ECD302

Miscellaneous Simulation Tools

Miscellaneous Simulation Tools

555 timer wizardFilter wizardCE BJT Amplifier wizardComponent tolerantCreating Sub-circuitsPost processing

555 timer wizard

Use the 555 Timer Wizard to build astable and monostable oscillator circuits that use the 555 timer

Two types:

•Astable Operation

•Monostable Operation

555 timer wizardSource voltage

Astable Operation-produces a free-running oscillator that does not need any input signal.

555 timer wizard

555 timer wizard

Monostable Operation-produces a single output pulse in response to an input trigger pulse. When an input signal is applied, each input pulse will produce one output pulse.

555 timer wizard

Filter wizard

The Multisim Filter Wizard lets you design numerous types of filters by entering the specifications into its fields.

Filter wizardLow pass filterHigh pass filterBand pass filterBand reject filter

Filter wizardLow pass filter

At high frequency, the output starts to drop to stop.

Filter wizardHigh pass filter

Low pass filterHigh pass filterBand pass filterBand reject filter

Filter wizardHigh pass filter

At low frequency, the still low output.

CE BJT Amplifier wizard

Wizard lets you design common emitter amplifier circuits by entering the desired specifications into its fields. The designed circuit can then be verified by SPICE simulation directly.

CE BJT Amplifier wizard

Component Tolerance

When the output of your circuit is slightly different from theoretically prediction, do not be too quick to blame the component tolerance.In MultiSIM, the component tolerance is DISABLED, by default. This means, by default, all your component values are simulated “exactly as is”. No tolerance.

How to know it is DISABLED?

As shown here:

When enabled, there will be a “tick” here.

When it is ENABLED…

You will see the option selected:

The “tick”.

With tolerance disabled…

In this example, the component tolerance is disabled. You should get the same resistance reading from all meters:

Filename:L4_cct01.msm

Enabling component tolerance…

You will be prompted with this screen. Just set the percentage of tolerance you want, and click “OK”…

Only this field is editable because our circuit has only resistors…

With tolerance enabled…

You should now see the component values all different…

All the set values are still 1 k…

…but all the component values are now different.

Virtual vs. Real components

Now, perhaps you have noticed that the component tolerance seems to be applicable only to VIRTUAL components… what about REAL components?

Does this mean that REAL components have no tolerance?

Real components, tolerance disabled…

Of course, there is no tolerance…

Filename:L4_cct02.msm

Real components, tolerance enabled…

There is no tolerance either! So, we can see that REAL components in MultiSIM are not subjected to tolerance.

Creating Sub-Circuits

When designs get HUGE, it is always a good practice to manage your circuits in smaller “chunks”.Such practice is especially useful when your design has multiple parts of the same circuit patterns. We will look at an example in the following slides.

A 2-stage Common Emitter Amplifier

Filename:L4_cct03.msm

Repeated design pattern

You can see that the 2 stages of common-emitter amplifiers are actually the same.

Creating a Sub-Circuit

We will copy this part into a new file, and add to it some input/output terminals to save it as a sub-circuit file.

Filename:L4_cct04.msm

Using the sub-circuit

Whenever you need to use the sub-circuit, open the file, copy the whole circuit, then open a new document (or an existing document where you want this sub-circuit to be added to). Select all and copy.

Pasting as sub-circuit

In the new document (or existing document you want to add the sub-circuit to), just click on any empty space on the design sheet, then choose to “paste as subcircuit”.

Naming sub-circuit

Paste the sub-circuit twice, to get the two stages. Name your two stages differently.

You should get this:

Just use it!

Make similar connections as the earlier circuit:

Filename:L4_cct06.msm

Results comparison

You can see from the oscilloscope displays below that the full circuit and the circuit with sub-circuit function exactly the same:

From L4_cct03.msm From L4_cct05.msm

Post-Processing

Post-processing makes up for what analysis is lacking in the MultiSIM package.It basically takes the results of other analyses to produce a derived set of results according to formulae specified by the user.

Instantaneous Dissipation of Power

For example, MultiSIM does have a wattmeter, but it measures the RMS power, and furthermore, the time-varying results are not recorded. If we wish to record instantaneous power dissipated in a component as time varies, we would find the wattmeter incapable of doing that.

Post-Processing to the rescue!

To make up for that lacking, we could actually use the post-processing capability of MultiSIM to do what we want.The process of doing so will be illustrated in the following slides.

Example

Let us use an example of series RLC circuit, as shown below, from which we wish to find the instantaneous power in the resistor:

Filename:L4_cct08.msm

The process before the “post” process…

Before we could use the post-processing capability, there must be some prior results from which the post-process could derive the required data.For finding power, we could use the formula: P = V2/R. So, we should at first measure the instantaneous voltage across the resistor.

Transient Analysis to get the voltage across the resistor…

The voltage across the resistor could be measured using the transient analysis, where we would set the output variable as “voltage at node 3”, as shown below:

Other settings…

We should also set the start and stop time for the transient analysis. With the input frequency being 100 kHz, simulating for 0.1 ms should be enough to get us results over 10 cycles:

Set the stop time as 0.1 ms after starting.

Data

The results are displayed – and stored until program shutdown – in the grapher, as shown here:

Invoking the Post-Process

After obtaining the data for instantaneous voltage, we can now invoke the post-process (look under “Simulate” from the menu).

Put in the required formula. R1 is 1 k, hence the 1000.

Highlight the name of the previous analysis from which you wish to derive the data.

Variable(s) available in the previous analysis that you have specified in the field to the left of this.

Mathematical functions that you may use in the post-process.

Further settings…

Upon clicking “new trace”, you will be prompted for the name of the page; just click “OK”:

Further settings…

Then you will be prompted for the name of the graph. Rename or just click “OK”:

Then click “Draw” to draw the graph according to the formula you specified:

This graph indicates the instantaneous power dissipated in the resistor due to the AC input.

Exporting Data to MS Excel

You could also export the results of your analyses to MS Excel for external processing (if you find the post-processing capability not up to par for the further analyses that you want).

Exporting Data…

It is as easy as just clicking from the menu the “export to Excel” function:

You will get two columns of data in MS Excel:

The first column is the data for “time”, as our results were simulated against time.

The second column is the data, in this case, the instantaneous power dissipated in the resistor R1.

Limitation of Data Export

It should be noted, however, that at any one time, you can only export ONE set of data (that is, one column of time, and another column of the currently active trace).If your graph has more than one trace of data, only the currently active (selected) trace will be exported.