Around 37 gevernment school teachers and people 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. People saw what the children were upto in Isaiambalam school. We had a saturday school and all the children were working on the EBDs.
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.
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.
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.
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.
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.
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.
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
Task 1: Test different layouts with IRSIM
Task 2: Whoever didn’t complete XOR should complete XOR and test it out using IRSIM
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.
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.
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.
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.
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.
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.
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.
Children of Isaimbalam were very much interested in Soldering and making simple circuits. We got many Vega kits were the circuits are already printed in a PCB. Children study the datasheet of a particular circuit and solder. Children from 6th and 7th soldered few kits. They were very happy when some of them worked.
Since they are young and new they made mistakes by flipping few components here and then but they tinkered with my help.
Circuits like Disco light, Light sensor and water level indicator worked.
Bala was so happy when we were testing the water level indicator and the light one by one lighted up. Auyush also connected a buzzer to indicate low light.
Ayush and Swetha testing low light sensor
Ayush and Swetha testing low light sensor along with me
Children wanted to make a recycling water system to water the magic garden. We thought of using the waste water from the kitchen to water the plant since so much of water is daily used to wash the vessels, clean vegetables etc. To know the amount of water used daily for the kitchen we need to know the volume of the tank. Kavitha told that the volume of the kitchen tank was 2000 L.
To make sure of what we know already we measured the height and circumference of the cylindrical tank in order find the volume of the tank.
To measure the height of the tank we used a bamboo stick.
Children marked the height of the tank on the bamboo stick.
Measure Circumference to determine radius:
We used thread to know the circumference.
Children took the thread around the circular shaped ring and marked on the thread.
The challenging part was we was not able to find the measuring tape. Then we came up with an idea to use the metre scale chiildren already used.
We found that the height of the tank was approx 3 m and Circumference to be around 3.14 m.
Through this we found out that the radius was half a meter.
Finally we found out that the tank volume was approximately 2355 L.
This might be an error with calculating the circumference of the circle because we found the distance outside the ring and not inside.
Measuring the circumference of the circle with the one meter scale and the left over part was measured using a 30 cm scale
From Left: Ajay, Gurumoorthy, Pravin, Kalai
Children measuring the length of the bamboo stick to measure the height of the tank. They used the same thread to measure the length. They marked 3 m on the thread in order to do this