Digital Logic at the Side of the Everlasting Why...


After meeting some folks from San Francisco’s Tinkering Studio here in Seattle, we sent them either a present or a curse (we’re not sure which). We sent them a package containing instructions and all the parts to build three of our digital logic boxes. Poor Ryan apparently selected the short straw

Building the kit was a good experience, but for me I wanted to mess around with something more basic and easier to understand. I looked up logic gates in Forrest M. Mims III circuit guide books and found a simple diagram of the “and” and “or” switches. I used two momentary switches and constructed two circuit board blocks that could be combined with the rest of the set. However, I am still a little unsure of the “why” behind doing this activity. While programing and systems thinking are interesting topics, I wonder what the intrinsic motivation for people to play with them could be.

Ryan is exactly right. And here is our explanation(ish):

While we recognize that systems and computational thinking may or may not be interesting in themselves, we see them as potentially valuable tools to help us think about our own thinking. All the complex ‘thinking’ computers do can be broken down into a long series of very simple binary 'decisions’, which are basic rules (logic) governing inputs and outputs. Understanding those rules helps us understand how computers 'think’, and understanding how computers 'think’ can help us better articulate (in every sense of the word) our own complex thinking. Essentially, the computer-as-series-of-logic-gates serves a metaphorical function. Just as the chain reaction machine might.

For us, the purpose of putting the logic gate into a black box (of sorts) was to create a puzzle. You know that inside this box is an AND, OR, or NOT gate, and your job is to figure out which one it is. In that sense, the motivation behind the activity is simply problem-solving and is not much different from that which motivates us to solve any other simple puzzle. The tool we offer to do this—the truth table—is simply a way to document the problem-solving process. All that said, we are working to make the problem-solving portion (including the truth tabling) more inherently fun. We want to keep the language ('input’s, 'output’s, '1’s, '0’s, etc) because we think doing so will help provide a foundation for those who want to learn more about computers. But we want to make it more tactile, if possible.

Once we get the basics of how to figure out which gate is inside which box, our next challenge is to connect the gates together to see if we can predict what the output would be, given our inputs. For instance, when we connected the AND and NOT gates together (essentially creating a NAND) at GeekGirlCon this weekend, we asked participants whether they thought the output light of the NOT gate would be on or off if we turned on both AND inputs (for instance). At that point, we’re increasing the complexity of the puzzle a bit—we’re creating a hypothesis and connecting that hypothesis to specific conditions. After they articulated a hypothesis, they then tested it. And if their hypothesis was incorrect, they would then go back and figure out exactly where their thinking had gotten off-track.

Eventually, we want to create an obstacle course (of sorts), where we have an end goal (such as, turn output ON) and certain requirements (such as, use at least 2 logic gates) and see what we can get out of it. We also want to combine our digital logic activity with our binary counting activity to see if we can create and interpret the output of a single bit adder. By using the language and rules of digital logic, we are simply adding a bit of structure to a seemingly complex problem-solving process. Once we have the method down, we think it can be highly portable to a variety of challenges and easily built upon. That’s the goal, anyway.

The broader point is that we have a tough time articulating the answer to a question that our Big Brains ask all the time (when they’re doing their math homework, for instance): “Why?”. It’s important for us to have a 'why’ for everything we do and everything we ask our Big Brains to do, and yet, it’s incredibly challenging to make that 'why’ clear throughout the process. Especially when the task is foreign or complex, if our Big Brains can’t connect it to something they already understand, the experience or knowledge they gain from it is not going to stay with them for very long. Articulating the 'why’ is probably the toughest aspect of instructional design and also the most essential to get right. Which means we have much more work to do.