advantages of Relay Cards ?

[ameen01]

Hello,

I would like to know why relay cards are used. What are the advantages. I have an application where they use relay cards at the output module of PLC . Please guide me with this

 

[BradtheRad]

I've seen relay card projects in catalogs. Never got one. They look more expensive than they need to be.

But sometimes you need one. The card has components which make it possible, or make it safe, to drive relay coils when the source is weak or delicate.

Your computer port, etc., may be unable to provide the voltage (or current, or both) to energize a relay coil. Or there is risk of overloading components inside the computer.

To be safe you use a relay card.

It consists of middleman components that require only a small signal. Often all that's required is one trasistor or mosfet to drive the relay.

The middleman component draws from an external power supply to drive the relay coils. You have to provide the external power supply.

A relay card can have several such units. Useful for things like operating household lights, appliances, robotics, etc.