# Relay logic diagram examples diagram base website diagram

In Electrical and Electronics Engineeringwe use different types of drawings or diagrams to represent a certain electrical system or circuit. These electrical circuits are represented by lines to represent wires and symbols or icons to represent electrical and electronic components.

It helps in better understanding the connection between different components. Electricians rely on electrical floor plan which is also an electrical diagram for doing any building wiring. Engineers use various types of electrical drawings to highlight certain aspects of the system but the physical circuit and its function still remains the same.

Some of these electrical drawings or diagrams have been described below. A block diagram is a type of electrical drawing that represents the principle components of a complex system in the form of blocks interconnected by lines that represent their relation. It is the simplest form of electrical drawing as it only highlights the function of each component and provides the flow of process in the system.

Block diagram are easier to design and is the first stage in designing a complex circuit for any project.

### UML - Activity Diagrams

It lacks the information about the wiring and placement of individual components. It only represents the main components of the system and ignores any small components. This is why; electricians do not rely on block diagram. The following two examples of block diagram show an FM transmitter and a variable frequency driver VFD. This diagram shows the process of converting an audio signal into frequency modulated signal. It is pretty simple and easy to understand.

Each block process the signal and pass it to the next one. Practically, the FM transmitter does not look like this, because the block diagram omits the individual components.

This block diagram shows a 3 phase AC power supply conversion into a DC which is again converted into a controlled AC supply. It is quite a complicated process but this diagram simplifies the process into blocks for better understanding.

The block diagram provides an idea how the process is done by not delving too deep into the electrical terms but it is not enough to implement a circuit. Each block is a complicated circuit that can be explained using other drawing techniques described below. The schematic diagram of an electrical circuit shows the complete electrical connections between components using their symbols and lines. Unlike wiring diagram, it does not specify the real location of the components, the line between the components does not represent real distance between them.

One can easily troubleshoot certain schematic by applying electronic circuit theory. It is the most common type of electrical drawing and are mostly used in implementing electrical circuits by technician. Most engineering student rely of schematic diagram while developing various electrical projects. This is a schematic diagram of a voltage amplifier. It uses various symbols to represents the electrical components and the lines to represent the electrical connection between their terminals.

The practical circuit may vary in appearance but the electrical connection and its function will remain the same. Single Line diagram SLD or one-line diagram is the representation of an electrical circuit using a single line.As an introduction to ladder diagrams, consider the simple wiring diagram for an electrical circuit in Figure 1a. The diagram shows the circuit for switching on or off an electric motor. We can redraw this diagram in a different way, using two vertical lines to represent the input power rails and stringing the rest of the circuit between them.

Figure 1b shows the result. Both circuits have the switch in series with the motor and supplied with electrical power when the switch is closed.

## Logic Diagram Templates

With such a diagram the power supply for the circuits is always shown as two vertical lines with the rest of the circuit as horizontal lines. The power lines, or rails as they are often termed, are like the vertical sides of a ladder with the horizontal circuit lines like the rungs of the ladder. Circuit diagrams often show the relative physical location of the circuit components and how they are actually wired.

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With ladder diagrams no attempt is made to show the actual physical locations and the emphasis is on clearly showing how the control is exercised. Figure 2 see below shows an example of a ladder diagram for a circuit that is used to start and stop a motor using push buttons. In the normal state, push button 1 is open and push button 2 closed. When button 1 is pressed, the motor circuit is completed and the motor starts.

Also, the holding contacts wired in parallel with the motor close and remain closed as long as the motor is running. Thus when the push button 1 is released, the holding contacts maintain the circuit and hence the power to the motor. To stop the motor, button 2 is pressed. This disconnects the power to the motor and the holding contacts open. Thus when push button 2 is released, there is still no power to the motor.

A very commonly used method of programming PLCs is based on the use of ladder diagrams.

Visual Walkthrough of Schematic Diagram and Control Logic

Writing a program is then equivalent to drawing a switching circuit. The ladder diagram consists of two vertical lines representing the power rails. Circuits are connected as horizontal lines, i. The vertical lines of the diagram represent the power rails between which circuits are connected. The power flow is taken to be from the left-hand vertical across a rung.

The top rung is read from left to right.Activity diagram is another important diagram in UML to describe the dynamic aspects of the system. Activity diagram is basically a flowchart to represent the flow from one activity to another activity. The activity can be described as an operation of the system.

The control flow is drawn from one operation to another. This flow can be sequential, branched, or concurrent. Activity diagrams deal with all type of flow control by using different elements such as fork, join, etc.

