Fruits and vegetables drawing

~Santhosh and Sandhiya

Drawing is a process that all children naturally engage in, from the time they first discover they can hold a crayon.

I have collaborated with English Teacher, she was teaching spelling of fruits and vegetables for 3rd grade.She said she was finding difficulty in children to identify names of fruits and vegetables even though they can spell it after teaching.So we decided to make children to draw, colour so that it helps to retain in their memory.

Children were given names of fruits and vegetables in English class and later practiced them in Drawing class by drawing, coloring and naming them.We noticed that children were more engaged and enjoyed while learning English through Drawing.

Material Required/Tools:-

  • Pencils
  • colors crayons
  • sketches

In the above picture, vegetables were drawn on the board and asked the children to identify the vegetable and write the spelling of it.

In the above picture, Fruits were drawn on the board .

The outcomes of learning this art form in the students:

  • Children learned Fruits and vegetable names
  • They can identify
  • They can draw
  • They can Spell

Various benefits include the following skills:

  • Eye-hand coordination
  • Self-confidence
  • Fine and gross muscle development
  • Observation

In the above picture:-

Step 1 : drawing it

Step 2 : writing the spelling.

Step 3 : Colouring.

Step 4 : sketching the outline.



Using gears for ratios

7th in Udavi children were learning ratios. We used a crank fan and used a spur gear system (in the pictures) to spin the blades around and make a breeze. The faster the fan turns, the stronger the breeze. Using a big gear to turn a small gear makes it easier to turn the blades quickly. For one full turn of the big gear, the small gear spins around many times. How many times it spins depends on the number of teeth both gears have (gear ratio). The spur gears turn the blades much faster than if you turned the blades directly with a crank. Using this crank fan, we showed 1:1 ratio up to 1:5. Showing it visually gave children the confidence to understand the ratio concept.

We gave the students another gear pair as an example for further examination: If the 75-tooth driver gear rotates 3 times, how many times will a 15-tooth driven gear rotate? What if the 75-tooth driver gear rotates 5 times? By focusing on the relationship between the gears. In this case, the 15-tooth gear rotates 5 times for every rotation of the 75-tooth gear. This is true regardless of the number of times the 75-tooth gear rotates. This brought us closer to the gear ratio of a 75-tooth driver gear and a 15-tooth driven gear and what they do in class as the gear ratio is 1:5.

Children understood that.

A colon is often used to show a gear ratio:

gear ratio = rotations of a driver gear: rotations of a driven gear.

Children when seeing it visually it gives confident to build different numbers to find the ratio. The session was interesting for the children. Children sheared their learnings to each other and started working in peers.

Cycle Safety light

For quite a long time (year and a half), kids in the electronics lab have been working on breadboard circuits which they build and then dismantle. They built quite a few circuits this way working with LEDs, Opamps, comparators, 555, microphones, speakers etc. We found that generally one in 20 kids to whom the circuits were introduced become interested to come regularly to the lab in the evenings at the expense of their free time which they usually use to play. A visitor from Austria expressed surprise that any kids at all turned up at the lab at the expense of play time.

Sanjeev and Siva both suggested that this number (1 in 20) would go up if we focussed on some practical circuits which the children could use in their daily lives (and also show their parents, friends and relatives) instead of just making toy circuits on the breadboard which they would proceed to dismantle to build the next circuit. Obviously this is a bit harder and a bit more time consuming for some of us, and that’s why we stayed in the comfort zone (among other reasons) for all this time. Well, staying in comfort is not a universal value and it was clear that changes will have to be made.

So we have now (finally!) started on practical applications. Two of these are

  1. An outdoor light that turns on automatically when the sun sets and turns off automatically when the sun rises (Blog post to come).
  2. An indoor light that turns on when there are people in a room and turns off when people have left the room or staying still (Blog post made by Manogar and Sundaresan)

The third was an idea that came from kids themselves. Their mothers are understandably worried when they use their cycles at night. Cycles owned by the kids have no back lights to warn motorists who approach the cyclist from behind. So it was decided that a light at the back of a cycle that flashed red light once a second was a fine practical circuit. Humans (indeed all predators) are sensitive to movement rather than stillness and to flashing lights rather than still lights. They are also more sensitive to Red and White flashing lights than to any other color.

