Learning Festival at Indiranagar higher secondary school in Pondicherry

Learning festival was a workshop which happened in Indiranagar HSC. The workshop was happening for 4 days and we went for 2 days. We were invited to do some session regarding basic electronics. We decided to light up children’s name using a 7 segment display. We took 6 voltage sources, batteries, wires, extension chords, strippers, multi meters, 7 segment displays and our STEMland brochures. On the first day we had three sessions. we started the session with few minutes of concentration. We were informed that per session we will have about 30 students and 4 teachers.

  

  

  Day 1

On the first day the first session was handled by Sanjeev and we all supported him. We got 30 students and we split them in a group 3 to 4. He started the session by showing the example name board made by Saranya. Then he introduced the multi meter. In multi meter he showed them continuity mode. He explained how that once they connect two probes from the multi meter they will receive a beep sound. After that he introduced 7 segment display. Then he gave a 7 segment display to each student. Then asked them to draw it on their note. Next he show how to connect a multi meter with a 7 segment display to light up each segment. He asked them to find pin connection for each  segment. When students figured the pin connection connection he introduced bread board connection to the children. He explained bread board connections and how it works. Then each one of us started to support them in small group. Since we were running out of time. At end of the session children and teacher were able to light up at least 2 alphabets using the display.  Children and teacher felt that they learnt something new and they were excited when they lit the first alphabet with the display. Then the next two session was handled by Sundar. After the session we went around to see other events that were happening in the workshop.

  Day 2

On the second day we had 5 session and each session was handled by a facilitator from STEM land. The first session was handled by Saranya, Ranjith, logeshwari, Poovizhi and Pratap. We also two children from Isai Ambalam School to support us. These two children actually did a great job in handling a group and engaging all the children in their group.

       

A Student who came for the first session couldn’t accomplish what he wanted accomplish. His name was John and he asked that he wanted to come tomorrow to finish his name.We told him to come. Then the next day he turned up and started to connect the 7 segment display to light up his name. He was able to lit his name before lunch time. Then he started to handle a group in the afternoon. The boy was able to inspire a teacher who came to visit our session. Then the teacher also started to learn and he was able to light up 3 alphabets. In the evening the education minister came to meets us that time John showed his work to him and it was an inspiring moment.

    

Inverter with Arduino

Barani from 8th standard wanted to learnt something in electronics. He came and asked that he wanted to build an inverter using a Arduino. It was new for me so I told him lets learn together. Then we took all the components that are need to build a inverter. We started by writing a code to blink a LED at 50Hz. Then we dumped the program in the Arduino. Then we connected it with a CRO to see the square waveform. The square waveform was generated and we were able to see it. Then we connected the remaining circuit on bread board. We used a voltage source from which we got 9 volt DC input and fed it to a transformer. The transformer was giving 230 volt AC output. Then we connected a 5 Watts bulb to the output. The bulb turned on. We leant That using a 9 volt DC supply can give a 230 volt AC output. We really enjoyed doing that. During the week we had a Skype call with a school in Italy. Barani was able to explain the whole process to them. He felt very happy to show and share his project and learnings to them.

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.

Salvaging wires and hacking a 240V to 9V transformer from an adapter

The 7th graders from Udavi School took a project on creating a PA system. To start of we required a lot of wires so the quest for salvaging wires began. The students picked every wire possible in STEMLAND that was not being used, we had a long Ethernet cable that was damaged and removed the outer casing and rolled up the inner wires. Once the required amount of wires were acquired we needed a power supply, a broken adapter that was found among the damaged equipment’s came into good use. We opened the case and took the transformer.

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Then the primary and secondary winding s were checked for connectivity using a multi-meter.

Next the transformer was hooked up to a plug and carefully soldered and covered using heat shrink cables for maximum protection from the input voltage, thus it was ready to be tested.

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The output of the transformer was connected to the oscilloscope, but only showed 2V to 3V. But when tested with a multi meter it showed 8.5V the expected voltage. This was a little confusing. In the end  by accident after removing the power we touched the transformer it was really hot. the adapter that the transformer was salvaged must have had burnt the core of the transformer, a while back. Then the hunt for a new transformer began.

Hardware clock

Recently the STEMLAND name board made using SSD had got dim and the 7th std students took it as a project to fix it. They de-soldered the dim SSD’s and Replaced it with new ones.

Barani got interested in the SSD’s and started powering them up using the Arduino, he manged to code the Arduino to print all the numbers 0-9 using two SSD’s

Then to take a step further he started his quest to build a clock. He had added a counter to light the corresponding diodes  in the SSD along with Sanjeev, this was done using a 9V battery.

As I already mentioned in my blog that Deepanam children built an oscillator. Bharani used the output of the oscillator as an input and made the clock count from 0 to 9.

Bharani making the clock count by removing and inserting the input each time.

Giving input from the oscillator built by Pravina (Deepanam kid).

Arun and Sundar

 

Pre Amp

In Stem land I was trying to repair a preamp which was not working. I opened it and I tried to find the problem. The problem was that the circuit wasn’t connected properly. I made the connection. The preamp needs an Ac input 9 V and 1A  transformer. We bought the transformer and made a cover for the transformer in the Stem land with the 3D printer. The green box was made by 3D printer. Now the preamp works.

Prathap

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Fixing STEMLAND name board, and understanding SSD

Some of the 7th std children took fixing the STEMLAND name board as a project, they started off by learning how a SSD (Seven Segment Display) works. Then they assembled the units in a bread board, but there was a bug they couldn’t power up with a 9V battery or else the SSD would burn out. To tackle this they added resistors to control the current. The other bug was some of the SSD were common anode and other common Cathode:SSDOnce the type was figured out the SSD were powered up and tested.

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Controlling a single LED using two switches

During the electronic class that is held on every Wednesday afternoon at STEMLAND, Muthu had built a circuit and figured out how to control a LED using two switch model.

His working prototype is as follows:

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Video of his prototype:

Two Transistor Oscillator

We built a two transistor oscillator which turns transistors ON and OFF all the time. The speed in which it happens depends upon the value of the capacitor. The higher it is the slower is the process of turning ON and OFF.

Transistor Q2 turns on first as there is now a pathway to ground for C1, C1 begins to charge with its right plate being positive and its left plate being negative through R1.

C1’s right plate reaches a threshold where Q1 is turned on. Turning on Q1 gives a pathway to ground to C2, causing C2 to charge through R2 with a positive voltage on its left plate and a negative voltage on its left.
sch_osc

Simulation of the two transistor oscillator in LT spice.

Output:

op_osc

The green wave represents output of Q2 TRANSISTOR at node1 with reference to ground. The red wave represents output of Q1 TRANSISTOR at node2 with reference to ground.