The basic purposes of activity diagrams is similar to other four diagrams. It captures the dynamic behavior of the system. Other four diagrams are used to show the message flow from one object to another but activity diagram is used to show message flow from one activity to another. Activity is a particular operation of the system. Activity diagrams are not only used for visualizing the dynamic nature of a system, but they are also used to construct the executable system by using forward and reverse engineering techniques.

The only missing thing in the activity diagram is the message part. It does not show any message flow from one activity to another. Activity diagram is sometimes considered as the flowchart. Although the diagrams look like a flowchart, they are not. It shows different flows such as parallel, branched, concurrent, and single.

Activity diagrams are mainly used as a flowchart that consists of activities performed by the system. Activity diagrams are not exactly flowcharts as they have some additional capabilities. These additional capabilities include branching, parallel flow, swimlane, etc.

Before drawing an activity diagram, we must have a clear understanding about the elements used in activity diagram. The main element of an activity diagram is the activity itself. An activity is a function performed by the system. After identifying the activities, we need to understand how they are associated with constraints and conditions. Once the above-mentioned parameters are identified, we need to make a mental layout of the entire flow. This mental layout is then transformed into an activity diagram.

Following is an example of an activity diagram for order management system. In the diagram, four activities are identified which are associated with conditions. One important point should be clearly understood that an activity diagram cannot be exactly matched with the code. The activity diagram is made to understand the flow of activities and is mainly used by the business users. After receiving the order request, condition checks are performed to check if it is normal or special order.

After the type of order is identified, dispatch activity is performed and that is marked as the termination of the process. The basic usage of activity diagram is similar to other four UML diagrams. The specific usage is to model the control flow from one activity to another. This control flow does not include messages. Activity diagram is suitable for modeling the activity flow of the system.

An application can have multiple systems.

Activity diagram also captures these systems and describes the flow from one system to another. This specific usage is not available in other diagrams.Relay logic basically consists of relays wired up in a particular fashion to perform the desired switching operations. The circuit incorporates relays along with other components such as switches, motors, timers, actuators, contactors etc. Relay act as switch which is operated by a small amount of current.

The relay has two contacts. In the figure given below, you can see there are two sides of a Relay. One is primary coil which acts as a electromagnet on passing current through it and other one is secondary side having NO and NC contacts. When the contact position is Normally Openthe switch is Open and hence the circuit is Open and no current flows through the circuit. When the contact position is Normally Closethe switch is closed and the circuit is completed and hence current flows through the circuit.

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This change of state in the contacts occur whenever a small electrical signal is applied i. Above figure shows the switch in NO contact position. In this figure, primary circuit coil is not completed and hence no current flows through the electromagnetic coil in that circuit. Therefore, the connected bulb remains off as the relay contact remains open. Now the above figure shows the switch in NC contact position.

In this figure, primary circuit coil is closed, so there is some current through the coil connected in that circuit. Due to the current flowing in this electromagnetic coil, a magnetic field is created in its vicinity and due this magnetic field, the relay is energised and hence closes its contacts.

Therefore, the connected bulb turns ON. You can find the detailed article on Relay here and learn how relay can be used any circuit. A relay logic circuit is a schematic diagram which shows various components, their connections, inputs as well as outputs in a particular fashion.

It contains two vertical lines, one on the extreme left and the other on the extreme right. These vertical lines are called rails. The extreme left rail is at the supply voltage potential and is used as an input rail. The extreme right rail is at zero potential and is used as the output rail.

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Particular symbols are used in relay logic circuits to represent different circuit components. Some of the most common and widely used symbols are given below.

The given symbol indicates a Normally Open contact. If the contact is Normally open, it would not allow any current to pass through it and hence there will be an Open circuit at this contact. This symbol is used to indicate Normally Close contact. This allows the current to pass through it and acts as a short circuit. This push button allows current to flow through it to the rest of the circuit as long as it is pressed.Creating Relay Logic Diagrams.

Recommend Documents. Central Locking Relay Configuration Diagrams GY etc are all wire colours found in Dynamco's relay sockets. Page 2. Creating diagrams for chess problems.

For problems issued in feenschach you may specify a period of months like Creating diagrams for chess problems - TeXdoc. Schwalbe you will Master of Philosophy in Physics. Assume a ladder logic diagram that consists of a list of rungs Ri. A railway yard is built from objects such as points, signals, track circuits, and. Creating and Using a Programmable Logic Aug 18, - Laboratory in the Computer Engineering Course By using programmable devices in the digital systems design course, we could Creating Program Logic Models - Sage Publications When well developed, they can ensure intellectual rigor for program logic Regular contribution Detecting races in Relay Ladder Logic programs.

