Introduction
In this tutorial lets find out how to design a relay circuit with an isolated input . Isolated method provide a extra layer of protection to your circuit. The reason behind the design of this circuit is to protect the control circuit from any back EMF from the relay circuit . This circuit can be customized and designed for your own specifications. This is a basic concept that can be customized for your design.If you are designing a sensitive or device with expensive components this is how it should be done.
Isolated Relay PCB
PCB isolated relay module
This is the PCB design of this circuit . It’s a two layer PCB with the thickness of 1mm.The PCB has two sections . One is the AC side the other is the DC side both are separated in the PCB design to prevent any damage in case of a leak. You can upload this files directly to a PCB manufacturing site such as JLPCB and made your own PCB . The zip file include Gerber file , BOM file and Pick and place file . You can download the file form HERE !
Final Thoughts
This circuit can provide protection by isolating the input from the relay output.Although , This is a relay output circuit. You can use this design to other switching methods as well (FET , BJT) .Design changes should be made while keeping the component specifications in mind.
Pros and Cons
When considering the components used for this design. there are few components added to provide the isolation . If your design doesn’t have isolation you have a design without a Opt coupler. Hence , less components and more PCB area can be saved .However the protection isolation will provide is more impotent than saving few bucks when it comes to long run.