Intro: Circuit Blocks in the Classroom
This is part of a series of Instructables intended for teachers about educating students in the classroom around making and tinkering. For more about the details of this project, check out our blog.
Learning about circuits and electricity can be an intimidating task - it seems so complicated! This activity involves the use of a modular set of electronic components that are easy to hook up to each other - like LEGOs for circuitry. In this Instructable, I will assume that you have already built the circuit block set and have a few of the basic components - battery, motor, knife switch, momentary switch, LED, speaker and potentiometer. The circuit combinations possible with a few of these components are almost endless, and any electronic component that you can glue onto a block of wood will work - take apart some old toys and add some of their working bits to this set, for example.
For full instructions on how to make a set of circuit blocks (or add new ones), visit this Snapguide from Learning Technologies at the Science Museum of Minnesota.
There is also a commercially available set of modular electronics called Little Bits. They are a great educational tool, but their downsides are that they are very expensive and not quite as durable as one would expect. Plus, you don't get to make them, so where's the fun in that!
Step 1: Materials Needed
You'll need the blocks shown above. Here's a brief description of what each does:
- Alligator clips - used to connect each block to other blocks in the set. Any will work, the ones shown above were made with thicker gauge wire (16 AWG audio speaker) and larger clips for durability. The test leads you can typically get work okay, but kids tend to destroy them rather quickly.
- LED block - made from a string of LED christmas lights. Ensure that the + and - legs are labeled properly on this one. LEDs are a diode, which means that the electricity has to flow through them the proper direction - the + has to be attached to the positive side of the battery and - to the negative side.
- Potentiometer - this is a variable resistor. When the resistance is high, less electricity is flowing through the circuit. When lower, more. So, when the volume is turned all the way up on a speaker or speed on a motor, the resistance is lowests. When the speaker has the lowest volume or lowest speed on the motor, the resistance is at its highest through the potentiometer.
- Piezo speaker - this is a little buzzer. Make sure for this project you are using the one that is NOT labeled "ED" - those are for a different project and Instructable I will link to. These, like the LEDs, need to be hooked up with + to positive and - to negative.
- Battery - plain enough, this powers the whole thing. See a later step, but DO NOT short circuit the battery for too long (connect the two terminals directly to each other) or it will heat up a bunch and start smoking!
- Motor - a little DC motor. This can be hooked up either direction - changing the polarity of how it is hooked up will change the rotational direction of the motor, a great experiment to do with these kits.
- Knife switch - looks like something right out of Frankenstein! These switches are a way to hook up two separate components to the same battery, or just make a on/off switch that stays on/off for a component. See a further step in this Instructable for how to hook it up.
- Momentary switch - this is a simple pushbutton switch. When it's depressed, it allows current to flow through the circuit. When it is not pushed, it breaks the circuit. A great setup to do is put it in line with a speaker and have the kids make morse code.
Step 2: Safety - Don't Short Circuit the Battery!
Two safety considerations to keep in mind. First, as above, NEVER make a circuit that doesn't have a load on the battery (LED, motor, speaker, etc) - this is short circuiting the battery and will ruin the batteries, potentially causing them to overheat and smoke. It's unlikely they will catch on fire but it is possible. A switch (momentary or knife) is NOT a load on the batteries, so hooking this up between the two terminals is like what is shown above. If the batteries do get shorted, disconnect them immediately and set them aside for a bit. If they remain that way for too long, the batteries will become unusable so throw them away.
The only other real safety consideration to keep in mind is that the motor spindle can get caught in someones hair or pull a string on their hoodie, etc. I did have one kid attach some tape to the spindle and get a girl's long hair caught in it, so just monitor this setup when applicable.
Step 3: Circuit Symbols
A great extension to playing around with and building circuits in this activity is learning about circuit symbols and diagrams. Electrical engineers and hobbyists all use circuit diagrams to be able to replicate someone else's circuit - it's an almost universal way to communicate how components are hooked together. Circuit diagrams scale from showing how to hook up something as simple as a light bulb to as complex as how to build a supercomputer.
Each component should be labeled with the internationally recognized circuit symbol - that way, you can set out a diagram and challenge the kids to set up the circuit using the symbols to see what it does! The above .pdf has the symbols for all of the components in this Instructable as well as a few example circuits to get you started.
I created my diagrams by building a circuit on Tinkercad, and exporting the diagrams to a word document to then print off. Other free programs like Fritzing are a great way to do this as well, and are useful tools to learn about electronics in general.
Step 4: Beep Beep Boop...
The above circuit is a great way to get started. A momentary switch and any of the load components (speaker, LED, motor) will allow you to switch on and off the current to the component. Make some morse code. light up a dance party, etc. Hook up multiple components in line with the battery and see what happens when more of them are powered on.
Step 5: Pump Up the Volume!
Play with the potentiometer. This component changes the resistance through the circuit - higher resistance impedes the flow of electricity, making the light dimmer, motor slower, or speaker weaker. Lower resistance allows these components to work at a higher brightness, speed, or volume. What happens when the resistance is all the way up?
Step 6: The Knife Switch
The knife switch block tends to give kids trouble, and it is not immediately intuitive as to how it is hooked up. Basically, it connects the middle contact to either of the two side contacts. See above for how to make it power two separate blocks. You can alternate between the two by putting the knife down on either contact. Multiple components can be added in series or parallel on either contact.
Step 7: Series and Parallel Circuits
The concept of series and parallel circuits is a fundamental one to get across to kids. How batteries are hooked up to a circuit changes their output voltage and current, which has an impact on how the circuit will behave. The same goes for components - if they are hooked up in series vs. parallel, they will behave differently. The above video goes into depth about parallel vs. series. The typical example is christmas lights - old style ones had all the bulbs hooked up in series, meaning that if one single bulb burned out the whole string would shut off because it is breaking the circuit. You had to go along and find the burnt out one and replace it - a huge pain! Modern lights are hooked up in parallel - each bulb is essentially creating its own circuit with the power source. When one bulb goes out, the rest will stay lit and it's much easier to find and replace burnt out bulbs.
In the above photos, the batteries are hooked up in series in one photo and parallel in another. When they are hooked up in series, the voltage of each battery pack is added together. Each individual AA battery puts out 1.5 volts - a battery pack has two of those batteries essentially hooked end to end in series, so each battery pack puts out 3 volts. If you hook two battery packs up in series, that generates 6 volts - which is too much for the LED and the speaker, probably okay for the motor. In the above example, I have a potentiometer hooked into the circuit to limit the voltage to the LED so it doesn't burn out.
When the batteries are hooked up in parallel, the output voltage is the same - 3 volts. However, we added more battery capacity into the circuit - our LED will stay lit for twice as long if we left this circuit hooked up!
Step 8: Explain, Expand and Evaluate
There is a lot to think about and explore when it comes to circuits. Here are just a few questions to think about when facilitating this activity:
Explain and Expand:
- What is a circuit, and what does it mean for a circuit to be open or closed?
- What happens when you add more components to the circuit without adding another battery? Why?
- What is resistance in a circuit? See above image for a graphical illustration of Ohm's law as it pertains to volts, amps, and ohms.
- Why do you think a battery will overheat when short circuited?
- What things do you need to create the simplest circuit you can think of? What about a more complex circuit?
- What other electrical components would work great as a circuit block?
- How many blocks do you think you could attach together? Would you connect them in series, parallel, or a mix of the two?
- Can you create a circuit of your own and draw a circuit diagram so that someone else could replicate it?