DIGITAL ELECTRONICS Homework / LAB / Multisim

ELEC201 Digital Electronics

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Excelsior College

Module 1: Laboratory1: Introduction to MultiSim

Objectives

The objectives of this experiment are to:

 Learn how to open, modify, and save a circuit file.

 Demonstrate interactive simulation capabilities.

 Understand how to find things in MultiSim.

 Install all circuit files for the laboratory.

Introduction

This experiment is designed to introduce MultiSim to a novice.

MultiSim is a complete electronics lab inside the computer. Using only simple mouse

movements (or keyboard commands) you can set up an analog or a digital circuit (or a mixture of

both), simulate its operation, make measurements with virtual instruments, and never worry

about hooking up something wrong and causing damage.

The procedure is designed to have you work your way through a simple circuit. It is assumed that

you know the following:

 How to navigate around directories.

 How to use the mouse inside Windows.

Procedure

1. Install MultiSim. After installation, you may need to register your software to obtain a release code, or the software stops working in 14 days. Read the documentation that

comes with MultiSim. The Getting Started document is helpful during installation. In this

lab and all others, there will be one or more MultiSim circuit files for you to open and

work with. You may download them individually as you do the experiments and unzip

them into the directory of your choice.

2. Start up MultiSim. You will see a window similar to that shown in Figure 2.1.

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Figure 2.1: MultiSim startup screen: Some of the critical portions of the screen are

indicated.

3. Load the circuit E2-1.MS7, shown in Figure 2.2. This is accomplished by left-clicking on the ‘File’ menu and then left-clicking on the ‘Open’ option. You will get a list of

MultiSim MS7 circuit files. If you are not in the proper directory, navigate to it and then

double-click on the circuit file E2-1.MS7 to open it.

Figure 2.2: Sample circuit

4. To determine if the circuit is operating correctly, let us examine the state of the NAND gate output. You can use the logic indicator from the ‘Indicators’ parts bin. Do this by

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clicking on the icon for the ‘Indicators’ bin ( ). A window with various parts should

open next to the workspace, as shown in Figure 2.3.

Figure 2.3: Indicators parts bin

5. To place a logic indicator (a Probe), click the desired component, then click OK. The component will attach itself to the mouse pointer. The component will be placed

wherever you click the mouse within the circuit. Your circuit should now look like Figure

2.4.

Figure 2.4: Adding a logic indicator

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6. To connect the logic indicator to the F output, move the mouse pointer until it is near the round connection node labeled F. When you get close enough a small black dot will

appear, indicating that you are starting to place a wire. Left-click on the black dot. As you

move the mouse, a thin black ‘wire’ should appear between the black dot and the mouse

pointer. Move the mouse pointer close to the wire coming out of the logic indicator.

When you get close, another black dot will appear. Release the mouse button to make the

connection. You should now see something similar to Figure 2.5.

Figure 2.5: Connecting the logic indicator

If you decide in the middle of placing a wire that you do not want to finish placing it,

simply right click and the wire will vanish.

The logic indicator is used instead of a LED, which requires additional time to be

simulated properly. Before you connect the logic indicator, you can rotate it around to get

the connection lead where you want it. Use Control-R to rotate any selected component.

A component is selected by a single left-click.

7. Turn the circuit on by left-clicking on the power switch. The logic indicator should glow, indicating a logic one level. Congratulations! You have correctly installed a logic

indicator. Note that the indicator may also glow red, green, or blue, depending on which

one is chosen.

8. The switch labeled A is controlled by pressing the A key. Each key press moves the switch to its opposite position. The 4.7 K ohm resistor is used to create a logic one level

on the output of the switch. The ground connection is for making a logic zero. Press the

A key a number of times. Does the logic indicator turn on and off?

9. Now modify the circuit by adding an inverter on the output of the NAND gate. It is necessary to delete the wire from the NAND gate output to the F node. Move the mouse

pointer over the wire. Left click once to select the wire. Then press Delete. You should

see something similar to Figure 2.6 now.

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Figure 2.6: The output wire has been removed

10. Grab a second inverter from the Logic Gates bin. Select the 7404. Choose one of the six sections A-F, place it between the NAND gate and the output node, and connect it. Figure

2.7 shows the final circuit.

Figure 2.7: Final test circuit

11. Test the new circuit to verify its operation.

12. Once a component has been placed and connected, it is often necessary to change its value. To change the value of either 4.7 K ohm resistor, double-click on it, or single-click

to select it and then go to the ‘Edit’ menu and select the ‘Properties’ option. A resistor

dialog box appears (see Figure 2.8) that allows you to enter the new resistor value. Enter

2.7 and be sure ‘K ohms’ is also indicated. Then click on ‘OK.’

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Figure 2.8: Changing the resistor value

The same method can be used to change the keyboard key that controls the switch.

13. To save the new circuit, go to the ‘File’ menu and select the ‘Save’ or ‘Save as…’ option. ‘Save’ is usually used to simply update the current circuit file (a warning is issued that

allows you to cancel the Save operation if necessary). “Save as…’ is used to save the file

under a different name.

14. Circuits do not always work the first time we set them up. Things get overlooked or connected differently than expected. Troubleshooting your circuits will be valuable

experience. You must develop your own skills as a troubleshooter, but these tips should

come in handy:

Is everything connected to power and ground?

Are you using the instrument the right way?

Are all component values correct?

Are there any shorts or opens?

Have you clicked the Power switch to start the simulation?

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Discussion

While reviewing your data and results, provide detailed answers to each of the following:

1. How is a parts bin selected?

2. How is a component selected?

3. How are wires added to the circuit?

4. When is the circuit simulated?

5. Will the computer burst into flames if your circuit is connected wrong?