We had learnt to interface a toy DC motor with the arduino platform. The idea is to design a sensor controlled vehicle which navigates based on the intensity of the light which falls on it.
We used a LDR(Light Dependent Resistor) as a sensor element for the project. The analog value of intensity of the light falling on it is measured and it ranges from 0 – 1024 (10 bit resolution limitation of arduino). We used a dual H bridge IC named L293D to actuate the motor. To get the desired torque, we have selected a geared motor with 300 RPM @ 12VDC.
For this task we used only one geared motor and one half of the dual H Bridge. For initial prototyping we used the breadboard, the enable pin of one half of the IC is connected to 5VDC, two IOs are assigned namely 4 and 7 to control the outputs of the IC. The LDR is connected to the analog pin A0. The LDR circuit is designed as a voltage divider circuit. The analog value obtained from the task is compared continuosly with the threshold limit of 950. If the value is changed the motor will rotate in clockwise direction else in anticlockwise direction.
Solving Rubik’s cube has always been a challenge for me, and I was never interested in solving it. But few weeks ago I got the opportunity to learn the cube. Though initially I didn’t know how to solve it, I was able to learn to solve the cube after spending 4 to 5 hours. I was asked to take Rubik’s cube classes for the 6th graders in Udavi School, so every Thursdays , I spend 40 minutes taking class for them during my lunch break.
The students of Deepanam and Last School were also interested in learning the Rubik’s cube, so a class was taken for them to solve it. During the session I was able to notice that the students were really patient, focused while solving the cube and were also helping each other, this made me feel accomplished and acknowledged.
In Stem Land, we were doing Electrolysis experiment with water in order to explain the children how the electrolysis process works. The Materials that are we used to do this experiments are the following. Salt water, aluminium foil, copper wire, voltage source and two plastic glass. In this experiments water is the best method of producing high purity hydrogen gas. The most important element of the generator is the electrolysis cell where the electrolysis reaction takes place.
The cell consists of two electrodes (an anode and a cathode), which are separated by the ion exchange membrane (salt water). When a continuous 12 voltage is applied to the electrodes on the electrolyser cell, the following reaction happens:
Anode 2H2O – 4e = O2 + 4 H+
Cathode 4H+ + 4e = 2H2
But in-order to produce the highest purity of hydrogen up to up to 99.9995% purity, a platinum catalyst is used at the electrodes.
The students were very focused and eager doing the experiment and were coming up with different concepts.
Abilash who is taking up scaling of STEM Land in Auroville schools wanted to introduce Lego Mindstorms to children from TLC ( Theivan, Meet, and Daniel) who were interested in robotics. I (Sundar) took this opportunity to create a mixed group environment. I knew some children (Murali, Yuvan and Jeeva) who had already built robots using Mindstorms in Udavi and knew how things work. Murail came in early and set up the laptops with the instruction and PDF for building various robots. He initially was very reluctant in working with children with other background. Once all the children arrived in STEM Land we started with a few moments of silence and refreshed the ground rules. Initially they were a bit shy to speak and mingle, but as they started to work it became normal and the goal became important on building the robot. Both of the students were enjoying the session and were working very eagerly to complete (snake bot and humanoid) it within the day, due to lack of time they had to store the work in progress to be continued later next week.
As most of the students were new to electronics, they were asked to build a simple battery holder ( Aravind Gupta Toys) and to measure the voltage from the battery using the multimeter. They were given different batteries and were asked to measure the voltage by keeping them in series. They were able to notice the change in voltages in different batteries and enjoyed the process. The students helped each other by sharing their knowledge to their younger buddies and we were able to see the Peer Learning build up. At the end of the day they were able to learn about voltage, LED, copper, multimeters, and make the LED glow.
While preparing for the electronics class. we took “Automatic street light using LDR” as the circuit, where “LED” turns ON in dark, and turns OFF in bright place.
After giving the circuit connection, the LED didn’t turn OFF when it was bright. So we started analyzing the circuit, then we found out that, the R1 resistor was low when compared to the resistance of the LDR under the brightness.
We calculated the resistor value of R1, by assuming that
Vbe = 0.6v was needed to turn ON the “transistor 1”.
Resistance of LDR = 180 kΩ under minimum light for which LED should be OFF (if we further reduced the light, resistance will increase, then “LED” should turn ON and “transistor 1” should turns OFF).
From the calculation, we got that R1 = 13.17 kΩ, we approximate it to 10 kΩ.
This week the students of Auroville schools did a project on Vacuum lift. The task was to lift the glass jar with the use of balloon and not with the hand. When they first set the balloon on top of the jar, the air pressure outside the jar and the air pressure inside the jar were the same. As they lit a small piece of paper and dropped it inside the jar, heat was created inside it and was pushing its way out of the jar. This hot air pushing out past the balloon caused the balloon to wiggle. However, while hot air was going out, no new air was able to coming in (the balloon works like a one-way valve, letting air out but not in). So now there was less air, less stuff, in the jar. With less stuff taking up space in the jar, the pressure inside the jar was less than it used to be, that is, less than the air pressure outside the jar. Since the pressure outside the jar was greater than the pressure inside the jar, a part of the balloon was sucked into the jar due to vacuum. And now the students were able to lift the jar up by holding the balloon from its top.
Whille preparing for the class in Auroville schools about Siphon, the Isaiambalam students were curious how it works and were asking us how we had done it. So, Naveen and I were explaining the students how the siphon works and the different positions, it should be kept for transferring maximum liquid from one cup to another. The students of Auroville schools also enjoyed doing it, they tried out different ways of transferring the water(with single pipe and later with two pipes). They also tried to transfer 1 liter of water equally into three cups and were successful.
The STEM LAND Classes was started in Auroville Schools (TLC and Deepanam) from this week. In the first half of the class I asked the students to make a Spray with the use of straw and a cup of water. Though the students struggled a bit in the beginning they were coming up with different ways of spilling the water. When I gave some clues, they got the idea and started to build their own spray. The students had a confusion on how it works, and so the explanation was given to them about the higher pressure which pushes the water from the cup to the lower pressure of the straw. In the second half of the class, few cast puzzles and games were introduced to the students where they got excited and started playing.
The STEM Land team usually does 10 minutes of concentration everyday in the morning as a routine. This Wednesday(10/07/19) as a change we all booked and went to the Matrimandir inner chamber. We did the concentration for about 40 minutes. It was a different opportunity for all of us to visit Matrimandir as team, which made us feel really good.
“Though I have gone to Matrimandir many times, going as a team was a different experience, while leaving the chamber I felt good and light.”-Abilash
“I was able to still myself, as I have a connection with the place, it was peaceful for me.” – Naveen
“After the concentration I was able feel the peace and felt more concentrated.” – Prabha karan
“During the concentration, I was able pause my background conversations and move forward.” – Sandhiya
“Initially I felt tired before entering the inner chamber, but after the concentration I felted refreshed and focused.” – Murali