# Traffic Light in Multisim using PLC

Written by Larsha Johnson
9/27/2021

Programmable Logic Devices (PLDs) are integrated circuits that contain a relatively small number of functional elements that provide user-configurable logic functions (AND, OR, etc.)
In Multisim a PLD schematic contains specialized components that define the operation of the individual logic blocks of the PLD.

What is PLC and PLD?

The biggest difference between the two is the control logic. PLC is a fixed logic device (the function is realized by changing the software), and PLD is a variable logic device (the function is realized by changing the internal circuit structure).

The concepts of PLC and PLD can be practiced through this two-way traffic light example. The main implementation of traffic light signals in to avoid traffic jams and serves the purpose of avoiding vehicular collisions.

The ladder diagram in this blog runs two traffic lights. The ladder diagram is contained in a separate hierarchical block called TrafficLightLogic

There are two different traffic light examples available, look in the sample circuit "blue folder icon" in the Educational version of Multisim that implements a traffic light:

1. National Instruments\Circuit Design Suite 14.2\samples\Educational Sample Circuits\Ladder Diagrams
2. National Instruments\Circuit Design Suite 14.2\samples\PLD Sample Circuits

The first choice uses programmable ladder logic with an actual traffic light simulation. For choice two, you can export the sample to program the NI Digital Electronics FPGA Board.

Drag n drop these snippets directly into your Multisim workspace

*I also attached a short version of the NI Multisim for Education PDF specifically for traffic light designs.

What is an SNIPPET file? Section of programming code saved in XML format; code snippets can be saved from Visual Basic, Visual C#, and Visual J projects; they can be edited using the Code Snippet Editor and managed using the Code Snippets Manager.

Find the attached files below. Hope this helps!

This topic refers to education-specific features of Multisim.

## Saturday, September 25, 2021

### MATLAB - Family of Curves (Vectorization)

#### MATLAB Techniques

Written by Larsha Johnson
9/25/2021

Linear Signals and System, matrix operation fundamentals. This example illustrates a techniques called vectorization. Algorithm vectorization uses matrix and vector operations to avoid manual repetition and loop structures. With simultaneous creation of curves one can maximize the use of matrix applications.
The result here is a 201 x 11 matrix with identical columns.

%% Matrix Operations - Family of Curves
r = [1 0 0]
A = [2 3;4 5;0 6]
c = r' B = [c A]
B(1,2)
B(1:2,2:3)
B(2,:)
A = [1 -2 3;-sqrt(3) 1 -sqrt(5);3 -sqrt(7) 1];
y = [1;pi;exp(1)];
x = inv(A)*y x1 = det([y,A(:,2:3)])/det(A) alpha = (0:10);
t = (0:0.001:0.2)';
T = t*ones(1,11);
H = exp(-T*diag(alpha)).*sin(2*pi*10*T+pi/6);
plot(t,H); xlabel('t'); ylabel('h(t)');
[R,P,K] = residue(B,A)
[R,P,K] = residue([1 0 0 0 0 pi],[1 -sqrt(8) 0 sqrt(32) -4]);
R.', P.', K title('Family of Curves - Vectorization')

Try this code out to graph this figure! Modify freely and comment on this post if it helps. Thanks for reading.

## Saturday, September 18, 2021

### Create a Logic Circuit in NI Multisim - Snippet

Written by Larsha Johnson
9/18/2021

### Software

• Multisim

In Linear Control Systems Lab the topic of programmable logic controllers was introduced. There is a variety of software available on the web to try PLC yourself, in this blog I used NI Multisim 14.2

๐Before arriving to this blog you may have asked yourself...how do I implement a logic circuit using ladders within the Multisim environment? Is there any way to learn about ladder logic using a simulated circuit environment such as Multisim?

The Education edition of Multisim lets you capture and simulate Ladder Diagrams. These diagrams are electrically based, as opposed to the binary/digital representations employed by ladder logic. Diagrams of this type are used extensively for industrial motor control circuits.

Ladder Diagrams are able to drive output devices or take input data from regular schematics and embed the instructions on how input states affect output states in either the same schematic or separate hierarchical blocks or subcircuits that contain the Ladder Diagram.

Note: Refer to the Multisim User Guide for a complete description of hierarchical blocks and subcircuits.

๐An example of how to create this ladder logic in Multisim is as follows:

The cursor appears with the rung’s left and right terminators attached.

2. Click to place the first rung and continue clicking and placing until you have placed four rungs as shown below. Right-click to stop placing rungs.

๐To add components to the rungs:
1. Select Place/Component, navigate to the Normally Open Relay Contact
(RELAY_CONTACT_NO) click OK.

Note: This device is found in the Ladder Diagrams Group - Ladder Contacts Family.

2. Drop the relay contact directly onto the first rung.

3. Continue in this manner until all relay contacts have been placed. (X4 must be placed and
then wired separately).

4. Place the lamps (Group - Indicators; Family - Lamp).

5. Place relay coils M1 and M2 on the third and fourth rungs (Group - Ladder Diagrams;

6. Place switches J1 and J2.
7. Double-click on each switch, select the Value tab, and change the key for J1 to 1 and the
key for J2 to 2.

๐To change the controlling device reference for X2 and X4:
1. Double-click on X2 and click the Value tab.
2. Enter M2 in the Controlling Device Reference field and click OK. Repeat for X4. The completed Ladder Diagram appears as shown below.

Embed the circuit file within a PNG image file using a Multisim Snippet and let your peers drag and drop the circuit into Multisim instead. This tutorial explores the new technology and ways to take advantage of it.

๐ Please try our snippet out for yourself and practice designing logic gates own your own.

Sharing Multisim circuit files has never been easier. You can now see a graphical preview of the circuit design before opening, and you no longer need to attach and save files on supported web browsers. This saves you valuable time and increases your productivity.

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