VOLTAGE GENERATORS AND PRELIMINARY SOFTWARE SIMULATIONS

In this lesson we will perform the first computer simulations and in particular we will simulate the functioning of direct current generators.

When we talk about simulation we are referring to software that can simulate the functioning of electrical and electronic devices not only individually but also connected to each other.

Among the various software available on the Internet, we have decided to adopt the Proteus software for these lessons, which on the basis of the analyzes we have carried out, is able to provide excellent answers both on the didactic level and on the quality of the simulations. There are free and paid versions of this software but as you can imagine, in all our lessons we will use the free version. We anticipate that this version has limitations although, as we will see, for the educational purposes of this book, these limitations will not emerge.

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Without going any further, in Figure 15 we provide you with instructions for accessing the installation file.

More specifically, use the following link:

https://www.labcenter.com/downloads/

Through this link you will access the download page of the demonstration version (i.e. the free version of Proteus).

Click on this link and execute the steps required for installing the software. These are typical steps common to the installation of any software and therefore no critical issues are expected in this procedure.

Figure 15: Internet page for downloading the free version of the Proteus software.

If you have followed the installation procedure correctly, you will find the Proteus icon on your desktop as shown in Figure 16.

In our case we note (in Figure 16) that we have installed version 8 and in particular the Demo version (again the free version).

As with all other programs installed on your computer, to start the Proteus software, simply double click on its icon.

Figure 16: Icon of the free version of Proteus software.

With this action you will open the window shown in the following figure.

Figure 17: Main window of the Proteus software.

You will notice that all the various menu options are in English and from a first analysis, it would seem that it is not possible to easily get a version of the software working with other languages. This should not be an element of concern for those who are reading this book, which is written in English! Speaking generally, it can be said that this apparently negative element must be taken as an opportunity to refresh one’s English or to learn some English terms in an area where this language is certainly widely used.

The first item of the menu we have to deal with is “Schematic Capture”, shown in the following figure.

Figure 18: Access to Proteus “Schematic Capture”. In the following figure we show a zoom of the button related to this function.

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Figure 19: Zoom on the “Schematic Capture” button.

The “Schematic Capture” button allows Proteus to capture the schematic of an electronic circuit in order to run simulations with it.

After pressing this button, a worksheet will be opened with an editing window that allows you to draw electronic circuits, as shown in Figure 20.

Figure 20: Opening of the Proteus worksheet after pressing the “Schematic Capture” button.

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In Figure 21, we illustrate a detail of the screen under analysis.

Figure 21: Detail of the “Schematic Capture” screen.

It is not important at this stage of the course to go and analyze and learn all the features available in this worksheet, you will learn them as we need them.

For example, in this phase we are ready for the insertion of our first device and since in the previous chapter we have extensively treated the electromotive force generators with particular reference to direct current, we will insert in our schematic a direct-current voltage generator.

As shown in the following figure, we access the library of available components by clicking on the “Library” menu and then on “Pick Parts”. Alternatively, instead of clicking on “Library” and then on “Pick Parts”, simply press the letter “P” to access this menu item.

Figure 22: Selection of the menu item that allows you to pick a component from the Proteus library.

Once this menu item has been selected, a rich list of categories of available components will show up (Figure 23).

Those who are curious can immediately check the great availability of devices, for example we see the presence of analog integrated circuits (Analog ICs), capacitors, diodes and much more if you scroll the bar on the right.

Figure 23: Example of categories of components available in the Proteus library.

Now let’s focus on our first test and let’s take a very common voltage generator: the battery.

This component is available in the “Miscellaneous” category. The name of this category indicates that inside it there are various components that cannot be classified in a specific category.

Once you have selected this category (Step 1 of Figure 24), you will find (in the central panel) the complete list of devices belonging to this category (Step 2 of Figure 24). In particular, you have to identify the component “Cell – Battery (single-cell)”. Once you have selected this device, you will find on the right the relative circuit symbol which for many of you will certainly be familiar (Step 3 of Figure 24); it is the classic circuit symbol of a battery or in general the circuit symbol of a DC voltage generator (where DC stands for Direct Current). The longer line of this symbol indicates the positive pole while the shorter line indicates the negative pole.

