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Opto-Coupler Tester

The document describes a simple optocoupler tester circuit designed to check the functionality of a PC817 optocoupler. It details the components, including the optocoupler pins, resistors, a switch, and an LED, as well as the working principle involving the activation of the internal LED and phototransistor. If the external LED lights up when the switch is pressed, the optocoupler is functioning correctly; otherwise, it may be faulty.

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282 views2 pages

Opto-Coupler Tester

The document describes a simple optocoupler tester circuit designed to check the functionality of a PC817 optocoupler. It details the components, including the optocoupler pins, resistors, a switch, and an LED, as well as the working principle involving the activation of the internal LED and phototransistor. If the external LED lights up when the switch is pressed, the optocoupler is functioning correctly; otherwise, it may be faulty.

Uploaded by

SUDHARMA99
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Opto-Coupler Tester

The image above shows a simple optocoupler tester circuit. It is designed to check whether an
optocoupler (in this case, a PC817) is functioning properly. Here's a breakdown of the components and
how the circuit works:

Components:

Optocoupler PC817: The main component being tested. It has 4 pins:

Pin 1: Anode (A) of the internal LED

Pin 2: Cathode (K) of the internal LED

Pin 3: Emitter (E) of the internal phototransistor

Pin 4: Collector (C) of the internal phototransistor

330Ω resistors: Limit the current through the LED inside the optocoupler and the external LED.

Switch: Allows you to turn the input LED on and off manually.

LED (3V): Lights up when the optocoupler works correctly.

5V DC Power Supply

Working Principle:

1. When the switch is pressed, 5V is applied through a 330Ω resistor to the internal LED of the
optocoupler (between pins 1 and 2). This causes the internal LED to emit infrared light.

2. The light activates the phototransistor inside the optocoupler (between pins 4 and 3), allowing current
to flow from pin 4 to pin 3.

3. This turns on the external LED (connected to pin 4 through a 330Ω resistor to 5V), indicating that the
optocoupler is working.
If the LED lights up when the switch is pressed, the optocoupler is functioning correctly. If it doesn't, the
optocoupler might be faulty.

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