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Advices for the new SIMetrix users.
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Advices for the new SIMetrix/SIMPLIX Intro users.

Posted 4th March 2012 at 06:37 AM by Alain Poitras
Updated 16th March 2012 at 02:36 AM by Alain Poitras


I am a steady user of the SIMetrix/SIMPLIS Intro Spice simulator and many peoples ask me how to use it. Because the same questions come back all the times and the answers often need to be quite elaborate and are time consuming, I decided to open a new Blog for this subject.

Since I am a member of this forum, I noticed there was thousands of threads and they often get loss very far from the first page after few days, where almost nobody can see them.

This is not the case with the blogs because there is not many yet on this site, also, it is possible to edit a blog anytime and not a post in a thread after 30 minutes ... This make corrections easy and I am not perfect, I often make some little or big mistakes.

I will not accept other members comments until the blog is almost terminated. Anybody having a request or a comment for me about this blog can send me private message, I will be glad to answer it and update my blog if this is necessary.

Of course, it will take me time to elaborate the texts and produce the associated graphics and schematics, so I will add them gradually from now.

SIMetrix/SIMPLIS Intro is a very fast and powerful simulator, also a friendly user software, but it can take a lot of times to learn how to use all is basic functions because there are so many. I write this blog to share my own experience with the others users.

The demo version is totally free and for a unlimited time of use, it have all the features of the professional version but the number of parts is limited. However, it is possible to simulate quite big circuits with it.

A simulator is very useful to design circuit very fast without spending any money for parts, accidentaly destroying them or electrocute yourself ... It is as accurate as the Spice models you use are. Once the circuit work well on the simulator, there is very good chances it work as well in the real life. It is the best development tool ever made.

Everybody who wish learning quickly the electronic should use a simulator, it is the best way to design a circuit without making long and cumbersome calculations because a simulator can calculate millions of times faster than you can do it with a pocket calculator. Calculate a complex circuit that normally need very good skills in algebra and imaginary numbers become very easy to do.

English is not my first language, I am french speaking, so forgive me if my texts sometime a look funny. But there is no better ways than practicing for learn, with the help of a good french/english dictionnary and "Google translate".

The first steps

Here's the link to download this free software :

Free demo, SIMetrix/SIMPLIS analog circuit simulation software

The software can be installed on any hard disk drive, not necessary the C drive ... However, the working directory of SIMetrix is created in your directory "My Documents" but it can be any where else. It work very well with Windows XP.

Here's what look like the command shell :

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The menu of this window is for the general operations of the software, like managing the models and the symbols you can easely create yourself if necessary, like the tubes ...

It is also used to display all what is going on during the simulations and the voltage, currents and power dissipation of the component you have selected using the command "Display Bias Info" in the floating menu which appear with a click on the right button of the mouse :

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The window editor of schematics with which you can place the components among the thousands already included in the SIMetrix libraries or the ones you have intalled yourself. You can load many schematics at the same time using the tabs :

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The "bias Info" of the "command shell" is for the 6CB6 of this schematic after starting running the simulation. Notice the "inline current probe" and the "ground symbol" I will talk about farther.

Here's a curve graphic I made with this circuit using the "DC sweep" on V2 device by changing the V3 voltage for each, from 0 to -5V by 0,5V step, just "like in the real life" :

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This is the graphic window for curves and wave shapes, I will show some of them very often in this blog because it is where the results can be seen.

The curves of any tube, bipolar transistor, JFET or MOSFET can be generated easely this way, and compared to the curves graphics of their datasheets. This is the best way to verify their accuracy.

This was the presentation of the three windows of SIMetrix, there is also a lot of importants "dialog box" for all the functions, types of components and simulations.

About the components

There are thousands of components already included in the SIMetrix libraries, mostly semiconductors, but there is no tubes, leds or light bulb models and symbols. You will have to draw the missing symbols yourself and find the components models you need on the net here and there. The semiconductors factories often give their products models on their site.

I will not talk about semiconductors because there is nothing special to said about them, all what you have to do is placing the types you need on the schematic. But I will talk about all the passive and magnetic components.