Figure 24: Selection of the battery to be inserted in the circuit. The figure below is a zoom of the figure above.

At this point everything is ready for the last step (Step 4 of Figure 25) which simply consists in pressing the “OK” button to confirm the choice.

Figure 25: Confirmation of the choice by clicking the “OK” button.

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At this point Proteus will switch to the worksheet on which the battery symbol can be placed anywhere by clicking once with the left mouse button. You can move the symbol in the desired position and once satisfied, you must click on this position a second time with the left mouse button (Figure 26). With this last operation you will have successfully completed the placement of your first circuit component.

Figure 26: Steps for the placement of the battery in the worksheet.

We note in Figure 26 two important details: Proteus has automatically chosen a symbolic name, or better to say a label, for our device; specifically it associated the label “BAT1”. This is an automatic choice performed by the software, but if this does not satisfy us, it will be possible to modify it as we will see in the following.

Another automatic choice made by Proteus concerns the voltage of the battery, equal to 1.5 V. This choice derives from the fact that a single cell that makes up the common batteries is able to generate about 1.5 V. To give a practical example, we can note that the 9 V batteries that we all commonly use in our electronic devices are made up of six 1.5 V cells and therefore 6 x 1.5V = 9V.

The attentive readers will have noticed that in choosing our device to be inserted in the circuit, we chose the “CELL” component, but immediately above in the list it was available the “BATTERY” component which is described as a multi-cell component (Figure 27) thus indicating the possibility of being able to obtain different voltages thanks to the connection of several cells together.

Figure 27: Note the possibility to select the “BATTERY” device instead of the “CELL” device.

In our case, we preferred to choose the “CELL” component for a simple reason: the multi-cell battery symbol is a bit bulky (see Figure 28) and less common in electronic schematics and therefore less suitable for an introductory lesson.

Figure 28: Circuit symbol of the “BATTERY” device.

On the other hand, returning to our single-cell battery, it will be showed in the following that Proteus still allows you to change its operating voltage and therefore it is not strictly necessary to resort to the multi-cell battery to obtain voltages values different than 1.5 V. However, if we want to be rigorous, every time we want to indicate a battery with a voltage multiple of 1.5 V we should use the multi-cell battery symbol.

For completeness, it must be said that in the books of the sector the single-cell battery symbol is also used as a generic symbol of the DC voltage generator (remember that DC stands for Direct Current). Therefore, in this sense, it can be used to indicate a voltage source of a generic DC voltage.

Well, made these clarifications, let’s try at this point to make some changes to the device just inserted in the circuit. Let’s start by changing the name associated with it. To do this, we move the mouse pointer closer to the label “BAT1” and we will see that it will change its color (Figure 29).

Figure 29: Selection of the label associated with the battery inserted in the circuit.

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Then we have to click twice with the left mouse button on the label in order to open a configuration window where the string field can be changed as desired as shown in Figure 30.

Figure 30: Configuration window for the label associated with the battery inserted in the circuit. The red arrow indicates the string field to be modified.

As shown in Figure 31, in this example we have decided to identify our device with a simple label: “PILA” which is the Italian name for “battery”. We chose the Italian name for this device in honor of its inventor, Alessandro Volta!

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Before clicking the “OK” button, you can also try the options related to the rotation and alignment of the text of this string. In our case we have decided not to modify them and we can therefore press the “OK” button to confirm the changes made in the configuration window.

Figure 31: Insertion of the “PILA” string as a new label to be associated with the battery inserted in the circuit. The red arrow indicates the modified string field.

If you have correctly followed these simple operations, you will now find the label “PILA” associated with the voltage generator inserted in the circuit.

Figure 32: Label associated with the battery inserted in the circuit.

Now let’s try to change the voltage of this generator by clicking this time on the 1.5 V value next to the circuit symbol. A window similar to the previous one will be opened but this time the string field contains the voltage value expressed in Volt to be associated with the battery (Figure 33).