Electromechanical relay logic This worksheet and all related files Design of industrial automated systems via relay ladder logic.

Four practice LSAT Logic Games with full explanations and diagrams the games under timed conditions, allow 35 minutes for all four or just under Figure displays a simple example of a relay logic diagram that. This sample chapter is for review purposes only. All rights reserved. This program defines the operation to be performed by the PLC. Rung: Horizontal line in a relay logic diagram that has input devices and an output device.The schematic diagrams for relay logic circuits are often called line diagrams, because the inputs and outputs are essentially drawn in a series of lines.

A relay logic circuit is an electrical network consisting of lines, or rungs, in which each line or rung must have continuity to enable the output device. A typical circuit consists of a number of rungs, with each rung controlling an output. This output is controlled by a combination of input or output conditions, such as input switches and control relays. The conditions that represent the inputs are connected in series, parallel, or series-parallel to obtain the logic required to drive the output.

The relay logic circuit forms an electrical schematic diagram for the control of input and output devices. Relay logic diagrams represent the physical interconnection of devices.

Each rung would have a unique identifying reference number and the individual wires on that rung would have wire numbers as a derivative of the rung number. Thus, if a rung was labelled asthe first independent wire would bethe second asand so forth. A wire would be named for the top most rung to which it connected, even if it branched to lower rungs. When designing a system, it was common practice to skip numbers for the rungs to allow later additions as required.

When the rack was manufactured, as a wire was installed, each end would be marked with wire labels a.

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This also applied for pulling wire into the factory through conduit or in trays where each wire would have corresponding numbers. Wire labels were typically pieces of white tape with numbers or letters printed onto them and collected in small, pocket sized booklets.

A number strip would be peeled out and wrapped around the wire near the end. Wire numbers were made up of a series of the number strips so wire would be four strips. There are also pocket sized printers that print onto an adhesive backed label that can be wrapped around the wire. Figure 1 shows a typical relay logic diagram. When the START button is pressed, the control relay energizes and its associated contacts change state.

In many cases, it is possible to design a relay logic diagram directly from the narrative description of a control event sequence. Draw a sketch of the operation process. Make sure all the components of the system are present in the drawing. Determine the sequence of operations to be performed.

List the sequence of operational steps in as much detail as possible. Write out the sequence in sentences, or put them in table form. Logic Gates Truth tables. Relay Noise in PLC. Nameplate Ratings. Trip Logic using PLC. Save my name, email, and website in this browser for the next time I comment.

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More.I believe this is because students must learn several pieces of information and then weave them all together in order to truly understand electrical diagrams.

Understanding basic circuits is also a must. Students should be able to construct basic circuits consisting of loads and switches. Finally, they must have a good concept of how the system they are working on heats or cools.

If all this is in place they usually will have no problem learning how to read electrical diagrams. I find that students who are the weakest with diagrams are usually also weak in one or more of these foundation areas. After all, a diagram is simply a representation of a collection of circuits that are made up of electrical components. So we start by having students build basic circuits with switches and lights in order to learn how loads and switches work in a basic circuit.

Loads should have a voltage drop when current passes through them, switches should not. Then we introduce components and relate them to either loads or switches.

So thermostats are switches while motors are loads. Introduce symbols and have students draw symbols for selected components. Then have them identify components on a unit using the unit diagram.

The most difficult components for students to grasp are usually contactors and relays. Understanding relays is a big stumbling point for many students.

I have a method for teaching relays, but I will save that for another article.

### Diagram Templates and Examples

Just know that there is no use trying to explain a ladder diagram that contains 24 volt control relays to someone that does not understand how relays work. After explaining basic ladder diagrams and showing several examples ask the students to draw a simple diagram of a packages air conditioning unit without looking at an example.

There will be lots of weeping and gnashing of teeth. Students will complain that they are not artists and that drawing diagrams is not necessary to service systems. However, you will find out quickly how much they understand about circuits, components, and diagrams.

## What is Relay Logic ?

People that understand diagrams can draw them. Be patient, suggest corrections, and have them revise their diagrams until they have something that will work. This typically takes several revisions for many students. Finally, have them wire the circuit that they drew using the actual components as much as possible.

For safety we have a simple rule: the instructor has to check the circuit before it is energized. The pride the students get from seeing their circuit operate will offset the anguish they experienced getting there.

Gradually add more complex circuits — two stage cooling, cooling and heating, heat pumps, or whatever makes sense for your area. There are as many variations as there are manufacturers, adding to the difficulty for aspiring technicians. Post a Comment. Friday, June 4, Teaching Ladder Diagrams.