Before going any farther, I must tell you what units prefix are used for components values, voltages, currents, powers and frequency from the higgest to the lowest :

T = Tera ( X 1 000 000 000 000 )
G = Giga ( X 1 000 000 000 )
Meg = Mega ( X 1 000 000 )
K = Kilo ( X 1000 )
no unit = X 1 ...
m = milli ( X 0,001 )
u = micro ( X 0,000 001 )
n = nano ( X 0,000 000 001 )
p = pico ( X 0,000 000 000 001 )
f = femto ( X 0,000 000 000 000 001 )
a = atto ( X 0,000 000 000 000 000 001 )

You will never see the extreme ones in any circuit, usually just from pico to Mega are used ...

How to place the components and symbols

There is many ways to place parts on the schematic, the most common ones are in the "place component buttons toolbar" of the schematic window. It is possible to add or remove some using the "configure toolbar" item in the View menu.

To get all the symbols and models, you must select them in the "place menu" :

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Most of the included models are in the lower portion of this menu but the models you install yourself and many more can be found by selecting the "From Model Library" menu item.

The symbols you draw yourself and many other very usefull like fuse and terminal can be found by selecting the "From Symbol Library" menu item.

Beside the voltage and current sources and probes, the most important is the ground symbol ... Every schematic must have at least one ground symbol or no simulation can be possible, it is the reference for all voltages in the circuit, usually call the "node 0" in many simulators.

Also no simulation is possible if there are some "floating nodes" in the schematic but there is some tricks to avoid that, I will talk about them farther.

The resistors

In the "Passives" menu item, there are two kinds of symbols to represent them, the box shaped and the "Z" shaped. Beside their look, the are exactly the same. Usually, I use the "Z" shapped ones for real resistors and the box shapped for the "ficticious" resistors just for simulations purpose.

Here's the resistor dialog box you can access by double-clicking on them :

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This is really self-explanatory, there is something else very usefull to set in a resistor beside is value, it is the rated power dissipation, to do that, you must click on the "Parameters" button :

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Double-click on the "W" and write the dissipation beside, after this is done, you must press the "Enter" key to set it permanently. The dissipation will appear beside the value on the schematic, "10K W=0.25" in this example.

The potentiometer

Also in the "Passives" menu item, the potentiometer is one of the most usefull part in SImetrix, you can set is wiper just like a real one, in is dialog box or with the keyboard "shift up" and "shift down".

When you double-click on a potentiometer :

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You can set the wiper position by writing it from 0 to 1 ( 0 to 100% ) or clicking the up or down arrow for a 5% increment or decrement step.

The "Increment/decrement step size is set for the smallest 0,01% step using the "shift up" or "shift down" key on the keyboard after you select the potentiometer.

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This demo schematic show the 20K volume control with the wiper position at 50%. The arrow of the symbol show where is the 100% side of the wiper position so don't place it upside down ... Notice the 0,25W rated dissipation beside the resistors values.

The default place of the OPamp "type" is not usually there, to move it where you like to, just select the component and click on the "ctrl F7" key, you can do the same with the "reference" using the "ctrl F8" key.

The capacitors

In the "Passives" menu item too, you can find four kinds of capacitors, the normal unpolarized capacitor like the paper, mica, ceramic or film ones, a "infinite capacitor" with no value to set, the "simple electrolytic capacitor" and the "detailed eletrolytic capacitor".

I will start with the "the normal unpolarized capacitor" just call capacitor in the menu, when you double-click on it, this dialog box appear :

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You can set the capacitor value just like for the resistors. Notice there is no "leakage resistance" in this type of capacitor, when you place two capacitor in series in a circuit, the total capacitance is C1 X C2 / ( C1 + C2 ) but this don't work in the simulator because there is no "leakage resistance" and the node between them is "floating".

Click the image to open in full size.

Sometime but rarely, an initial charge voltage have to be set to get the simulation working.

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Click the image to open in full size.

This basic Wien sinewave oscillator circuit don't "start" if the C1 capacitor don't have an initial voltage set, just 1 volt is enough to initiate the first swing ...

There is not much to say about the "infinite capacitor" except it have an infinite value ... But I never think about using it in a circuit yet.

The electrolytic capacitors

To be continued in the next days, weeks and months when I have some spare times ...
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