Recent Popular Posts

February 26, 2014

Electronic Math classes

As the Electronics lab has become established I have started to take in kids from 6th and 7th grade for an Electronics class in one Math class a week. The kids have been pushing me to include some electronics in their 'curriculum' and when I found one of them in 7th grade trying to make a lemon battery in my class I could not let go of the opportunity. I usually take half the class and let the others continue with the worksheets with the Math teacher.

For the lemon battery they had a small piece of zinc that had been broken out off an old battery casing. They had wound it to a copper wire.

We talked about a new quantity voltage that gives in the water analogy the height of the water it is raised to and measured what we got from the lemon it was around 0.7 V. One kid was consistently able to find out which end is at a higher potential by putting the leads in their mouth. He said that the side he got the shock from was positive. I didn't try it out, but it was accurate every time I asked him.

We sawed through a battery carefully into two disposing off the material inside into a box and then flattening out the zinc plates. We then cut them into strips that we can use.

We talked about an LED and how unlike a light bulb it works only one way. Most kids have salvaged some LEDs from somewhere and are somewhat familiar with them. We started talking about ways (including the use of the multimeter) of figuring out which way it should be connected. We found four. The length of the leads (if available), the cut on the LED, the shape inside the LED and using a multimeter in the continuity setting. I then told them that they needed more than two 2V to light up an LED.

We used both his lemons and were still around 1.3 V still short of lighting the LED, as we had no other lemons I used a 1.5 V C battery in series. It got us to 2.8 V and enough to light the LED and light it did. Then we tried to squeeze out the lemon juice in bottle lids and were able to get enough voltage in four lids to light the LED.

I built on the experience with a few Xth grade kids as they created sets of wires with copper wire soldered on one side and a zinc plate on the other. I used this with the 6th graders. With 4 lemons and 6 kids it was fun exercise. They connected up two and when they hooked up the third the voltage went down. Then they started talking about negative numbers and remembered that the polarity is actually important and its otherwise like adding a negative number. I couldn't have come up with a better example of a negative decimal number than the one they created. I considered making a game of it, but the kids looked too serious to disturb so I let them at it till they got enough voltage to light the LED and look quite satisfied with themselves.

The other aspect that was easy to address was conversions from milli of a quantity to a whole e.g. mV -> V. This happens quite naturally as they try to interpret the results given from the multimeter based on the range they put it in.

I've also had a few lec-dems using an oscilloscope to explain the differences between AC and DC.

February 25, 2014

Don't panic

A funny incident happened a few weeks back.
One of the students had come to the lab over a holiday to learn soldering. He had been soldering a bus of wires LED 7-segment to a connector and it had looked like the wires would short to each other. He spent an hour being systematic, cleaning the solder tip, using the flux, solder reasonably and redid the bus connections neatly and plugged it into the Arduino.
We were using the OLPC (One Laptop Per Child) laptop to program the Arduino and when he uploaded the code into the Arduino, it blinked a zero and the whole board died (shut down). He looked aghast.
We disconnected the board and I worked with him to solder a 9 V battery clip to a connector so we can power the Arduino off this. When all was done we plugged in the battery and the Arduino woke up counting the numbers as expected.
What had happened was the OLPC USB was unable to supply the current required by both the Arduino and seven segment display and had a overload protection that turned it off.
He asked me how I was calm. I told him I just told myself 'don't panic'. He said he that he was glad that I didn't tell him the same as he every time he has been told that was a time to panic!

February 24, 2014

Organized chaos...

As the electronics lab has been getting better equipped and I have also started working with children at different grades and from different schools at the lab. This has given me a chance to spend more time at the lab, work on different projects and also get more confident on handling larger groups. Here is a look at how the Xth grade electronics classes morphed over time:

1) One area: I had started classes by asking everyone to work on one thing on a bread board e.g. getting a seven segment display to work with a counter, using the 555 timer to generate a clock. The classes were somewhat structured with at least 1/3 of the time being white board based. This helped in getting the ground rules of how to read the pin configurations of ICs, LED displays and how to go about connecting them together. It gave a clear focus to the class and helped me give instructions that could be helpful to many students at the same time. It was easy to manage their questions as they were limited. 
I also used to throw in, one new thing a class, e.g. thermocouple, demo of AC-DC, that kept the interest of doing something new each class.
However, with just one thing to work on it was difficult to keep the interest of the entire class and about 1/3 of the class were not always present: either there was an enthu cutlet in their group that did all the work, or it was not engaging enough for a student in a class and the lights were on but nobody was home.

