How to Test almost all kinds of Optocouplers ?

Optocoupler Tester

An optocoupler tester The purpose of an optocoupler is to transfer signals from one circuit to another yet keep them galvanically isolated.
in this post i want to show you how to check if an optocoupler is working. This circuit requires only a 12 volts power supply .

Components : 

• 1x 7805 voltage regulator 
• 2x 1kΩ resistor  
• 1x 470Ω resistor 
• 1x 120Ω resistor 
• 1x 2N3904 transistor (or any  general purpose transistor will work) 
• 1x 1N4007 diode 
• 1x relay
• an LED 

How to correctly place an optocoupler  : 

In the picture shown you will find a dot in the component package  indicating the correct orientation of the package , usually this is indicated in the datasheet of the component , but i thought that you should know this any way.

Why this circuit ?  

Now there are several way to test an optocoupler, but this circuit in particular will allow you to test a lot of them much faster , and by including the right mount in your pcb you can test a variety of packages including smd packages  ,

Working of the circuit : 

This circuit will take a 12v voltage source and then step it down to 5 volts using a 7805 linear voltage regulator as well as providing a 12v source to the 12vDC relay. the transistor will act as a switch and turn on/off according to the optocoupler's output voltage thus will result in an electromagnetic field in the relay's core and eventually a closed circuit of the relay output  and the led turning on. 

Conclusion: 

There are a lot of possible configurations to this circuit depending on the kind of optocoupler that you are willing to use come optocouplers require a 3.3 v source you should check the specified datasheet first and get the exact ratings of your component .