Design, Build, Reiterate, and Light It Up! - Circuits and Engineering

This has definitely been the hardest year I have ever experienced within my 15 years of teaching middle school students, and I am sure it has been just as tough if not tougher for the students. I have always been a big advocate for minimizing screen time for young (and old) minds but it sure seemed like screen time was the only option over this past year and continues to be a big part of our daily teaching schedule. Well, to be blunt, I had enough. We finally had students in our classes, albeit not all of them, and I needed to get my hands on a project... as I am sure the kids did too! This was ultimately a project of necessity and it fit perfectly with what both my students and I needed. The goal of the project was for students to identify the difference between parallel and series circuits and to incorporate a parallel circuit into their own design. Their design could be anything from a pair of jeans they wanted to make light up, a Mother's day card that lights up, a box that lights up, or pretty much anything else that piqued their interest. Very few of the students had much experience with circuits and not one of my 100 students had experience with parallel vs series circuits, so there was some preliminary lessons and demos that had to happen prior to the engineering project. I want to go over how we got to that point but before we do here's what I was working with:

Student Group: One-hundred 6th and 7th Grade students (ages 11 - 13)

Time Frame: Three weeks from start to finish

Goal: Recognize, build, and test both parallel and series circuits to model how electricity flows along a circuit.

Supplies: See list below

Supplies

1- Copper Tape ($7 and we ordered 3 - We originally ordered this tape but we found it not very conductive on the adhesive side)

2 - LEDs ($13 each and I ordered 2) - $26
3 - Button cell batteries ($7 each and I ordered 6) - $42

4 - Resistor Assortment ($17 one order was enough) - $17

Hot glue guns

Lots of cardboard

Brass fasteners

Other random stuff to use in the student's designs

Step 1: Teaching the Basic Concepts of Electricity and Circuits

Most of my students had had some experiences with discussing circuits in previous years (4th and/or 5th grade) but it seems like very few if any had any concept about what electricity really is. I decided to take a very simplistic approach to teaching my students about electricity to start. Here is what I started off with (please don't mind the simplicity in these "definitions")

Electricity - Energy from charged particles (electrons in our case)
Circuit - A closed conductive path allowing electrons to flow from one point to another
Voltage - Electrical potential
Current - The flow of electrons along a conductive path
Resistance - The opposition of current flow in a circuit

From there I used the tried and true analogy about electricity being a bit like a river running over a waterfall where voltage can be represented by the height of the waterfall and the amount of water running over the waterfall can represent the electrical current. The higher the waterfall the more potential energy there is between the top of the waterfall and the bottom (more voltage), the lower the waterfall's height the less potential. With more water running over the waterfall there is more individual water molecules cascading over the top (more electron flow... more current), less water flowing means less current. I then use the explanation that you can have a really high voltage like when you shuffle across the room and touch a door knob and get shocked (that's over 1,000 VOLTS!) but since there is little current (very few electrons) you don't get fried... although you do get a nice zap. It's a very different scenario with low voltage and high current situations. A welder for instance might only use 10 - 30v but output nearly 140 amps... that's going to be a lot more than just a mere zap. This topic always leads to some great discussions and lot's of drawing things on the white board (remember those things?). Resistance can be looked at as a constriction in the river before the waterfall that happens to prevent less current (and voltage) from flowing over the waterfall. The greater the constriction... maybe a dam, the less the water there will be as it topples over the waterfall.

I made bags of materials for the students to begin their adventures with circuits. The bags included the following:

(3) 3v LEDs
30cm of copper tape
(2) resistors of different values (I used a 50 ohm and 150 ohm)
(1) brass tab

The students put their names on the bags with a sharpie and this will be a good storage space for their materials later on down the road with the engineering design project. The first thing we had students do was to make a very simplistic circuit by simply running copper tape along the edges of the card (they should label that line negative) and then taping down the negative side of the battery to the negative line. We then connected the negative leg of the LED (the shortest of the two legs is negative) with some copper tape. We then taped down the positive leg of the LED (the longer leg) to a piece of copper tape that was not at all connected to anything. You can then fold out the brass tab and use it as a intermittent switch to close your circuit. Explain to the kids that an open circuit doesn't have electrons flowing through it but when you push down on the conductive brass tab and make a connection between the positive side of the battery and the LED you are closing the circuit allowing electrons to flow through the circuit. Of course there needs to be a discussion about those previous elements of electricity to give a full picture.

We'll talk about the interactions of these three elements; voltage, current, and resistance in a bit, but for a minute we'll shed some more light on circuits with an online circuit builder...

Step 2: Gizmos to Model Circuits

Our district has a subscription to the online labs / explorations from www.explorelearning.com called Gizmos. There are a few circuit building activities that they have available with the gizmos. You can try them out for 5 minutes for free, which might be enough to give the kids some time to explore, or you can get a subscription to the programs. We had the subscription due to the online/hybrid/in-person/what is this school year we have been all so much enjoying (note the sarcasm). Whatever the case, the gizmos are great and I have been using to varying capacities for the past nine years or so, sometimes with a borrowed subscription.