2) Chaos Rules: To break the monotony of highly structured classes I had attempted letting people take anything in the lab and open it up. For about two or three classes the students opened, pried, de-soldered on old TV screen and whatever other equipment I had accumulated over the yrs. The TV bore the brunt of their salvaging and they extracted the enamel wire from its various components with much glee :). There was a marked difference in the confidence of children to build something, knowing that if something went wrong, they could always take it apart. 
Although, this gave them a sort of undo button, beyond that not much happened. They didn't necessarily want to know more than the name of something the pulled out (as they were not using it). Is this something good to remove? 
Yes, its a high voltage capacitor, it can take up to 200 V.
Great, whatever, lets desolder it.
After a couple of these classes I sat the group down and asked them to list what they had learnt. They said they enjoyed it and learnt how to take something apart, but it stopped there.

3) Two projects: As we started working on the Arduino I transitioned to two section classrooms. In hardware I asked them to solder what they had built before a seven segment display to a counter and wire it up so that it had a common interface. I had asked the software group to wire up the display with resistors to the Arduino so they could count inside and display the digits.
One of my goals was to demonstrate the difference between hardware and software. With the hardware I wanted to string a bunch of counters and show that you can, in principle, extend it beyond what Arduino is capable of (limited by number of outputs). For the software group, I had planned to count backwards as well and demonstrate flexibility that software provides when used along with hardware.
They learnt to solder with a clear goal. The software group that was wiring just the LED with resistors with the Arduino were able to get their projects to work in a couple of classes. The tricky part for them was to take the wires and order them as a bus and solder them to a connector. Soldering wires to a 1 space apart connector is a real test of soldering and their work got neater over time.
The hardware group that had to do the wiring realized that it was much more difficult than breadboarding. As they were learning soldering only one of them was able to complete the board completely and they used the solder for too long and the counter chip burned out.
I was able to order some general purpose PCBs with horizontal tracks which would make the connections much more easy and one group that had really put their heart into this has taken up and are doing it again with the new boards.

4) Organized Chaos:
After some introspection, I felt that the kids still wait for me to walk them through every step of the way and my time becomes the limiting factor on how much gets done. I felt they had learnt enough to warrant more independent work. 
Over the last three classes I broke the class into groups that were clear about what they wanted to do and started chipping at the rest of the students who had not been as involved.
I have fundamentally changed my attitude to allow myself to be less useful and let the students explore more (ok struggle) on their own while giving a general direction or goal. 

Here is an example of what they did in the last class:
1) There are a few kids who have taken what they do more seriously and are working with the Arduino to build an instrument to detect the speed of falling objects. 
2) Another is building the electronics for a model of a traffic light (R, Y, G) coupled with a timer that counts down the time with 2 or three digits (again with the Arduino).
3) There is a game to take a loop across an electronics maze and one group is working on a buzzer that will trip and keep ringing once a wire touches the maze (till it is disabled).
4) One group is working on soldering a counter in hardware with counters. They were the closest to finishing the soldering assignment but their chip burnt out due to excess heat. They are now learning how to use sockets and put the  chip in once they finish soldering.
5) Two groups were working on two solar torches that I have from friends that I fixed, but the batteries had gone into deep discharge that the solar panels could not recharge. They tried to understand the panels, measured the voltages and tried to replace the panels with power sources that would charge the battery. Hopefully, once they charge the batteries we can re-engage the panels and things would work.
6) One student is working on trying to get an inverter to work. He fixed the fuse, tried to fix an LED that was bust, but it bust again. This week he learnt about relays (from group 3) and was able to check that those still work on the inverter.

Given the limited time  (1-1/2 hrs a week) that these students have, perhaps, there can only be learning if they are motivated, exploring and thinking on their own. Progress has been slow, but I can feel the progress. Here are some conversations I overheard and had with the students:
1) One student in group 5 telling another - I'm fixing something real, this is one class I really felt I am accomplishing something.
2) Student: Sanjeev we were able to do nothing this class. Why can't you spend more time with us?
Me: Really. You didn't learn to compile code and write into the Arduino.
Student: You didn't help so I had to figure it out by myself. But, that's not learning.
Me: How about what to do with the LDRs?
Student: You just gave us the sensors and asked us to figure it out. We were so confused. We just characterized the LDRs with and without light and know that it changes from 3 kOhm to almost an open. We are not sure how to use it, but if we put it in series with a 10kOhm resistor we get from 1.5 V to 4.5 V.
Me: Ok, do you think it can be better?
Students: We don't know, but maybe if we increase the 10kOhm resistor and lower the lower voltage. This will help the Arduino trigger properly as it needs as close to 0 and as close to 5V as possible. We can't really explain it, can you explain what's going on....conversation proceeds right through snacks break, but they don't care and want to get it right in the next class. I skip snacks too. 

I am having a conversation about design choices (granted simple ones) with Xth grade students from a school catering to village children. Feels like progress to me. 

Finally some pics from my class.

