PC817 IC Optocoupler Pinout, Circuit, Datasheet, and Uses

An optocoupler, also known as an optoisolator, photo-coupler, or optical isolator, is a semiconductor device facilitating the transmission of electrical signals between two isolated circuits through light. This device comprises two main parts: an LED and a photosensitive component. Various optoisolator ICs are accessible, such as PC817 IC, MOC3021 IC, MOC363 IC, MCT2E IC, and PC817 optocoupler. 

This article delves into the ultimate PC817 IC pinout, circuit, specifications, working, uses, equivalents and datasheet guide. Everything you need to know about the PC817 optocoupler. If you are an electronics enthusiast or a professional engaged in motherboard maintenance, the information provided here will provide practical insights to identify this specific chip.

What is PC817 IC Optocoupler?

The PC817 integrated circuit functions as an optocoupler, incorporating both a phototransistor and an infrared diode that is optically linked. This optical coupling enables the transmission of electrical signals between the input and output sides without needing a physical connection. While it is possible to design the infrared circuit manually, the PC817 optocoupler offers a fully pre-engineered solution with a compact built-in IC circuit.

In various circuits, filters play a crucial role in eliminating noise. When a circuit comprising resistors and capacitors is employed, it effectively removes noise from the incoming signal. However, the choice of resistor and capacitor values often depends on the characteristics of the incoming signal.

This circuit is particularly suitable when the incoming signal carries data, especially when signal transmission between different circuit elements is necessary despite noise. In such cases, a combination of infrared transmission (IR Tx) and reception (Rx) becomes essential.

Within the PC817 optocoupler circuit, the infrared component receives a noisy signal from one part and optically transmits it to another using the infrared signal. This ensures that the circuit operates according to its design. The PC817 IC comprises an LED and a phototransistor, which are optically interconnected. Signal transmission occurs optically between the input and output sides without any physical connection.

It can be directly connected to a microcontroller or any low-voltage DC device. The input voltages from either side of this IC produce a similar effect, merely transmitting the signal to the receiver. Subsequently, the receiver generates a logic signal as an output. The compact size and efficient operation make this IC versatile and applicable in various scenarios.

PC817 Pinout

The illustration depicts the pin diagram, elucidating the role of each pin. Within the PC817 pinout diagram, pin1 and pin2 are components of the input facet, while pin3 to pin4 serve as output interfaces.

Pin Configuration

The pin configuration of the PC817 Optocoupler is delineated as follows. The IC comprises 4 pins, with 2 dedicated to input and 2 to output. The functions of each pin are elaborated upon below.

Pin Name	Pin No.	Description
INPUT
ANODE	PIN 1	Pin 1 is an anode pin of IR input within the Optocoupler. It will give the logical input signal to the internal IR.
CATHODE	PIN 2	Pin 2 is the cathode pin of the IR within the optocoupler. It will give the IR to make the common ground with the circuit and Power supply.
OUTPUT
COLLECTOR	PIN 3	Pin 3 is an output pin of the internal IR receiver of the optocoupler. It will give the logical output by receiving the IR signal.
EMITTER	PIN 4	Pin 4 is a ground pin for IR receiver. It will be used to make the common ground with Power supply and the circuit.

Features & Specifications

Specifications

The PC817 Optocoupler's specifications encompass the following details:

• Forward Voltage of Input Diode: 1.25V

• Maximum Current Ratio at Collector Terminal: 50mA

• Maximum Collector-Emitter Voltage: 80V (max)

• Maximum Voltage Ratio at Collector & Emitter Terminals: 80V

• Maximum Collector Current: 50mA

• Rise Time: 18us

• Fall Time: 18us

• Cut-off Frequency: 80 kHz

• Maximum Operating Temperature Range: -30 to 100 degrees

• Power Dissipation: 200mW

• Internal Resistance: 100 ohms

• Internal Storage Temperature Range: -55 to 125 degrees

• Optocoupler's Temperature Range during Soldering: 260 degrees

• It is crucial to note that exceeding the specified temperature during soldering can damage the IC.

Features

The features of the PC817 IC Optocoupler encompass the following:

• This integrated circuit comprises four pins and is available in two packages: SMT and DIP.

• Internal protection for both input and output from electrical isolation is incorporated, safeguarding up to 5KV.

• When employed with an additional resistor, this IC enables high-voltage devices with lower-voltage counterparts to operate.

• It is versatile in functioning with various device types, including internal interfaces such as Microcontrollers, TTL devices, and high DC voltage, facilitated by internal resistors.

• The PC817 Optocoupler features built-in protection against reverse current, ensuring defense against infrared interference due to unidirectional current flow.

Note: Comprehensive technical details can be available in the PC817 datasheet provided at the end of this page.

How does PC817 IC Work?

The operation of the PC817 is straightforward, yet its utilization with diverse devices involves specific considerations. The input optocoupler necessitates a current-limiting resistor while linking the logic output pin to the power pin, which is essential at the output. Upon generating the IR signal, a transition in the logic state occurs from 1 to 0, prompted by the alteration in current flow.

