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Time Narration
00:01 Welcome to the spoken tutorial on Simulating Astable Multivibrator in eSim.
00:07 In this tutorial, we will -

Create and simulate an Astable Multivibrator.

Understand dot cir and dot cir dot out files and

Observe and understand the Ngspice terminal.

00:24 To record this tutorial, we will use-

Ubuntu Linux OS 16.04 and

eSim version 1.1.2

00:36 To practice this tutorial, basic knowledge of electronics is required.
00:41 Earlier, we learnt how to create a schematic for an RC circuit.
00:47 Now I am going to reinforce the idea with an Astable Multivibrator circuit.
00:53 The Astable Multivibrator circuit is as shown.
00:57 Watch me for the next one minute as I create this circuit in eSim.
01:04 A considerable part of this activity has been fast forwarded.
01:49 I am placing a few components and making a few connections.
01:54 It is expected that you know how to create a schematic in eSim.
01:59 In case you do not know, please watch the prerequisite eSim tutorials.
02:50 The partially made circuit schematic is available in the Code files link.
02:55 Pause the video to download and extract the code files on your Desktop.
03:01 We will use the downloaded code file to practice the rest of the tutorial.
03:06 Launch eSim on your machine.
03:09 I have already opened eSim.
03:12 Click on Open Project button on the left toolbar.
03:17 Browse to the Desktop location and click on AstableMultivibrator.
03:23 Then click on the Open button.
03:26 Click on the Open Schematic button on the left toolbar.
03:31 Press the F1 key to zoom into the schematic.
03:35 If you have zoomed in or zoomed out too much, fit the schematic back to default.
03:41 To do this, press the Esc key, and click on the View option on the top toolbar.
03:49 Select the Fit on Screen option.
03:53 It will fit the schematic back to its default resolution. I will zoom in again.
04:03 The wires should be connected end-to-end for components, and not external outlines.
04:11 I will demonstrate a common mistake now.
04:14 Select the Place Wire tool.
04:17 I have clicked on one end of eSim underscore R.
04:22 I will drag it to the exterior outline of the eSim underscore LED and double-click.
04:29 The empty green box shows that the connection is not proper.
04:34 Press Ctrl and Z keys simultaneously to undo the changes just made.
04:40 Let us properly connect the eSim_LED present on the right side of the schematic.
04:46 Click on Place Wire tool on the right toolbar.
04:50 Click on the unconnected node of the resistor. Then drag the cursor till node 1 of eSim underscore LED
05:00 Click once on the eSim underscore LED node to place the wire. Press Esc key.
05:07 Select the Place Wire tool and click on the node 2 of eSim underscore LED.
05:16 Drag the cursor till the wire connecting the adjacent transistor and capacitor.
05:22 Click once on the existing wire. Now press the Esc key.
05:28 If the wires are placed properly, you will see a green dot where the wires intersect.

This is called a junction.

05:37 Right-click on plot underscore v1 and select the Copy component option.
05:44 plot underscore v1 will be tied to the cursor.
05:48 Drag the cursor near the LED on the right side.
05:53 Place it next to the LED by clicking once on the editor.
05:58 Click on Place Global Label on the right toolbar, to place a global label.
06:04 Click once on the editor screen. Type the text LED2 and click on OK.
06:14 LED2 global label will be tied to the cursor.
06:18 Place the LED2 global label near the LED on the right side, by clicking once on the editor once.
06:25 Rotate the global label if required.
06:30 Right-click on eSim_CP1.
06:34 Choose the Edit Component option, and select Value.
06:39 Erase the value eSim underscore CP1 using Backspace key and type 22u. Click on OK.
06:49 Note that we are using polarised capacitor.
06:53 Right-click on eSim underscore R.
06:57 Place the cursor on Edit Component, and select the Value option.
07:04 Erase the value eSim underscore R using Backspace key and type 1k. Click on OK.
07:13 We will assign a value to the DC source later.
07:18 Connect plot_v1 and LED2 global label to the junction as shown.
07:28 Press Ctrl and S keys simultaneously to save the work.
07:33 Click on Annotate Schematic tool on the top toolbar.
07:38 Click on Annotate option, and then on OK.
07:43 Press Ctrl and S keys simultaneously to save the work.
07:48 Click on Perform electrical rules check on the top toolbar. Click on Run.
07:55 We can see three warnings regarding global label, which can be ignored.
08:02 Click on Delete Markers and then click on Close.
08:08 More information on ERC errors is given in the Additional Reading Material of this tutorial.
08:15 Click on Generate Netlist on the top toolbar.
08:20 Click on Spice tab, and check the Default Format option.
08:26 Then click on Generate option, and click on Save.
08:32 Now I will switch back to eSim main window.
08:36 Double-click on AstableMultivibrator.
08:40 Click on Convert Kicad to Ngspice convertor.
08:44 Type the values for transient parameters as shown.
08:49 Click on the Source details tab.
08:52 Type the value of DC source as 9. You should enter only numeric values of voltages.
09:02 Click on Device Modeling tab.
09:05 Click on the Add button under d1:esim underscore led.
09:11 Double-click on Diode folder, select LED.lib file and click on the Open button.
09:20 Similarly add the library files for d2:esim underscore led
09:26 Click on the Add button under q1:esim underscore npn.
09:33 Double-click on Transistor folder, select BC547B.lib and click on the Open button.
09:42 Similarly add the library files for q2:esim_npn
09:50 Now press the Convert button to convert the KiCad netlist to Ngspice netlist.
09:56 A confirmation dialog box appears, click on OK.
10:01 Click on Simulation button on the eSim toolbar to simulate the example.
10:08 Ngspice terminal and plot windows open along with a Python plot window.
10:15 Ngspice terminal shows the values of the voltages at the nodes.
10:21 Ngspice commands can be entered to see plots in this terminal.
10:27 Type the following text in the Ngspice terminal and press the Enter key.
10:34 We can see the voltage at nodes LED1 and LED2 combined in a single plot.
10:43 Any error will be displayed on the Ngspice terminal or the value will be replaced with a question mark.
10:50 I will switch to Python Plot window.
10:53 Click on LED1, LED2 and IN check-boxes in the Python plot window.
11:02 Scroll down and click on the Plot button.
11:06 If analysis time parameters are not set properly, Python Plotting error will be generated.
11:13 For this particular circuit, step time is in milliseconds.
11:18 Right-click on AstableMultivibrator and select the Refresh option.
11:24 The dot cir file shows the netist file of the schematic.
11:29 It contains the information about the node connections and values of components.
11:35 The cir dot out file is passed to ngspice for running simulations.
11:41 It contains information about the device and subcircuit models used in the KiCad to Ngspice conversion tool.
11:49 It also contains the analysis time parameters.
11:53 Let us summarize.
11:55 In this tutorial, we learnt to-

Create and simulate an Astable Multivibrator.

Understand dot cir and dot cir dot out files.

Observe and understand the Ngspice terminal.

12:11 Please post your timed queries in this forum.
12:15 Please post your general queries on eSim in this forum.
12:20 FOSSEE team coordinates the Lab Migration project.
12:24 FOSSEE team coordinates the Circuit Simulation project.
12:29 Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.
12:36 This is Saurabh from IIT Bombay, signing off. Thank you.

Contributors and Content Editors

Pratik kamble