Relay Circuit Assignment - Job #1
Here are the tasks to complete for this assignment. You may want to print
this page. Check off each task when done. Then move on to the next task.
Definitions Before You Begin
Be sure you have an understanding of these terms before beginning this exercise.
You may need to use a dictionary, a code book, a theory book, or even ask other
electricians you may know for help. This is part of the learning activity. Begin
now.
terminology
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definition
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closed contacts
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open contacts
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jog
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run
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energize
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coil
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coil voltage
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limit switch
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contacts
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two wire control
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three wire control
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pushbutton
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normally open n.o.
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normally closed n.c.
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relay
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master switch
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VAC
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overload OL
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L1
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L2
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M magnetic Coil
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Read this
As background, here are some details which will help you understand this
assignment. If you encounter words, terms, phrases or abbreviations which you do
not understand, then stop. Research the meaning before going on. This is very
important to your learning activity. The essence of any technical education
activity is comprehensive understanding of all topics which are encountered.
Background Information
The momentary contact pushbutton shown in this diagram can be any set of
contacts. For example, the pushbutton could be replaced by a thermostat, a limit
switch, a door switch, or a light sensor. Then based on the condition
interpreted by the sensor, the coil could energize based on the position of the
contacts in the limit switch.
So instead of a person standing at a switch, the condition makes the
contacts close, or open. This condition could be heat, cold, light, dark, liquid
levels, pressure, pretty much any value that can be measured that can be
interpreted by a sensor.
The obvious advantage of this sort of control diagram is that the circuit
will work automatically with no human involvement needed.
An expanded version of this diagram is the double limit switch found in a
water tank. When water level falls to a preset level through use, the fill pump
comes on. Once a high water level limit is reached the pump goes off. All
automatically. Limit switches come in many types for various purposes.
This two wire control operates exclusively based on limit switches.
SOURCE
"Ladder" diagrams
Ladder diagrams are specialized schematics commonly used to document
industrial control logic systems. They are called "ladder" diagrams
because they resemble a ladder, with two vertical rails (supply power) and as
many "rungs" (horizontal lines) as there are control circuits to
represent. If we wanted to draw a simple ladder diagram showing a lamp that is
controlled by a hand switch, it would look like this:
The "L1" and "L2" designations
refer to the two poles of a 120 VAC supply, unless otherwise noted. L1
is the "hot" conductor, and L2 is the grounded
("neutral") conductor. These designations have nothing to do with
inductors, just to make things confusing. The actual transformer or generator
supplying power to this circuit is omitted for simplicity. In reality, the
circuit looks something like this:
Symbols
Click HERE
to see a page of standard electrical symbols used with relay circuits. Look them
over. Print a copy of the page for handy reference.
Go to the Diagram of this Job
Click HERE to go to the diagram, lecture, and picture for this exercise. Follow
the instructions found there. Then return to this page with your back button.
Review Electrical Safety Before Continuing
Always of concern to an electrician is electrical safety. Please review
the safety information provided at ElectricianEducation.com. Click HERE
to go to a collection of details which you can use as you prepare for the
assignments in this online course.
Of Special Note
Use a GFCI protected circuit for these exercises. Do not energize your test
circuits until you are sure of the connections. Have another working electrician
verify that you have done the work correctly before applying power to the test.
Then stay well clear of the uninsulated aspects of the circuit while power is
on. Remember to turn off power before making adjustments to the wiring. Click HERE
to read about GFCI protection.
Connect the Components
Use the material list on the diagrams page to have ready all the components you
will need to complete this exercise. Connect all required components based on
the diagram.
Check your Connections
With the diagram as a guide, verify that all the connections have been made
properly.
Apply Power To Test
Wear safety glasses when testing this circuit. Locate the overcurrent protective
device for the circuit you will use. If possible, connect to a GFCI protected
circuit for the added safety. Be sure you have a full understanding of this
circuit before applying power. Then when you test the circuit, there should be
no problem with it working properly. If there is a problem with correct
operation, turn the power off. Make corrections to the wiring as needed so
the circuit works properly. Then try the test again until the circuit
works properly. Memorize these connections.
Sketch the diagram from Memory
A sure way to determine if you have internalized this circuit is to draw a
sketch of the diagram from memory. You may choose to use a straight edge. But
that is not necessary. When you have completed the sketch, check it against the
diagram which is given for accuracy. Electricians must have the ability to
remember circuit connections without reference. Here is your chance to
demonstrate what you have learned. If you are unable to sketch the ladder
diagram from memory, refer back to the given ladder diagram. Then try again.
Repeat this activity until you feel confident that you can sketch this specific
diagram without reference.
Reconnect From Memory
Now on to the real test. Reconnect this diagramed circuit from memory. This will
ultimately tell you if you understand this circuit or not.
Review Before Answering Questions
Go back to review definitions, the diagram, the picture, your notes, your sketch
and any other details which will help you as you move on to the questions about
this diagram.
Answer the Questions
When you are satisfied that you can draw a sketch of the diagram, and wire it
all from memory, it is time to go on to answer questions about the diagram.
Click HERE to go to the questions.
Check Your Answers
When you have completed the questions, go on to check your answers. If you have
any which are different than the given answers, try to determine the reason. Go
back to the diagram. Research the question. Ask other electricians you may know.
But do all it takes to understand the correct answer to each question.
Click HERE to go to the answers.
Go On
When you can answer all questions without error, and strongly feel you
understand all answers, it is time to go on to the next assignment.
Click HERE to go on to the next assignment page.
If you would like to research any of these topics further, enter the search
term in this Google Search Box:
Use these Relay Circuit links to go to where you left off in
your online activities.
Job
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Assignment
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Diagram
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Lecture
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Picture
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Questions
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Answers
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