So an astable multivibrator was built based on the 555 chip which the children first tested on the breadboard and then soldered it on the PCB with help from C3StreamLand youth. An 8th standard student from Udavi school called Ajay took up the challenge to design the structure to house the circuit and to also mount it on his cycle. The student you see with the cycle and the flasher in the attached photos and videos is Ajay.

Ajay’s next target(s)

  1. Make it waterproof
  2. Make it robust to rough riding
  3. Power it off a Dynamo instead of a 9V battery as is being done now

Smart dustbin using Arduino

The smart dustbin is built on a microcontroller-based platform Arduino Uno board which is interfaced with the Servo motor and ultrasonic sensor. An ultrasonic sensor is placed at the top of the dustbin which will measure the stature of the dustbin. The threshold stature is set at a particular level. Arduino will be programmed in such a way that when someone will come in front of the dustbin the servo motor will come into action and open the lid for the person to put the waste material into the dustbin. The lid of the dustbin will automatically open itself upon the detection of a human hand.

Servo Motor:

SERVO MOTOR is an electromechanical device that produces torque and velocity based on supplied current and voltage. It can push or rotate an object with great precision. Servo Motor SG-90 is used. It will perform its angular rotations when a signal will be provided by the microcontroller. The servo motor rotates approximately 180 degrees (90 in each direction).

Infrared sensor:

IR SENSOR is a radiation-sensitive optoelectronic component with spectral sensitivity in the infrared wavelength. It is used for object detection.

Connections: –

The Red Pin of the Servo Motor is connected to Arduino 3.3v. The Black Pin of the Servo Motor is connected to Arduino GND (Ground). The Orange Pin of the Servo Motor with Arduino Pin 8. VCC of the sensor is connected with Arduino 5v.

The Smart Dustbin as you can see in the picture above is built using Cardboard. This is a custom-made Smart Dustbin equipped with HC-SR04  Sensor, Arduino, and a Servo Motor. It is programmed using the Arduino code.


Servo myservo;
int angle = 0;
int angle step= 50;

void setup(){
void loop() {
if(digitalRead(2) == HIGH){

Once there is no one in front of the  Sensor the Smart Dustbin Lid remains closed.

The smart dustbin is a carefully designed solution that solves the social issue of waste disposal.


A session with Last School Children

On the 28th of July, the STEM Land team visited Last School for a session with them. The facilitating team Prabhaharan, Arun, and Illamkathir along with the last school children worked on RTL tools, seven segment displays, Cast puzzles, and the homopolar motor.

The session started with a few minutes of meditation. The team started the session with the Radical transformational leadership tool that helped children identify the universal values they stand for. Then the team helped the children identify their socialized fears and how courage is not the absence of fear, but the ability to act despite fear.

Later, we learned about the Seven segment Display and its primary uses. Our team explained how to use a multimeter and analyze the SSD and showed a demo. With that reference, the children worked on it and completed it.

Later, the working of the homopolar motor was demonstrated to the children. A Homopolar motor is one of the simplest motors built because it uses direct current to power the motor in one direction. The magnet’s magnetic field pushes up towards the battery and the current that flows from the battery travels perpendicular to the magnetic field. Students had a great time making it.

The whole session was engaging, encouraging, and enlightening. It was a great learning for everyone and we thoroughly enjoyed working with them.

Students from Last School requested to come to STEM Land on Saturdays to learn programming like Scratch and Python.  We will start such sessions soon.

Vaughn cube

Vaughn cube is for children who find visualization easier rather than memorizing the multiplication tables.

Elements of Vaughn cube:

  • Numbers.
  • Pictures.
  • Colours.

Construction of Vaughn cube:

  • 4 sides = 4 walls.

Each wall has a specific color.

  • Numbers are arranged as follows:

Odd numbers- Diagonal.

Even numbers- In the middle.