Figure 33: Changing the voltage value associated with the battery inserted in the circuit. For example, we set the voltage of our voltage generator to 4.5 V and then we can press the “OK” button (Figure 34).

Figure 34: Configuration of the voltage value to 4.5 V, which is associated with the battery inserted in the circuit.

As indicated in the following figure, with this operation we have successfully completed the configuration of our first electrical component.

Figure 35: Worksheet appearance after applying the desired configurations to the battery.

So far we have mainly focused on setting the voltage value of the voltage generator. It would also be advisable to check whether this setting was made correctly. In other words, we would like to measure the potential difference across the battery placed in the worksheet.

On the other hand, even in real cases, given a voltage generator, it is often necessary to measure its voltage for several reasons. For example, it may be necessary to measure the voltage of a battery to check if it is discharged, or to measure the voltage of a power supply to check whether it works correctly.

The measurement of a potential difference or voltage, which we remember is expressed in Volts, can be carried out with an instrument called a voltmeter. Generally, a more complete instrument called a tester or multimeter is used, the latter name reflects the fact that this instrument is capable of measuring multiple quantities. The multimeter shown in Figure 36 is a typical example of a digital multimeter that can be purchased for a few tens of euros/dollars.

Figure 36: Example of an cheap digital multimeter.

By consulting our website, https://NPROnline.tech, you can find several tips for purchasing a valid and inexpensive multimeter to carry out your electrical and electronic experiments.

The multimeter is characterized by a typical knob or selector switch that allows us to choose the electrical quantity to be measured (Figure 37).

More specifically, the tester shown in the following figure allows the measurement of:

• The capacitance of capacitors, which is measured in Farad;
• The resistance of resistors or conductors, which is measured in Ohm;
• The gain of transistors, which is dimensionless;
• The frequency, which is measured in Hertz;
• The direct-current voltage, which is measured in Volt;
• The alternating-current voltage, which is measured in Volt;
• The temperature, which is measured in degrees Celsius;
• The alternating current, which is measured in Ampere.
• The direct current, which is measured in Ampere.

Figure 37: Quantities measurable with a typical inexpensive digital multimeter.

We have seen that batteries represent DC voltage generators and therefore in the case of measurements relating to these devices we will have to operate with the direct voltage section of the multimeter.

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We will therefore have to set the multimeter selector switch on the measurement of direct voltages as shown in the following figure.

Figure 38: Configuration of the multimeter for the measurement of direct voltages.

The red arrow shown in Figure 38 points to the direct voltage symbol, consisting of a V (which recalls the Volt unit) with a double line, a continuous line and a dotted line below it. The presence of different selectable values allows us to define the most suitable range for the measurement to be made. If we intend to measure very low voltage values ​​then we will select a very low range in order to obtain a good measurement accuracy, on the contrary in the case of high voltages we will select a high range which avoids reaching the full scale of the instrument.

In other volumes we will intensively use the multimeter in the laboratory while as regards the purposes of this volume, the concepts just explained are sufficient to continue our analyzes with the Proteus software.

Indeed, let’s go back to the Proteus software to illustrate how it is possible to measure voltages using a simulated voltmeter.

As shown in the following figure, in the toolbar on the left of the worksheet we have to look for a button that represents an analog multimeter with the red needle. By clicking on this button you will find all the measuring instruments that Proteus allows us to simulate and use.

Figure 39: Access to measuring instruments available in Proteus.

From the list of available instruments (Figure 40), we select “DC VOLTMETER”, which represents a DC voltmeter where (again) “DC” is the acronym for “Direct Current”.

Figure 40: Selection of the DC voltmeter.

Let’s click twice on this menu item and move the mouse pointer on the worksheet, then we click again where we want to place the voltmeter.

If you have followed these operations correctly, you will find on your worksheet the battery and the voltmeter positioned as shown in the following illustration.

Figure 41: Appearance of the worksheet after inserting the voltmeter.

Obviously you can position the two devices as you prefer, but for the moment we suggest you to follow the layout proposed here.