Udavi School Xth Grade Electronics

February 23, 2014

Learning from children...

Having been in alternative education circles I had heard, 'I learnt a lot more than kids than they learnt from me' often enough to wonder if this is an stretched truth. There are certainly aspects like patience, deep listening and learning to look at problem in a different ways, keeping it simple that you need as a teacher. But, is there more?...I sat down to write things that I might have never looked at or learnt if I had not worked with kids:
1) p^2-1 for a prime number (>3) is divisible by 24.
2) Thinking of how to explain p^2-1 = (p+1)(p-1) in pictures.
3) Speaking better Tamil.
4) Experiments with magnets, batteries, potatoes, tomatoes that I had read, but never done.
5) Demonstrating a full wave rectification using only a single probe oscilloscope.
6) A triangle with a chord as diameter always makes an angle of 90' with any point on the circle.
7) Solving algebric problems without algebra and noticing the beauty in such logical solutions.
8) Visualizing fraction additions and subtractions without indulging in LCM.
9) A beautiful method of approximating fractions into decimal (50%, 10%, 1%).
10) Thinking of a simple experiment to understand capacitance.
11) Coupled pendulums and Barton's pendulum that explains resonance without getting to an LC oscillator.
12) Technique to solder properly.
13) Working with Arduino

Of course, there are many things I have learnt about teaching itself:
1) Teaching= 90% Patience+10% everything else.
2) Keep it simple, keep it slow.
3) Importance of presence, mental silence.
4) Making abstract concrete, making concrete abstract.
5) Give something easy, give something difficult, give something to keep everyone busy.
6) Motivation of doing something needs revisiting every once in a while.
7) Keep them interested and place (some) responsibility of learning on children.
8) Don't ask a question if it isn't one.
9) They didn't get it just because you said it. Repeat, repeat.
10) Internalization does not come without practice.
11) One example can lead to interesting generalizations, give more examples.
12) Get children to make their own problems (word problems).
13) Talk math, create situations when children listen to each other.
14) Many children do learn concepts better in their mother tongue.
14) Purpose of education.

and there was clarity...

In one of the many 'examinations' I had conducted, I found that a student was in the zone and her work was just flowing and clear for a three pages. There were no scratch marks, just one thought logically linked to the next, unperturbed by class that was going on around her (they were not all writing an exam). The answers were brief and efficient without the meandering that the mind often does with word problems. I have not seen her replicate the efficiency and clarity she achieve that day, but it was one of those moments that you know something special happened...

One of my Xth class students said he had wondered why I made them work and think on their own instead of working out all the problems on the board. One day, before his term examination, he sat down and tried to work out exercises in the area that I had 'taught' and was able to do the entire exercise in one sitting without getting confused or even pausing. He said he was spooked and  he didn't know what happened to him.

You don't need moments like these to tell you that something in what you are doing is working, but I have to admit they help.

February 02, 2014

test me on what I know...

Towards the end of the term there are examinations in the school and I have been making use of these fully as exercises where children repeatedly work on perfecting their skills (sometimes 'repeating' the exams many times). I have a fair bit of emphasis on application of ideas and word questions vs 'sums' where you are told exactly what calculation needs to be done.

Sha is in 7th grade.and really struggled in the first term. Even in basic calculations he had a lot of gaps. It took me time to unearth these gaps and get down to what his assumptions were that needed to be broken e.g. one day I realized that he is unable to subtract numbers from 100. He knew what is called carry subtraction, but it turned out that he had mostly encountered only up to one digit of carry and 100-95 was pretty confusing for him. He also had difficulty multiplying numbers with 10,100, etc. He would call these fixes 'my method', but over time he has stopped calling it my method and is instead able to use them as his own.

He has some learning difficulties and is quite weak at interpreting English and is unable to get his hands around word problems and is hence unable to solve them. I usually give the kids the paper a week before to take a look at it. This term he insisted that he has mastered all aspects of fractions, decimals their conversations and is able to interpret questions in terms of pizza and even had a feel for it, in terms of pizza slices, but simply could not solve word problems. He felt that he had improved significantly from the first term and wanted to be tested on this improvement.

In the first term the only way Sha could 'solve' something was if each question was preceded with an example. Even through he wrote the 'examination' four times he had attempted the same question again and again without moving to the next one. I wanted to see if there really any change as he seems to indicate though I mentioned that I expect him to be able to figure out what to do and not only do computation at his level. I suggested that I would give him such an examination, but I would need to scale down the result to be fair to his other classmates.He was fine with it.

There was really a marked improvement in what he was able to do (for those who need a score, he got 78/100). He was even occasionally able to find sanity checks in what he did. There were also marked differences in his sheets where he was working confidently and when he felt a little thrown off.

Its remarkable when children start to learn about themselves and understand their strengths without overestimating it...