Circuit Diagram

Presented below is the circuit design.

Though inherently simple, the circuit incorporates resistance to safeguard the input against high voltages. The optocoupler is a compact infrared receiver and sender circuit. However, opting for external construction using separate IR sender and receiver components can introduce numerous challenges.

• Initially, manually assembled circuits tend to be larger. In IR receiving device scenarios, the circuit with an IR sender or receiver in an auto coupler configuration may experience interference from other IR signals.

• The enclosed design facilitates closed communication and shields the circuit from various factors, particularly temperature fluctuations.

• Notably, the manually crafted optocoupler operates at a lower voltage level than the PC817, underscoring the latter's advantages.

PC817 IC Optocoupler Circuit

The circuit diagram illustrating the PC817 IC Optocoupler is presented below. The IC, such as PC817, assumes a pivotal role in DC circuit switching within this configuration.

An integral component of the optocoupler above circuit is the Phototransistor, functioning akin to a conventional transistor switch. Employing an optocoupler-based, cost-effective phototransistor characterizes this circuit. Activation of the IR LED, controlled by switch 'S1', is pivotal.

Upon switch activation, the 9V battery supplies current to the LED through the 10K resistor. The intensity of the LED is modulated via resistor 'R1'. Lowering the resistance value amplifies LED intensity, consequently elevating transistor gain.

Conversely, on the circuit's other side, the phototransistor is responsive to the IR LED. When the LED emits IR light, the phototransistor establishes contact, setting the output voltage to '0'. Consequently, the connected load is deactivated.

As per the PC817 IC datasheet, it is imperative to note that the transistor's collector current is capped at 50mA. The 'R2' resistor configures the output voltage as 5V, acting as a pull-up resistor. In this circuit design, the optocoupler, employing a phototransistor, interfaces with a microcontroller for pulse detection or interruption.

While the operational principle of the PC817 optocoupler is straightforward, its integration with various devices necessitates adherence to distinct specifications. The input side mandates a current-limiting resistor for the optocoupler, while securing the logic output pin to the power pin is essential at the output. The generation of an infrared signal prompts a transition in the logic state from one to zero, attributable to the alteration in current flow.

Note: Optocouplers typically exhibit low output currents. For instance, the PC817 has a maximum output current of 50 mA. Consequently, a more than direct connection of high-current components, like motors, to the optocoupler output is needed. In these scenarios, including a transistor becomes imperative to provide the necessary current supply.

Test Circuit for Response Time

Test Circuit for Frequency Response

PC817 IC Equivalent

The replacement and equivalent of PC817 optocoupler include PC816, PC123, TLP621, TLP321, TLP421, PC17K1, H11A817, SFH615A, PS2501-1, PS2561-1, PS2571-1, LTV-816, LTV-817(-V), LTV123, LTV-610 K1010, K817P.

Alternatives Optocouplers

The alternatives of the PC817 optocoupler include MOC3021 (Zero Cross TRIAC) , MOC3041 (Non-Zero Cross TRIAC), FOD3180 (High-Speed MOSFET), MCT2E, and 4N25.

Where to Use PC817 IC

The PC817 Photocoupler incorporates a light-controlled (photon-based) transistor. This IC comprises an IR (infrared) LED and a phototransistor within its structure. When the IR LED is energized, the emitted light triggers the conduction of the transistor. The IR LED's and phototransistor's configuration and pinouts are illustrated below.

This IC establishes electrical isolation between two circuits; one segment of the circuit connects to the IR LED, while the other links to the phototransistor. The digital signal supplied to the IR LED is mirrored in the transistor's behavior, yet no direct electrical link exists between the two. This feature proves advantageous when isolating a noisy signal from your digital electronics. Therefore, if you are seeking an IC to facilitate optical isolation in your circuit design, the PC817 might be the ideal choice for your requirements.

How to use PC817 IC

Employing the PC817 IC is a relatively straightforward process. Connect the IR LED's anode pin (pin 1) to the isolated logic input, and link the cathode (pin 2) of the IR LED to the ground. Pull the transistor's collector pin high using a resistor (in this case, a 1K resistor), and connect the collector pin to the output of your desired logic circuit. Ground the Emitter (pin 4).

Important Note: Ensure that the ground line of the IR LED (pin 2) is not connected to the ground line of the transistor (pin 4). This non-connection is pivotal for achieving isolation.

When the logic input is low, the IR LED and transistor remain in the off state. Consequently, the logic output remains high, with the high voltage adjustable up to 30V (Collector-Emitter Voltage); in this instance, +5V is utilized. The 1K pull-up resistor serves as a load resistor.

Conversely, when the logic input is high (at least 1.25V, the Diode Forward voltage), the IR LED and phototransistor conduct, shorting the collector and emitter. Consequently, the logic output voltage becomes zero. This mechanism reflects the logic input at the output while maintaining isolation between the two. The comprehensive functioning can be visualized in the provided figure.