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Before drawing the connections between the two devices just inserted in the worksheet, let’s go back to the real multimeter for a moment and highlight another important detail: the test probes or leads. These are two rigid conductors with a metallic tip and are connected to the multimeter with two colored cables, one red and the other one black (Figure 42). By means of the test leads it is possible to access the points of the circuit where we want to perform measurements with the multimeter.

Figure 42: Example of multimeter test leads.

The red and black color of the test leads recalls the known convention which establishes that the red color refers to the positive polarity and the black color refers to the negative polarity.

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Even the multimeter, in fact, has its own positive and negative polarity and it is therefore advisable to connect the test leads respecting the color convention just described, as shown in the following figure.

Figure 43: Correct connection of the test leads to the connectors of the multimeter.

We have seen that, even for the simple circuit that we are drawing with Proteus, we must make a connection between the voltmeter and the battery that represents the device to be measured.

Having to measure a voltage, we will connect the positive tip to the positive pole of the battery and the negative tip to the negative pole of the battery.

It is therefore necessary to draw the connections that simulate wires (Figure 44).

To do this, simply move the mouse pointer to one end of the battery and click once with the left mouse button to begin drawing a wire. You will notice that it is also possible to draw 90-degree connections by clicking in the position where a direction change is needed; it is possible to make multiple direction changes without interrupting the drawing operation. In particular, with two 90-degree curves and with a third click you will be able to electrically connect the positive pole of the battery to the positive probe of the voltmeter, as shown in Figure 45.

Figure 44: Drawing of electrical connections with Proteus.

Figure 45: Final click to complete the first connection between the battery and the voltmeter.

If you are not satisfied with a certain wire inserted in the worksheet, simply move the mouse pointer over the connection to be removed, press the right mouse button and select the “Delete Wire” menu item.

Before proceeding, we recommend that you do some practice with drawing and deleting electrical connections in order to familiarize yourself with Proteus tools. On the other hand, these features are typically also adopted in other simulation software and therefore represent basic operations to be learned regardless of the software used.

Figure 46: Procedure for deleting an electrical connection.

Once you become familiar with Proteus drawing tools, you can complete the connections between the voltmeter and the battery. In particular, you should be able to draw a circuit similar to the one shown in the following figure.

Figure 47: Final circuit connecting the voltmeter to the battery.

We are now ready to put into operation the circuit just created. In more precise terms, we must run the simulation of the circuit. To do this, we press the button indicated by the red arrow in Figure 48, which will start the simulation as highlighted in the relevant zoom (black box of Figure 48).

Figure 48: Running the circuit simulation.

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Once the simulation has started (Figure 49), we will notice that the voltmeter display will light up correctly indicating the battery voltage value, i.e. 4.5 V.

Figure 49: Circuit simulation and measurement of battery voltage with the voltmeter.

In the lower part of the worksheet you will notice (Figure 50) that the simulation start button is now colored in green to indicate that the simulation is in progress and at the same time a stopwatch indicates the duration of the simulation.

Figure 50: Appearance of the worksheet during the simulation.

As an exercise you can now try to change the voltage value of the battery and check if the voltmeter is able to measure it correctly.

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However, you will notice that any attempt to modify the circuit leads to the generation of messages highlighted in yellow (Figure 51), which aim to specify that modifications to the circuit are allowed only when the simulation is not in progress.

To stop the simulation, simply press the button with the typical “stop” symbol, shown in Figure 52.

Figure 51: Message issued by Proteus when trying to modify the circuit while the simulation is in progress.

Figure 52: Indication of the button to press in order to stop the simulation.

Once the “stop” button is pressed, an “end of simulation” message will show up at the bottom of the screen (Figure 53) and we can therefore make changes to our circuit.

Figure 53: Appearance of the worksheet after stopping the simulation.

As an example, in Figure 54 we report the simulation of a circuit with a 38.3 V DC voltage generator named “GEN DC”. Obviously, we are free to choose any other name or voltage value.

By running the simulation, you will notice how the voltmeter correctly will indicate the generator operating voltage.

Before continuing, we suggest carrying out several tests in order to familiarize yourself with these first devices and tools of the Proteus software.

Figure 54: Further simulation test with a 38.3 V voltage generator.

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