  • Pictures-Specific arrangement based on the sound they make.

For eg: Tuna- T, and n.

              Nose -N and s.

Working with Vaughn cube:

  • Create a room as shown in the image with the numbers marked.
  • Ask children to practice the objects along with their position on which number the object comes.
  • Make it clear for children to see that it is the same object between 3 to 4 and 4 to 3.
  • Let children study the base picture and introduce the different words.
  • It’s important for the children to know the orientation of the room as they will remember objects based on their location rather than the numbers they are in between. This is how the mind castle works.
  • There are different charts for tables 3,4 5, etc.


  • Introduce all the images in the Vaughn cube and ask children what they are along with the sounds.
  • Make children practice the names of the objects and see if they can identify the sounds while saying the names of the objects.

Eg: Tuna-t,n

Deciphering the sounds and numbers:

Map the numbers from 0-9 with the sounds.

  • 1 looks like t.
  • N written sideways as z looks like 2.
  • M written sideways looks like 3 especially small m.
  • Cursive r has a hidden 4 in it.
  • L is logged the bar on top of 5.
  • Ch written with c inside h looks like a 6.
  • Cursive k has a 7 inside it.
  • Cursive f looks like an 8.
  • P reversed looks like a 9.
  • Practice making children map the numbers with the sounds for all the objects.
  • See if children can say the numbers instead of the object name between the two numbers/on top of the number in the room.

Vaughn cube can help children learn multiplication as well as division effectively by visualizing.

Boyle’s Law

Boyle’s law is a gas law that states that the pressure exerted by a gas (of a given mass, kept at a constant temperature) is inversely proportional to the volume occupied by it. In other words, the pressure and volume of a gas are inversely proportional to each other as long as the temperature and the quantity of gas are kept constant. Boyle’s law was put forward by the Anglo-Irish chemist Robert Boyle in the year 1662.

For a gas, the relationship between volume and pressure (at constant mass and temperature) can be expressed as 

P (1/V)

where P is the pressure exerted by the gas and V is the volume occupied by it. This proportionality can be converted into an equation by adding a constant, k.

P = k*(1/V) PV = k

The pressure v/s volume curve for a fixed amount of gas kept at constant temperature is illustrated below.

Experiment using Thinktac kit:

This gas law describes how the pressure of a gas tends to increase as the volume of the container decreases. We use a syringe and balloon to understand the phenomenon.


  • Take a syringe of 60 ml capacity and remove its plunge.
  • Take a small balloon.
  • Blow a small amount of air into the balloon and hold at its neck tightly with your fingers.
  • Insert the balloon through the syringe’s open end and remove it to check whether the balloon can enter freely inside the syringe or not.
  • Now, tie a tight single knot at the balloon’s neck. Ensure that there is no air leakage.
  • Insert the balloon into the syringe to the tip. Insert the plunger back to close the open end.
  • Initially, push and set the plunger at the 30 ml reading on the syringe, with the tip of the syringe open. Now, tightly close the tip of the syringe with your finger.
  • Press the plunger hard as much as possible and observe what happens to the balloon inside.
  • After you reach the optimum level, release the plunger and continue to observe.
  • Now, pull the plunger and set it at the 30 ml reading on the syringe again, with the tip of the syringe closed.
  • Now, pull the plunger to the open end of the syringe and observe what happens to the balloon.


Filling water in the syringe:

  • Take about 100 ml of water in a cut bottle container and the syringe with the balloon.
  • Push the plunger till it reaches the balloon.
  • Dip the tip of the syringe in the water and pull the plunger till the 60 ml reading fills the water.
  • Hold the syringe with the syringe’s tip positioned upward as shown. Shake the syringe and adjust it to push air above the water level.
  • Now, push the plunger slowly for the air above the water level to escape through the tip of the syringe.
  • Push the plunger to remove the excess water into the container, till the plunger reaches the 40 ml reading on the syringe.
  • Now, push and pull the plunger to the closed end of the syringe and observe what happens to the balloon.