Another critical parameter to consider when utilizing an Optocoupler is the rise time (tr) and fall time (tf). The output does not transition instantaneously as the input logic changes states. The waveform illustrates the output's duration to transition from one state to another. For PC817, the rise time (TPDHL) and fall time (TPDLH) are 18us.

How do You Use it Safely in a Circuit for a Long Time?

For prolonged and secure operation of the PC817 optocoupler in your circuit, it is advisable to operate within the absolute maximum ratings consistently. Avoid exceeding a load of 50mA. The internal IR LED can be powered similarly to a standard LED, employing a current-limiting resistor. Therefore, always incorporate a current-limiting resistor at pin1 of the optocoupler, corresponding to the IR LED's anode or positive pin. Refrain from operating the device in temperatures below -30 degrees Celsius or above 100 degrees Celsius. Additionally, store it within the temperature range of -55 degrees Celsius to 125 degrees Celsius for optimal conditions.

PC817 Applications

The PC817 Optocoupler finds diverse applications in the following areas:

• Electrical isolation circuits

• Microcontroller I/O switching circuits

• Signal isolation

• Noise coupling circuits

• Isolation of digital from analog circuits

• AC/DC power control

• Reliability is a key attribute, ensuring dependable functionality.

• Signal transmission purposes

• Utilization in noise coupling circuits due to its capacity to mitigate noise factors

• Optocoupler is crucial in switching applications, effectively maintaining circuit continuity without disconnection.

• In-home appliances, the Optocoupler regulates AC loads by introducing frequency-induced pulses, enabling precise control within a defined range.

PC817 Examples: Arduino

The versatile application of optocouplers has expanded notably, particularly with the surge in IoT developments since 2012. These components are now integral in daily life, prominently in appliance control. In IoT, especially in domains like home automation and managing heavy loads, there is a need for precise control over AC loads through frequency modulation. Achieving this requires the implementation of a zero-cross mechanism.

Zero-crossing involves detecting alterations in the frequency signal of AC voltages, where the voltage changes provide the means to regulate AC loads. TRIACS play a pivotal role in further controlling the AC load.

In this context, the fundamental role of the optocoupler is to generate pulses that indicate changes in frequency. The optocoupler is connected to a rectifier via a high-wattage resistor. The rectifier transforms high AC to high DC, and the resistor reduces the DC voltage levels. While the DC voltage output is lower, it carries some noise, rendering it unsuitable as a clean signal. The optocoupler comes into play to convert this into a proper signal.

Operating through a rectifier, the optocoupler consistently produces a uniform pulse, irrespective of the noise in the signal. This singular pulse serves to identify instances of frequency change, commonly referred to as zero crossings. By detecting these zero crossings, microcontrollers gain the ability to control high AC loads through a straightforward microcontroller setup effectively.

220V AC Light Dimmer Example with PC817

To employ the dimmer, the utilization of a microcontroller is essential. Here, we will elucidate a technique for dimmer control using an Arduino.

Interfacing with Arduino

Presented below is the circuit:

The zero-cross pin will serve as the interrupt pin, and any digital pins can be employed to manipulate the signal. In the accompanying image, we delineate the pins for IR and dimmer, though it's important to note that these pins are not rigidly defined. The Arduino code to regulate the dimmer will be as follows:

Arduino Sketch

The provided code details the integration of zero-cross functionality with Arduino and outlines how Arduino can manage high-voltage control. This code is tailored for a single dimmer. Certain adjustments to the code will be necessary to extend its application for multiple dimmers.

Proteus Simulation

PC817 Package

2D-Model and Dimensions

PC817 vs EL817

	PC817	EL817
Input Diode Forward Voltage	1.25V	1.2V
Collector-Emitter Voltage	80V(max)	35V
Collector Current	50mA(max)	50mA(max)
Power Dissipation	200mW	200mW
Operating Temperature	-30°C~100°C	-55°C~110°C
Package / Case	4-DIP (0.300, 7.62mm)	4-DIP (0.300, 7.62mm)
Applications	Already mentioned in the above application section	Measurement Instruments Home Appliances Telecommunication Devices Programmable Controllers

PC817 Datasheet

Download PC817 Datasheet PDF.

Conclusion

This encompasses a brief overview of the PC817 Optocoupler or optoisolator datasheet. The heightened prevalence of the IoT field has rendered this IC highly advantageous, making it extensively employed for regulating diverse appliances in daily routines. Its utility extends to electronic circuit design scenarios where the potential for voltage surges or spikes threatens circuit components.

The primary function of this IC lies in circuit isolation, offering protection against voltage fluctuations. Moreover, it eliminates noise from signals, segregating low-voltage DC circuits from high-voltage AC circuits. Additionally, the IC plays a pivotal role in controlling AC voltage or larger voltage magnitudes using small analog or digital signals.

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