Play - Doh Logic Gates

Still working on Logic Gates in the Cs Principles class. Today they constructed logic gates using play-doh.

OR Gate

We started we watched this video connecting logic gates, AND and OR gates to binary numbers.

Before we did the logic gates I gave them a few challenge problems. I gave them a truth table and they had to construct a logic gate to produce the result. We used the logic.ly website to demo. Want to try one? Here you go:

Then they made logic gates with play-doh. The materials are fairly cheap. The most expensive part are the batteries and the battery holders (these run about $3). The good news is this activity works well with groups of 3 - 4 students, so you don't need a lot of these.

Materials:

• Play-Doh 
• LED lights
• Battery Holder (I use rechargable AA batteries)

I personally do not use the insulating play-doh. I am sure it would be helpful, but I barely have time to cook dinner for my own kids this week, much less make craft supplies.

I left the instructions very open ended. Each group got two battery packs, an LED and some play-doh. The instructions were to make an OR and an AND gate, and take a picture of each.

Post on PlayDoh circuit Ted Talk

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Pinterest and Teaching Computer Science

Spring is here. I know some of my teaching friends to the north are still getting the occasional snow but for us it has been sunny and in the 80's. 

I love the end of winter, but as a teacher it is a mixed blessing. All the sudden you are fussing about the lengths of their shorts and trying to keep them somewhat focused on what's happening INSIDE the classroom.

So if you are in need of some inspiration here is my Pinterest board where I keep track of ideas that might apply to computer science.

Drawing from our sidewalk chalk last spring.

My favorite idea of the last year was doing sidewalk chalk to do algorithms and pseudocode. Will I ever make homemade sidewalk chalk? Probably not, but the recipe is there if you get the urge.

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To Make a Program you Have to Break Some Eggs

One of my favorite toys in computer science are plastic eggs. Cheap and they can be used to teach so many things. We are working on searches and sorts in the APCS class right now. They also work well when doing algorithms in the CS Principles class.

To start with searches and sorts I use plastic eggs filled with fish tank gravel. Email your faculty and parents - I guarantee you can get these for free. Fill the eggs with varying amount of gravel and tape them shut. Better yet have a kid do this. You are busy.

I let the kids pick a partner and each pair gets 6 or 7 eggs. Please do not forget to explain that the eggs do not have candy in them. I didn't do that the first time we did this and it made for a very disappointing mess.

Have them put the eggs in a row then "search" for the heaviest egg. Write out the steps you followed.

On the board I then do:

int eggs[] = new int[6];

This is in the APCS class, in CS Principles I make this less formal since they will be doing this in Scratch.

I have the kids come to the board and write out their algorithm, in Java in the APCS, pseudocode in CS Pricniples, using this array. Bam! They just all created a Linear Search.

So, why eggs?

I used to do this writing numbers on the board. They watched and I did. It is always better when THEY do. They are going to remember the Linear Search much better if it was their idea in the first place. 

Also, when you do numbers the amazing processor that is the human brain can just scan the list and pick the biggest. No problem. 

But a computer cannot do that - it cannot just look at a data set in aggregate and pick one. It must "touch" every piece of data in the set and make a comparison. Which is exactly what the kids do with the eggs. Point that out, they should know that.

This is also a good time to go over swapping. They get so confused on this.

How many times have you had them try to swap two numbers and they do:

a = b;

b = a;

Here is the fix: Hand each group some cups - make it look like you are giving them an arbitrary number, but make sure they all get at least 3.

Rule - you can only have an egg in a cup. NEVER can you have two eggs in a  cup. Now swap two eggs.

Again, once they get the point of using a third cup, you have them write out the algorithm in the language of your choice.

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Weekly Roundup - Computer Science Surfing

Some Computer Science websites I've been looking at this week:

• Little Bits these kits let you build circuits. They snap together with magnets. When we cover conditionals in the CS Principles class we also do logic gates and circuits. This could be a fun way to visualize this.

• Ted Talk Andrew Blum. What is the Internet Really? We're just finishing up our Internet unit in CS Principles. Monday is our last day before break and this will be a great way to finish up the whole thing.
• While you are at it you should really read his book: Tubes . My fantasy field trip at this point is to go to Northern VA and visit the parking garage he mentions that housed the early pieces of the Internet. Then we'd have ice cream, because sometimes that's what it takes to make a parking garage exciting.
• Ada Lovelace Video - Her birthday was on Monday. This video is the best explanation I have found about why she matters. The kids seemed to like it to. It is always a good sign when they 1) watch the video without trying to sneak in a round of Bloons Tower Defense and 2) ask questions after it is done. Score on both counts.
• Also on Monday Google did a Doodle of Ada. As always, Google helps make it relevant.
• The rest of the video series also looks great - covers everyone from Alan Turing to Hedy Lamarr.
• Also: Good article about Facebook Interns on why CS is a good choice.
• Also, if you are feeling crafty - This site has templates for Star Wars snowflakes.

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Paper Robots

We're doing a little crafting in the lab today.

(Source: Next to Nicx)

My CS Principles kids are plugging away on their Internet Portfolio papers. They have chosen some very interesting problems to write about. We are also doing the CSS section of Code Academy. My plan is for them to do a web page about thier paper to present their solutions.

A few of  the kids have gotten ahead. On the paper, and the CSS, they even have done all of the Ruby stuff in Code Academy.

