Today we gone talk about how relays work .it’s relatively easy for anyone with an understanding of relay type control to program PLCs with little guidance.
Some of you must have already used relays
relays are used in our day to day devices like refrigerators, washing machines heaters and air conditioning.
The earliest application of relays started during long distance telegraphy there when you pressed and released a letter to type and interrupted the current flow.
The signals traveled through IO from transmitter to receiver.
Your two pulses, turn the electromagnet on and off, pulling and releasing a level, a pencil.
At the bottom of the level recorded the code on a moving paper.
Relay Working Principle or Relay Operation
In fact, some of the first computers ever will use relays to implement Boolean gates, as we can see from the applications are really is used mostly as a switch.
But do you know that relays operate on a low power, and can be used to control a circuit of very high power.
Let’s simplify relays are really consist of two separate and completely independent circuits.
One is called control circuit, and another is called load circuit.
One circuit drives, another circuit.
Let’s understand the components that make a really electromagnet armature and spring.
Let’s first understand an electromagnet.
We take a metal rod and wind, a conductive wire.
Usually insulated copper around it.
It is powered using a battery.
We know that an electric currents has the ability to produce magnetic field in a plane perpendicular to the direction of current flow
the electromagnet uses this principle, current is introduced, only when the switch is closed. When current flows. It energizes the coil and creates a magnetic field electromagnets are useful, because you can turn the magnet on and off by completing or interrupting the circuit.
Let’s see, the armature. There is a magnetic object, the electromagnet for the purpose of making it move.
When the coil is energized with electric current, the armature acts as a switch to complete the Second Circuit,
when current runs through the control circuit and energizes the coil. It creates a small magnetic field, which pulls off the switch, towards the coil and completes the Second Circuit.
Test the light glows. When the electromagnet is not energized, the spring pulls the armature away, and the socket does not complete the lightest of these parts are held safely.
With the help of a spring, the relay coil may only consume fractions of power. While the load circuit may be able to conduct hundreds of times that amount of power to a load, in effect, really acts as an amplifier relays are often used for isolating one voltage level from another.
This is why relays are used to safely control heavy load circuit.
When you use relays, you have to decide whether it should work as normally open or normally closed
normally open or normally closed relays depend upon the configuration of armature.
In the example that we have shown. This is an example of normally open relay
The normally closed really looks this way, the armature is placed in such a way that the load circuit is completed.
When the contact switch is turned off.
When you develop a PLC program, you will be using relay logic. but instead of hardware logic with actuators.
You will now have ladder logic contacts or Boolean instructions. Just like the input actuators. You have both normally open and normally closed contacts available in PLCs programming.
Often they are referred as examine is closed and examine is open. In the next article we will talk about it more.
Please write comment below if you have any questions about relay logic