The Simplest Line Follower – Upgraded! [Updated]

Hello everybody!

Apologies for not writing for so long! Work has kept me really busy so I wasn’t able to do much till now.

Last week I finally got time to do a bit of work. I made my own PCB :). I wish I had learned this back in college. It have would saved me so much time.  What PCBs did I make? The line follower circuit (Click me to open tutorial) I explained before. That design had two very irritating problems. Firstly the wires would keep breaking off and I would have to re-solder many times. Secondly, the cardboard mounts would keep bending.

The new robot uses very little wiring. None of the wires have been soldered. I have also replaced the mounts for the sensors. I will describe everything in today’s post. Read more of this post

Breaking it down – The .SUBCKT

Having done so many simulation examples, ever wondered how complex actual circuits can be? When you go on to design a circuit with some application it won’t be just one amplifier or one rectifier. It’ll have dozens of blocks. How do you fit all that in one schematic? Well you can’t – at least not without getting totally mixed up with where each block is. Thats where hierarchical design comes in. This means that you break down a system into blocks. Break these blocks down even further till you get the simplest ones – like a tree branching out and having leaves at the end. The advantage of this is that most of the time, these “leaves” will repeat across your circuit and with a hierarchical design, these circuits need to be defined just once and reused again.

I hope you have read my previous tutorial on symbol creation in gschem as well as other tutorials on SPICE. You can get these tutorials by pointing your mouse to the Tutorials menu at the top and then selecting SPICE. You need the symbol of the previous tutorial to go through this one. Click Here to go to the symbols creation tutorial.

We will first look at a few op-amp circuits. I will be using LM741 for the examples. You can get the model (and many others) from Texas Instruments. Next we’ll build a two-stage BJT amplifier using a single BJT amplifier as a building block. Just like last time, I will explain only what is new. So lets begin, with my favorite part of analog circuits – operational amplifiers :)

Read more of this post

Simulating Circuits – More Examples!

Hope you liked my previous tutorials on SPICE simulation in Fedora Electronic Lab. Well this post comes a little late because I had a lot of circuits in mind. So take a deep breadth and get ready for Part 3! :)

I’m assuming that you’ve read through the previous two tutorials and that you are now comfortable with using gschem. After this tutorial, you must go through the ngspice manual atleast once. I’ll be moving a bit fast from now on because there is a lot to cover. If something is not clear, feel free to post a comment. I also assume that you’ve completed a course on analog electronic circuits. If you are currently in such a course, go through the circuits you are familiar with and come back later.

Remember to plan a directory structure before each example. Also, the models for the transistors are available from Fairchild Semiconductors and diodes from Diodes.com. I’m not posting these here due to copyright restrictions.

A quick recap:

  1. You draw you circuits in gschem.
  2. Generate the netlist by running: gnetlist -g spice-sdb -o <output_netlist.net>  <input_schematic.sch>
  3. Always check the netlist once yourself. Also see which are the input and output nodes.
  4. Simulate the circuit using: ngspice -b -r <raw_file.raw> -o <log_file.log> <netlist.net>
  5. Finally open the waveform viewer by running gwave <raw_file.raw> and dragging the output you want to see to the panel.

Ready? Go! Read more of this post

Circuit Simulation in GNU/Linux – Lets begin!

Welcome back! :)

As promised, here is the first of my tutorials on EDA in GNU/Linux. In this post we will start with SPICE simulations. Please remember that I’m a total beginner to these tools as well so I could be wrong at places (post a comment and I’d be happy to correct) and that my examples will remain very simple.

Prerequisites

For this tutorial you’ll need these tools installed.

  • gEDA gschem – A schematic capture program.
  • gnetlist – a program that converts your schematic to a netlist.
  • ngspice and gnucap – circuit simulators.
  • gspiceUI – A graphical circuit simulator.
  • gwave – a waveform viewer.

This tutorial assumes that you have taken up a course on basic electronic circuits. It would help if you know how to write a spice netlist but its not a necessity. Read more of this post

EDA in GNU/Linux

As I mentioned in my previous post, I will be posting a few tutorials on EDA in GNU/Linux. EDA, Electronic Design Automation, is basically a class of tools which make an electronics engineer’s life a lot easier. (Wikipedia article). These tools are used by every company or institute. Most of you would have heard of SPICE (known popularly as PSpice), a circuit simulation tool. Many similar tools exist for analog and digital circuits, VLSI design, embedded systems and PCB (printed circuit board) design. However, most of the well known proprietary tools are very costly for an individual to buy and use. In college, students end up using cracked (which is illegal and I discourage this) versions of software. Evaluation versions do not have most of the important features or are valid for just a few days. Read more of this post

Dual Display!

Dad bought me two 20in monitors last week (Thanks dad! :)). I need two monitors to work and I couldn’t manage with a single monitor while working from home. The new monitors are DELL IN2020M – 20in LED HD monitors. Pretty cool eh? I just managed to get both my monitors to work on Fedora. Here is a pic: Read more of this post

Cookie the Table Following Robot – Tutorial

I’m back again for another tutorial on robots. This one will be on the table following robot of which a video was posted earlier. For those who haven’t seen it, here is the video again (Wish I had a larger table :( ):

Like it? Read more of this post

….and back to Bangalore!

Well as the title says, I am back to Bangalore. Returned more than a month back – July 17th to be precise. Didn’t post an update because I didn’t get time. I moved back because I got another (and better) job offer here. I currently work for Cortina Systems and I love the new place :). Keep checking back for continued posts on robots and now on some digital chip design in Verilog.

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