Give the kids a good hour to explore with the circuits. You can make your own worksheets to guide them, give them completely open time to play with them, prompt them with a question, or simply use the provided worksheets and guidance provided with the Gizmos. What should the kids get out of this exploration?

They should recognize the difference between insulators and conductors
They should be able to identify the difference between a closed and open circuit
They should be able to see how varying the voltage and/or current changes the luminosity of the light
They should be able to see that a switch is used to both open and close a circuit

Okay, so they kids should totally get what a circuit is and how it functions, now you need to provide them with the key details to building each type of circuit that will be used with this project; series and parallel circuits.

Step 3: Comparing Parallel and Series Circuits - Making the LEDs Light Up

Let's get this right out there, because it's important- You don't typically use parallel circuits with LEDs. They just aren't manufactured to exacting standards and you will ultimately get brighter and dimmer LEDs in the same array. Also, from what we learned through our exploration, mixing LEDs of different colors is a big no-no. The blue, white, and green LEDs supplied in the supplies list at the start of this instructable are all 3 - 3.2v LEDs. They can work at lower voltages but will be much less bright, and they can work at higher voltages but will be very bright... and very short-lived. The red and green LEDs in the pack are 2 - 2.2v. Keep driving this most important of all points into the kid's heads - "Electricity will take the path of least resistance". With this in mind you can see why with a mix of LED colors only the ones with the lowest voltage are going to light up reliably. The red and green LEDs require less energy therefore they are the path of least resistance. They will glow brightly while the blue, white, and green LEDs will likely not even light up. You could use Ohm's law (more on that in a bit) and determine what resistors you need to use on the lower voltage LEDs, but I can tell you that it's an act of futility, and exhausting with students. So, with this in mind, it's time to talk about how we might accomplish a couple of ideas.

Series Circuits: In a series circuit the loads (in this case LEDs) are wired in a chain with the positive of one end touch the negative of the next and so on. The positive side of the battery would be connected to the positive leg of your first LED, then the negative leg of the first LED would connect to the positive leg of the second LED. This pattern would repeat until you come back around to the battery for a full circuit with the final negative leg of the last LED touching the battery. A series circuit requires enough voltage for each individual LED. Therefore if you have four 3V White LEDs in the circuit you will need approximately 12V to power all of them at their full potential. We were working with a single button-cell 3V battery, so a series circuit wasn't in the cards for us. Which brings us to...

Parallel Circuits: In a parallel circuit the loads (LEDs) are wired so that all of their positive legs are connected to the positive side of the battery and all of their negative legs are connected to the negative side of the battery. Assuming that all of the LEDs are exactly the same (same voltage, same current requirements, same internal resistance) each will receive an equal amount of current from the battery, something like this. Sadly, this magical equilibrium amongst the LEDs is not going to happen (at least with the quality LEDs we are buying). Even LEDs with the same color are going to have some variations in their internal resistance. And, if you remember, electricity will take the path of least resistance! Therefore the LEDs with the least resistance will be the ones to light up for you while the other more resistive LEDs might not even give any indication of glowing at all. Nonetheless, a parallel circuit is our best bet to keep this project affordable and give the kids a chance use multiple LEDs... even if it's not the most reasonable choice for longevity sake.

With all of this in mind your student's heads may be spinning. A basic explanation of the interactions of voltage, current, and resistance might (MIGHT) help them out... cue Sir Mix a Lot

Step 4: Ohm My God Look at That Current! - Understanding LEDs and Using Ohm's Law

Ohm's law states that voltage is equal to the current multiplied by the resistance. You can mix this up just as you would do with any formula with three variables. Current would equal voltage divided by resistance and Resistance would equal voltage divided by current. The letter "V" represents voltage, "R" represents resistance and "I" represents current (look up why it isn't "C" it's an interesting story). Typically you will wire a resistor in series on the negative leg for each LED. This LED will protect the LED from having a premature death by allowing only the proper current to flow through it. To figure out the resistor you will need to use you will have to know the voltage of your battery and the voltage of your LED. You will be trying to make up the difference between the battery's voltage and the LED's voltage. So, if you have a battery that provides 3v of electricity and an LED that requires 2v you have a difference of 1v. Using Ohm's law we can then calculate the correct resistor we would need to use by taking the voltage (1v) and dividing it by the current (our LEDs use 0.02 amps) which would give us a 50 ohm resistor. Your bundles of resistors might not have the omega symbol to represent ohms but might substitute the letter "R". If you see a "K" that means kiloohms (thousands of ohms) and if you see an "M" that means megaohms (millions of ohms). Want to speed up the math and do more complex calculations? Try this calculator out, it works great!

To model the effects of using different resistors with two LEDs I made a little board to show how no resistor, a 100 ohm resistor and a 50 ohm resistor affect the brightness of the LEDs. In the picture above the circuit with no resistor wouldn't light up completely (only the red would light up - path of least...) and the other two circuits had both their LEDs lighting up, albeit at different brightnesses.

