Author Archives: Arun Surya

Earth Day (comes later)

We found some trash on the way to Isai Ambalam school. We (STEM land team) decided to clean the place. As there was some excitement in what we were up to the children also joined us in cleaning.

Pictures tell rest of the story.

 

What it looked like after we picked up the trash

We made a factory line up where we cleaned and dried the plastic and were able to dry it and stack and segregate it.

When we were drying it out the children imagined that this is what a city from the sky could look like.

Setting up Cadence and Centos

Install Centos:

Did not work:

  1. Installed Centos 32 bit OS.
  2. We realized that Cadence need CentOS 64 bit OS .

To find the OS and CPU do

  • # lscpu
  • It should give something like this:
    • Architecture:          i686 == this indicates the OS
    • CPU op-mode(s):        32-bit, 64-bit == this indicates the OS

Worked:

  1. Installed Centos 64 bit OS KDE version. Download LiveCD version with KDE or other desktop (we did KDE)
  2. Somehow we changed KDE to Gnome version of CentOS.
# yum -y groups install “GNOME Desktop”

Note: If you want  to install a KDE version please use the following command:

# yum -y groups install “KDE Plasma Workspaces”

Below link will help you to install various Desktops:

https://unix.stackexchange.com/questions/181503/how-to-install-desktop-environments-on-centos-7

  1. We installed CentOS 7.4

To check what version of Centos you have use the following command:

cat /etc/centos-release

 

Install Cadence:

Installsacape:

https://www.cadence.com/content/cadence-www/global/en_US/home/support/software-downloads.html

  1. We used Iscape to install all the packages needed for Cadence.
    1. Unzip and untar the file in a directory
    2. tar -zxvf IScape04.23-s012lnx86.t.Z
    3. iscape/bin/iscape.sh

This will open up a GUI:

Iscape is a user interface where we can install packages by giving a control file. This control file will have all the packages and will automatically download , install and configure the packages you want.

This is little tricky. When you load in the control file

  1. Search and give control file

In our case the control file was called

Control_30192_309C233F31F1_3_21_2018.txt

Note:

In installing we got many errors and we were not able to install the complete package.

Install the latest of everything i.e. HotFix if available

  1. The directory of downloads and installs is

/home/stemlandaad/cadence

We missed the name of the user so we created another userWe added something to be able to use the UI to add a user.

# sudo yum -y install system-config-users

 

Configure:

We need to configure the licenses.

http://ece451web.groups.et.byu.net/cadence-help/getstarted.html

After configuring,

To run Cadence:

Start terminal and type

# csh

# virtuoso

Azim Premji and teachers from Government school

Around 37 government school teachers and a team from Azim Premji unversity visited STEM land. We presented a paper on “STEM land in Isaiambalam school” at Sindhanai Sangamam symposium. Some of them were inspired from our talk and they came to visit STEM land. The teachers saw what the children were working on in Isai Ambalam school. We had a Saturday school and all the children were working on the EBDs. The teachers interacted with us as well as with the children. One of the teachers reflected that we were thinking of each child and addressing his or her need differently and that was something she wanted to do in her classroom.

After that they visited STEM land in Udavi school. Children showed them few projects. The teachers also tried to solve caste puzzles. We also conducted a Stewardship session for the them lead by Sanjeev.

At Isai Ambalam School

   

VLSI course

We are conducting a basic VLSI course. Around 16 participants from in and around Auroville are coming in to learn. We are only focusing on Digital layout and understanding basic concepts.

Course outline:

Day 1:

Give an introduction to CMOS technology and fabrication process. Give an intro to CMOS Transistors and it’s working. Introduce people to stick diagrams.

  • Introduction to VLSI technology.
  • Introduction on CMOS transistors and working.
  • Demo on LT spice simulation tool.
  • Introduced CMOS Inverter and ask participants to simulate an inverter in LT spice.
  • Showed a video on fabrication process and manufacturing a chip.
  • Introduced stick diagram and how it helps to get started with layout. Participants drew a stick diagram for an Inverter.

Day 2:

    • Introduced magic layout tool.
    • Helped them to login to our central server through VNC. This helped them to avoid installing magic in their laptops. We haven’t figured out a way to install in windows so far, but Magic sort of works fine in Ubuntu platform.
    • Showed top view and cross section of a CMOS transistor. This helped them to understand the fact that layout is all about top view of the devices.
    • Participants laid out an invereter using magic.
    • Once that was completed we showed them to extract and create a netlist. Netlist helps us to understand the connection and cross check whether the layout we laid out is correct or not.