So we're making paper robots.

• Paper robots advent calendar
• Paper Toys

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My Secret Obsession

I have a thing for elementary classrooms. While the idea of teaching the 12 and under crowd is in no way appealing, all the projects and circle time really sound fun.

Here are a few of my favorites:

This one we have used already this year. It is great for doing Octal and Hexadecimal numbers. It really gets the point across that hex and octal are a more compact way of storing large values. When you pull the cups apart you have the number written inside...I'll try to post a picture of the Hex-Cups to make that clearer.

We already do the Analog-Binary Calculators - which my kids call Flippy-Dos, so the cups have become Roley-Dos. And seriously - the flippy-do is the easiest way to show twos comp for negative numbers.

This would be great for showing the sequencing of code. My beginning students have a hard time sometimes getting the ordering of the commands. This could be a fun way to demonstrate how important the order is. They could work in pars with a whiteboard and follow each other's commands.

This project maps where a student is in their community. This is my next project for the CS Principles course. One of the my goals for the students is to understand that the Internet is a physical thing. My plan is to do these showing where they are on the Internet. They would be on the small circle in the middle - and then the structures that make up the Internet are on each of larger circles moving out.

This is a review game - the site includes the cards for the pockets. This would work well for AP style problems

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Weaving Binary and Peeing in Buckets

Weaving! Today was craft day in CS Principles. We are starting binary numbers - and if you think weaving in a computer science class is odd, I'll have you know that one my favorite computer science book ever was A Computer Science Tapestry by Owen Astrachan. It totally relates.

I borrowed a frame from our art department and set up the warp using this description:

I used cotton for the warp and wool for the weaving. Using a  needle and thread I got us started, then we passed it around and everyone took a turn:

So, why weaving in computer science? Binary is the mast basic way of communicating weaving and knitting patterns. Think knit - purl - knit -purl. In weaving it is over - under - over - under. Alternating rows of over - under gives a small checkerboard pattern. By changing this we get different patterns in cloth.

Houndstooth Pattern

This brought on a whole load of questions, and we did get off topic a bit. One kid brought up that the Romans used urine to dye fabric...and in fact To dye animal fibers you need an acid to fix the color to the fibers, which is why Kool Aid can be used to dye hair, or wool. Uric acid was the first commercially available chemical. Long time ago folks used urine to do indigo dyeing, which meant collecting a lot of the stuff. In a bucket, in the barn.

We did finally get back on track and watched a video on Jacquard Looms. I know we always use the examples of punch cards coming from looms, but really who cares? Today was the first time in all the years I have taught this that it mattered at all to the kids. Doing the weaving first made them really ask a lot of good questions about the loom. And the idea of storing a pattern and algorithm in a binary system is the basics of everything we do.



The final Product, it's a bit lumpy, but it is made with love.

They really got into this and had lots of questions. Had I known I would have set everyone up with a loom so they could make their own. Might be an interesting extension to give them a pattern in binary and see what the design ends up being.

After the weaving we started on binary numbers. Last class we spent about 20 minutes doing an activity covering how base ten numbers work. Today for the fast start their question was "if you only had 1's and 0's to represent numbers how would you represent 0, 1, 2 and 3?" Lots of good debate over how to show certain numbers.

Last we made our Analog Binary Calculators that we'll use the next few classes as we go more in depth on how binary works.

Thirteen!

Update: Here is a post about the weaving program at the Henry Ford Museum in Michigan. I got to see the Jacquard loom in action last summer when I was there for Maker Faire.

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Computer Science Unplugged

While looking for some computer science related videos for the last week of school I found this: cs unplugged video.

65 minutes of awesome. Not only does it have some great explination of computer science, it shows some great modeling of how to use the cs unplugged techniques. If you have never tried cs unplugged you really need to give this a look.

There is a list of shorted clips here.

My favorite quote: "Computer Science, it's just science, computers are just the tool".

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Play Dough

We will be doing this:

This Ted Talk covers using conductive play dough to make simple circuits. I am trying to think of a way to work this into doing logic circuits.

I might be over thinking it...the best approach might be to hand the materials to the kids and tell them to design the gates, and see what they come up with without my help.

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Sidewalk Chalk

Quote of the day: "It was one of those fight or flight things, and you can't fight a mouse." 12th grader explaining why he ran from a mouse.

We had a four legged mouse in the lab today, tiny and cute, but it's gotta go. The kids have already named it Billy and want to keep it.

Considering this week started with 7 inches of snow and today it is 80 degrees they have been a bit off the walls, even without rodents.

So, for the CS Principles class we went outside today. We've been working on Algorithm design (Big Idea # 4). To work on this we did sidewalk art. each team was given a copy of a lab we will program in C++ next month, and using pseudo-code they had to plan out a solution. We haven't done ifs or loops in C++ yet, but they all came up with a correct algorithm for solving the problem.

We started this fall with BYOB Scratch, and they seem to be doing much better this year with using methods in designing their programs. They all got exactly how to call existing methods to find the solution. I am looking forward to seeing if how their labs compare to previous year's students after drawing out their plans.

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Simon Says - Recursion!

Spotted this today - they are reissuing Simon Says. The interface reminds me a lot of the Siftables that were designed at MIT. 

Not only are these just plain awesome, the old Simon Says game is a great way t teach the concept of recursion. Can you say QUEUE?

 

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