Preparing the water balloon:

  • Take another small balloon.
  • Use the same 60 ml syringe and draw about 10 ml of water from the container.
  • Empty the syringe before filling it with 10 ml of water.
  • Now, insert the syringe’s tip into the mouth of the balloon and press the plunger to add water to the balloon’s neck.
  • Pinch the balloon’s neck, at the point where the water is present, to prevent the air bubbles from entering the balloon.
  • Now, twist the balloon’s neck, two times, and tie a knot tightly.
  • Insert the balloon -filled with water into the syringe and close the syringe’s open-end by inserting the plunger.
  • Position the plunger at the 30 ml reading on the syringe.
  • Now, close the syringe’s tip and press the plunger to the maximum possible level. Release the plunger and then pull it to the open end of the syringe.

Observe the difference when the balloon filled with water is within a closed system of the syringe.

We observe in both cases, that when the pressure increases the volume decreases. Similarly, the volume increases when the pressure decreases.


An arithmetic progression or arithmetic sequence is a sequence of numbers such that the difference between the consecutive terms is constant.

For example, the series of natural numbers: 1, 2, 3, 4, 5, 6… is an Arithmetic Progression, which has a common difference between two successive terms equal to 1 (2 -1). Even in the case of odd numbers and even numbers, we can see the common difference between two successive terms will be equal to 2.

This can be observed visually using a graph. If an arithmetic sequence is plotted in a graph lies on a straight line. There is a finite distance between points.

For plotting in a graph, the sequence is written as in the following table.

Sequence of numbers: 3,5,7,9, 11, …


Number of squares(y)


Formula /Pattern




3=2(1-1) +3




5=2(2-1) +3




7=2(3-1) +3




9=2(4-1) +3




11=2(5-1) +3




13=2(6-1) +3




15=2(7-1) +3












tn=a+(n-1) d


The plotted point of an AP is shown below:

Notations in Arithmetic Progression:

In AP, we will come across some main terms, which are denoted as:

  • First-term (a)
  • Common difference (d)
  • nth term. (an)

First Term of AP

The AP can also be written in terms of common differences, as follows;

where “a” is the first term of the progression.

a, a + d, a + 2d, a + 3d, a + 4d, ………., a + (n – 1) d

Common Difference in Arithmetic Progression

Suppose, a1, a2, a3, ……………. is an AP, then the common difference “d” can be obtained as;

d = a2 – a1 = a3 – a2 = ……. = an – an – 1

Where “d” is a common difference. It can be positive, negative, or zero.

The nth term of an AP

The formula for finding the n-th term of an AP is:

an = a + (n − 1) × d


a = First term

d = Common difference

n = number of terms

an = nth term

In the graph, the slope of the line formed by the arithmetic progression is equal to the common difference in Arithmetic progression.

Sum of n terms of an arithmetic progression:

The sum of n terms of an AP can be easily found using a simple formula which says that, if we have an AP whose first term is a and the common difference is d, then the formula of the sum of n terms of the AP is

Sn = n/2 [2a + (n-1) d]

The proof of the sum of n terms can be visualized and derived using the area concept. This can be implemented and observed in GeoGebra.

Suppose we arrange the terms in the AP as shown in the figure we can calculate the area to find the sum of the first n terms in an AP.

This is can be done in two methods:

1.Using the area of the trapezium

2.Using the area of the rectangle.

1. Using the area of the trapezium:

When the terms in the AP are arranged as shown in the figure we can observe that it forms a trapezium. to find the sum of the first n terms in an AP the area of the trapezium can be calculated which gives the result of the sum of the first n terms.

2. Using the area of the rectangle:

Likewise, the terms in the AP can be arranged in such a way that the tilted arrangement and the regular arrangement of the terms form a rectangle as shown in the figure. To find the sum of the first n terms in an AP the total area of the rectangle can be calculated and divided into half to get the required area which gives the result of the sum of the first n terms.

Finding the equation of a line using the arithmetic progression:

Lets take the sequence 3,5,7,9,11…..The nth term is taken as x and its number of squares as y.