Day 3:

  • Introduced NAND gate
  • Laying out NAND gate. (Note: We gave a circuit diagram for a NAND gate)
  • Extracting NET list and with the same netlsit draw the schematic usind the netlist.
  • Whoever completes should layout a NOR gate and repeat STEP 2 and 3.

Day 4:

    • Introduced to gates. (OR, AND, INVERETER, NAND, NOR and EXOR)
    • Understand the truth table for all gates.
    • Introduced few rules like Involution law, Idempotency law and De Morgan’s law
    • Task 1: Using NAND gate create OR, AND, INVERETER and EXOR. Draw schematic and derive the logic for the same.
    • Task 2: Build those gates using DM74S00N and bread board and test whether their logic were appropriate.

 

Day 5:

  • Intorduced Hierarchy. Showed how to import models that can be used to create complex layouts.
  • Task: Layout an XOR gate importing the NAND gate built in the previous classes

Day 6:

    • Introduced IRSIM
    • Task 1: Test different layouts with IRSIM
    • Task 2: Whoever didn’t complete XOR should complete XOR and test it out using IRSIM

Day 7:

We wanted people to see a real layout and at the end of the course, layout a micro processor.

  • Showed them a layout of a real chip.
  • There are three main blocks necessary for a micro processor. ALU unit, Memory and Counter. We used full adder for ALU and Flip flops for every bit for a memory and counter.
  • Task: Layout a micro processor

Sat school with Isaiambalam

We had Saturday school with Isaiambalam children in Udavi school. Children were back from republic day holiday. Children had a lot of enthu playing games. Some of the children went to STEMland. Initially they were all playing games. Some of them were  interested in doing something with the computer.

Some of the younger children from 3rd grade were doing programming in scratch. One of the children from 5th grade made an Alice program. He was very excited when he made his first animation in Alice.

One of the children from 3rd grade made a scratch program which made a cat to move when he puts the mouse over the cat. These were tiny programs they made but they were very excited when they could do such things on their own with the computer.

Note: I will share the Alice program and scratch program editing this blog soon.

Sanketh’s visit

Sankith from Asha (One of our funder) visited STEM land. He visited both centres Isaiambalam and Udavi. Children were very excited to show what they have learnt in STEM land. They also showed their projects.

Children showing bamboo torch

4th graders showing the honey bee model

Punithavl showing his MIT app

Mindstorms..

Mindstorms

Sanketh’s Reflections on visiting STEM Land

1245_Site_visit_2017

Making Homopolar motor with 7th graders

Janani and Vishal made a homopolar motor. Janani got excited when she saw this experiment online and she wanted to build one on her own.

Making:

Materials needed: 1*AA battery, 3*neodymium magnet, Coper wire of length30cm.

Step 1: Place the three magnets at the negative terminal of the battery.

Step 2: Bend the coper wire as shown in the figure. Make sure it is not insulated, if so please scratch the wire till you get rid of the enamel.

Step3: Put all of them together. Place the coper bend wire on top of the positive terminal of the battery and other end touching the negative terminal of the battery.

Take a look at the video:

  • The current in this homopolar motor flows in the presence of a magnetic field. When a current flows in a magnetic field, it will experience something known as the Lorentz force. The Lorentz force is what causes the wire to spin around the battery.[1]
  • The wire connects to the battery at three points. One point of the wire is on the positive terminal, and the two ends of the wire are near the magnet, on the negative terminal. The current flows out of the positive terminal and down both sides of the wire. The magnetic field pushes the current outwards, causing the wires to rotate.[2]

sources:

 

 

Half wave and Full wave rectifier

I made a model of Half wave and Full wave rectifier using LT spice.

Half wave rectifier:

A half wave rectifier is a device which makes use of properties of a pn junction diode. A PN junction diode only allows the current when it is forward biased. When it comes to real life application we need DC voltage. This circuit converts AC to DC voltage.

Full wave rectifier:

A full wave rectifier uses two PN junction diode which is more efficient and burns less power. It uses both the cycles of the AC wave and gives a smooth curve.

Spinner: MIT app inventor

A child from 7th grade made a spinner using MIT app inventor. He took 3 weeks to complete the project.

MIT app Inventor: It is an application where you can make mobile app. It is similar to scratch where you can stick blocks.

The child shares his experience in the video and how he made it.