino to Relay)

PC817 Pin	Connection
Pin 1 (Anode)	Arduino GPIO via 330Ω resistor
Pin 2 (Cathode)	Arduino GND
Pin 3 (Emitter)	Output circuit GND
Pin 4 (Collector)	Output circuit load / pull-up

Package Contents

• 1× PC817 Optocoupler (DIP-4)

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