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Opening the black box of computer memory

These past two weeks, eighteen months of planning finally came together when I

rolled out a new unit trying to open up the concept of how computer memory works with my 8th graders. In talking about lesson planning, I often quote General (and later President) Dwight Eisenhower "no battle plan survives contact with the enemy" - way too often finding that my most thoughtful plans completely fall apart the first time I try to implement them with my middle school students. However I am pleased to report that this is one instance where the learning and engagement far exceeded my expectations and so I'm excited to start to share the idea with anyone who is interested.

This unit grew from a teaching failure I've felt for years. I could take kids through a

great set of lessons that hooked them on the basics of circuits. They could create incredibly fun and complex parallel circuits, switching on / off an almost endless number of buzzers, LED's and motors. I've also felt very successful teaching elementary and middle school students the basic principles of computer coding - using scratch and python to control microbits, edison robots and lego EV3's. But there is this gaping hole between those two ideas - what is happening between the battery and the motor inside that robot that let's me do so much more than just turn it on and off? Last year I created a short lesson that tried to expand on the idea of circuit boards, chips and a little binary code connection to on / off switches, but it didn't produce much more than glazed looks and boredom. Certainly nothing like my goal of creating a sense of awe and wonder whenever my students look at their iphone and ponder how it works. I imagine it was plainly obvious to my students that I really only had a naive understanding of what I was talking about - a problem it was going to take alot more than pretty slides and superficial research to solve.

The solution came to me over lunch - literally a spring 2022 lunch with our school facility director who thought I might enjoy meeting a neighbor, Larry, someone he'd met while sorting out how to deal with dead trees on our school property that were

ready to fall on Larry's house. Turns out Larry is a retired Apple hardware engineer - not just any engineer but the man who for 10 year's led the development of the Ipod from concept to worldwide success. I think I stumbled into a relationship with a genius looking for a project, for as soon as Larry heard about how I wanted to have my kids learn to understand the basics of computer memory and digital data processing he was already sketching what became our first prototype of a single bit memory circuit my students could create and manipulate.

What followed was 18 months filled with countless hours of Larry patiently helping me understand ohm's law, transistors, flip-flops and binary code. He designed single bit memory circuits and a 4 bit accumulator card that can be combined to create a functioning table top "computer" capable of adding and subtracting. Thanks to an

$800 grant from our PTO we had the supplies to build up over 100 circuit boards most o of which Larry whipped out himself in a couple weekends. Last spring we tested those boards with a few classes and their response and engagement was over the top. Not only did they "survive contact", this unit rocked. Literal lightbulbs (ok LED's really) were going off as they learned to manipulate (aka code) their mess of alligator clips and boards to add 1011 (19 in base10) and 1100 (24 in base10) to get 10111 (43 in base 10).

It was great - but there was still a missing connection. It was my 84 year old mother who helped me find the missing link. She loves hearing about things I do with kids, but right after I excitedly shared this new idea she asked "what do they get to make and take with them?" She was right - the core of the success in our Makerspace comes from having kids apply the core concepts to making something. I could justify

that they were getting to make "a computer" with the boards I gave them, but that was really just following my recipe for how to put things together and it was certainly nothing that they could take home. But the question begged another - could 7th and 8th graders really make circuit boards? Many colleagues already labeled me crazy for putting powerful motors with spinning knives (aka drills) in my kids' hands - what idiot was going to give them 720 degree soldering irons and teach them how to melt metal?

A $1500 grants from the Vermont Academy of Science and Engineering (VASE) paid for all the equipment this idiot needed, and so just this past week 50 seventh and

eight graders each created their own single transistor circuit board - one that Larry redesigned so that it actually is a fun maze game. Two pieces of evidence that make we think we nailed it - first was that my supply of ice packs and bandaids was never touched, there was not so much as a single incident with having middle schoolers work with molten metal. The second piece of evidence was I walked into the cafeteria and watched two tables of students hovering over a board with it's proud creator, owners explaining the basics of how "their creation" worked. Who knows maybe the next generation of computer engineers just began their careers.

In terms of learning outcomes, engagement was outstanding and I never heard "Do I really have to learn to solder?" When I compare to the basically zero learning that came out of the 100% talking lesson I'd tried last year it's a smashing success. Is it a 10? - definitely not yet - maybe a 7 or an 8? This flipgrid video assessment by one of my 7th graders is pretty typical of what I got from everyone - and it highlights several gaps I want to fill - mostly in the area of electrical flow through the circuit and how the transistor is the key with it's ability to shift flow through voltage variations. Their assignment was to explain "what did you make, how does it work, and what problems did you solve?" Definitely making some jumps down the journey to understanding how and why a transistor is such an amazing invention. Understanding that is critical to how a combination of

transistors (aka a computer "chip") can create our on / off circuit for storing binary data. But that feels really accessible now that they have this game / tool right in their hands, something that, in the perfect learning world I dream about, they might even pull out and try to explain to someone else. Next week we'll continue with the

lesson we already created last spring, connecting sets of these and expanded iterations to build our binary computing circuit. I'm pretty confident that will seal the deal to achieve that initial target of opening up the black box of a computer's memory.

I won't pretend that this will be an easy project to replicate, in fact there are several elements that I still barely understand and can only make happen with our resident genius Larry's help - such as the creation of a gerber file to guide board production

at JLCPCB factory in Shenzen, China or the logic behind the 4 bit accumulator circuit board schematic. We also have invested over $2500 to get things to this point, a big chunk of any makerspace budget. But I also can't imagine I'm the only STEM teacher trying to open up the black box of computer memory and so I'd love to hear your thoughts and ideas. Maybe together we can bring a new idea to life or offer enough support to help you recreate your own version. Just reach out at and let's see what we can do.

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