Circuit Masters

Last year I introduced my 5th graders to the joys and wonders of physical computing, using a computer to program the behavior of components likes LEDs and buttons. My hope then was to eventually push physical computing down to 3rd, or even 2nd, grade. This unit sees the 4th graders take the next step in their computer science learning journey.

Students started by learning to use a breadboard, LEDs, resistors, jumper wires, and batteries to build simple circuits. Electrical circuits are not new to 4th graders, having covered them in science class already. However, these particular components are. We identified each part, discussed its function, and went over the proper handling of each. Students were then guided through building a complete circuit. As always, when that first LED blazed to life, the room was filled with gasps and sqeals of delight. (That NEVER gets old for me.) With one LED in place, the teams immediately set about adding more.

Having gotten them comfortable with the breadboard and other components, I introduced the tactile button. We started with a short overview of how the button works and compared it to the switches they had used in science class when studying circuits. So far they have all done well recreating the first day's circuit with the button from the notes in their journals. They also have thrown themselves enthusiastically into the challenge of controlling multiple LEDs with a single button. We wrap up these first few days by identifying the differences between series and parallel circuits, both of which they have now built and recorded in their notes.

Using a switch or button to control the flow of electricity is a mechanical process and something of a review for 4th graders. Memories refreshed on the topic of circuits, we moved into the substance of the unit, physical computing. In the lab we are fortunate to have 10 Raspberry Pi computers. Each is equipped with 40 GPIO pins (General Purpose Input/Output) and it is these that make physical computing possible. Students began with a basic introduction to the Pi and how it like a regular PC as well as how it is different. Among the many languages available to students on the Raspberry Pi is a version of Scratch with an extension that allows for physical computing. For the first day, so that they could focus on programming, and not on juggling LEDs and resistors, we used an add-on board called Traffic HAT. It has 3 gumdrop sized LEDs and an adapter that fits neatly over 4 of the pins on the Pi and greatly reduces the time it takes students to get to blinking lights. I am so proud of how the students have been working together to debug when programs don't work as expected. The best thing to see is when one team gets the lights going in some wild pattern and calls across the room, "Woah! Look at that!". The inevitable response is a chorus of, "How did you do that?". Soon the room is full of the sounds of genuine engagement as teams call out programming tips to their friends.

Students complete the unit by learning to use the breadboard and other components with the Raspberry Pi. First they add a button to control the start of the light sequence on the Traffic HAT. This usually proves harder than most of them think it will be. Again, there is lots of cooperative debugging and problem solving. With that task accomplished, they use LEDs, resistors, and buttons and experiment with programming the components to behave in different ways. This generally becomes an exercise in making the lights blink as fast as possible in the greatest variety of patterns.

This has been a fun unit and I am looking forward to next year with this group and pushing their digital making skills to the next level.