So, I am colorblind. Resistors have tiny little painted color stripes on them that tell you what resistance they provide. Suffice to say, I can't tell a dang thing by using charts like this because I can't really see the colors all too well. I wish there was a machine that could tell you the resistance of these tiny little things without having to read the chart. You know, something that passes a small current across the resistor and does the Ohm's law thing on its own...

Step 5: Using a Multimeter With the Project

Hey there is one that does that and so much more! I have three of my own personal multimeters that I use around my house. I have three because I use them all over the place and seem to always be reaching for one whether it's because I am building a new electrical rig or because my truck's battery is dead (yup, that was this morning). A multimeter measures ohm so many different things (sorry, that pun will not die). I am not going to do a bunch of typing here, instead I made a nifty little sheet with the main functions of the multimeter that you can use to help orient yourself with this most amazing tool!

The kids loved using it and it was indispensable for checking the continuity of their circuits. They kept calling it the beeping thing (which made me laugh each time since it sounds like they are calling it a swear word). You don't need to find the best of the best when it comes to using a multi in the classroom. Get some affordable ones that do the job and if you can get at least three for the class that number seemed to work for 20+ kids in the room at a time.

Step 6: Modeling Some Basic Ideas and How to Use Basic Office Supplies to Build Switches

These concepts are pretty new to most of the kids. Even if they did tinker with circuits earlier on in their schooling I am certain that it wasn't this open ended and was more of a "circuits kit" to give them the basics. We are going to be taking something that they just recently learned and incorporate it into something they are going to build, using inexpensive household materials nonetheless! It's not a bad idea for you to get acquainted with how electricity and circuits work and making a few basic models is a nice way to show the kids that you are invested into this project too and that you are going to be able to help them as best as you can to be successful. I decided to model something that many of the students would be interested in incorporating into their project, switches. A switch is basically a break in the circuit that creates an open circuit and when initiated creates a closed circuit. It can be as simple as a flap of paper that closes on top of the positive side of the battery completing the circuit to as complex as a knife switch that works by throwing a lever. All of the switches in the pictures above were built using easily obtainable household/school/office items such as popsicle sticks, brass tabs, bottle caps, hot glue, cardboard, and tape. Your switch should have two legs to it, one connected to the battery (positive or negative side, it doesn't matter in this case) and one connected to the LED (make sure if you pick the negative side of your battery the other side of your switch connects to the negative side of your LED). All you need to do is allow the two legs to touch each other in some way allowing the circuit to close completely. I kept the pictures in order so that you can see how I set up each of these four different switches. Send me a message if you need more of an explanation but first try to figure it out on your own, it's a lot of fun building these and the kids think you're a wizard at first until they try it and are successful too!

Step 7: Creating Excitement Around an Engineering Design Challenge Incorporating Circuits

Like I said earlier, it's been a truly unorthodox school year and I think these kids have had enough screen time to last them for the next twenty years! They really embraced the idea of using their hands and building something but I still wanted to make sure that I could get them extremely excited about the upcoming project. I told the kids that they are given the challenge to design a project, ANY PROJECT, that incorporates a circuit into it. I really wanted kids to come up with their own ideas and I knew that if I provided them at least some sort of a foundation that they would be able to take control of it and build from there. I provided them with this list of ideas to start which I hoped would get their minds whirring. I can honestly tell you that it did and what they created was far beyond what I envisioned.

I had students start with brainstorming some ideas and thinking about how they would complete each of their ideas. From there I had them select one single idea to work with. I had them do a one to one drawing of the plan so that they could determine how much of each material they needed and then I had them complete this Order Form so I could get their materials gathered up for them.

Step 8: The Building Process

Students worked directly off of their plans and I didn't hold them tight to their original materials lists they created with the order forms, knowing darn well that they would need more copper tape and different resistors and the such. I didn't want to dampen their creativity by limiting them for something silly like that. The order form was a great example of how to determine the basic materials you might need to complete a project though and therefore it is still an important component of this project.

I provided students with a few different tools to build their projects:

Dremel / rotary tool with angle grinder / cutoff wheel
Hot glue guns (lot's of em!)
Box cutters
Exacto knives
Rulers
Clamps (spring and sliding)
Other odd bits and pieces

I am not going to lie, the building process is tiring for you as a teacher. You will hear a lot of calls for help from the students, but each one is a chance to teach them another lesson in problem solving. This is real learning, real excitement, real teaching, I LOVE IT!

We did about two school weeks of building for this project but I can honestly say that they gained two months of education from the process.

Step 9: Final Results!

I am going to let the pictures speak for themself here and hopefully my student's creativity give you some inspiration to do this project with your own classes. I can tell you that the kids came into each day excited and energized and they continuously kept telling me how much they loved the project (that warms your heart as a teacher).

Give me a shout if you have questions or comments and please give this project a go, you and your students will love it!!

PS: We did a "Grand Viewing Gala" to end our project where all students were allowed to vote for their three favorite creations. This was an absolutely awesome way to end the project and really pumped the kids up. I used a bunch of instructables swag I had won a few years back to create prizes for this.