As we know tn can be expressed as tn=a+(n-1)d.

i.e., y=tn=a+(n-1)d

We know that a=3,common difference is 2. Substituting we get



y=2x+1 ———- > Equation of the line.

General equation of a line is y=mx+c.

Here we can observe that m= slope =2 = common difference.

c=1 = Intercept (A point at which the given line cuts the y axis).

In an arithmetic progression intercept means the value of sequence, when x=0.

This can be observed in the graph given below.




Rajju Ganit and how we are surprised to learn about ancient mathematics

Rajju ganit (string geometry, cord geometry) aims to teach practical geometry more understandably.

The useful new things students would learn as part of string geometry or Rajju Ganit are

  • Conceptual clarity.
  • Measurement of angles
  • Simplified geometry
  • Measurement of the circle
  • The theory of approximation.
  • Trigonometry.
  • Applications to real life.

There are two main new features:

(1) The cord replaces the entire compass box.

(2) Empirical methods are admitted in geometry contrary to the philosophy of formal math and using instead the philosophy of approximation.

As a part of the learning session through Rajju Ganit, Children used a rope to draw a circle, measure the circumference of the circle, and find the value of Pi.

The circumference of the circle is equal to the length of its boundary. This means that the perimeter of a circle is equal to its circumference. The length of the rope that wraps around the circle’s boundary perfectly will be equal to its circumference. The below-given figure helps you visualize the same. The circumference can be measured by using the given formula:

Circumference of a circle = 2πR =  π D

where ‘r’ is the radius of the circle and π is the mathematical constant whose value is approximated to 3.14 or 22/7. The circumference of a circle can be used to find the area of that circle.

For a circle with radius ‘r’ and circumference ‘C’:

  • π = Circumference/Diameter
  • π = C/2r = C/d
  • C = 2πr

Similarly using the rope, a circle and a square of the same area can be constructed and observed.

Squaring the circle can be done easily using the Rajju ganit method.


Makey Makey is an invention kit by the MIT media lab. With Makey Makey, everyday objects are transformed into touchpads empowering students to interact with computers as creative tools. The computer becomes an extension of their creativity, fostering imaginative play and discovery.

“Makey Makey” is a play on words – students having the ability to Make their Keyboards (“Ma-Key”). The mundane and boring keyboard is replaced by any object that conducts electricity – pie pans, Play-Doh, bananas, and even potted plants – the list goes on.

The heart of Makey Makey is its circuit board that connects to a computer via a USB cable. Building circuits that can be used like a joystick or a keyboard key allows users with no coding experience to use Makey Makey to learn, experiment, and invent.

Makey Makey paves the way for “Integrative STEM Education”. “Integrative STEM education” refers very specifically to instructional approaches that intentionally situate the teaching and learning of science, technology, engineering, and /or mathematics concepts and practices in the context of hands-on engineering, designing, and making.

The Makey Makey kit includes the Makey Makey board, a USB cable, seven alligator clips, six connector wires, and an instruction sheet.

Working of Makey-Makey:

  • Plug in the USB of Makey Makey to the computer.
  • Connect to Earth-Connect one end of an alligator clip to “Earth” on the bottom of the front side of Makey Makey.
  • Hold the metal part of the other end of the alligator clip between your fingers.
  • While you are still grounded, touch the round “Space” pad on the Makey Makey. A green light should appear on the Makey Makey, and the computer will “think” the spacebar was pressed. Also, complete the circuit by connecting another alligator clip to “Space.
  • Experiment by turning various items, objects, or substances into a computer key.

Using Makey Makey with scratch:

Scratch is a programming language where interactive stories, games, and animations can be created. The Chase game is an example of a program made using the Makey Makey. The game is played with the arrow keys and the notes can be remixed for an array of versions.

This chasing game was coded from scratch and used the Makey Makey kit as a joystick controller.

Reflection from Sri Bhavani:
From the Makey Makey hands-on projects with children, they have learned about conducting and non-conducting materials. Current doesn’t flow in an open loop. They learned the open-loop and closed-loop of a circuit. x,y coordinates while moving the sprite.

Piano using Makey Makey.