On Saturday, December 8th, 2012, we met for another in our series Educators’ Workshops, hosted by the MENTOR Makerspace at Lighthouse Community Charter School in Oakland. Our goal was to introduce basic electronics and electricity and to try out some beginning Arduino projects. The 23 attendees got to sit in the students’ seats and take the time to learn by doing in a community of supportive and enthusiastic fellow teachers in the MENTOR Makerspace program.
We began with a brief introduction by Andreas Kaiser of Pittsburg High School. Then we had a half hour or so of exploration with simple circuits using the Squishy Circuits. Aaron Vanderwerff, who hosted the event at the school long with his colleague Ed Crandall, Then led the group in a discussion about the principles that the teachers discovered empirically. Maggie liked using the project from Instructables to create the persistence-of-vision toy, especially “making mistakes but having help to figure out why.” Nathan also “found the interaction with other educators very useful. Also, having people with a lot of expertise that you can incessantly bother with questions was an invaluable tool.” Andreas appreciated “learning new ways to teach concepts and seeing what other teachers are doing in their classes.”
To provide a metaphor for understanding basic circuits, Joel Rosenberg, our colleague and the Chief Epistemologist at Otherlab, shared one from CASTLE, a curriculum developed with Melvin S. Steinberg, a professor of physics at Smith College. Joel prefers CASTLE’s “hula hoop” model over the much more commonly used water metaphor. The Hula Hoop model is described on page 29 of an article by Camille Wainwright on misconceptions :
With 4 or 5 students in a circle, ask them to hold their right hand in a loose ring around a hula hoop. Tell them to lift their left hands high (bulb ‘on’) if they feel the hula hoop moving through their right hand. The teacher is ‘in charge’ and begins to push/pull the hula hoop around in the circle. As soon as it starts in motion, all hands go up; as soon as it stops, all hands go down. (The teacher can also reverse the direction of the hula hoop, and the same results are observed.)
Wainwright goes on to describe an advantages of the hula hoop model:
It suggests that something (charge) is already in the circuit, and that the teacher/battery simply puts it in motion. When the charge begins to move in the circuit, it moves everywhere at once and all bulbs come on at the same time. The fact that the teacher can reverse the direction of charge flow is analogous to reversing the terminals of a battery in a circuit; it also suggests that bulbs are non-directional – they function equally well with charge moving through them in either direction.
An important misconception – one held by nearly all students – is that the battery is the sole source of charge in a circuit, squirting it out much like a whipped-cream can. (The term ‘rechargeable’ battery perpetuates that myth, suggesting that the battery becomes empty of charge and therefore must be recharged.) The hula hoop model helps students recognize the possibility that the charge could already exist everywhere in the circuit in which case the battery’s task is not to provide charge but to provide the energy necessary to make it move. You can ask them to consider how you would feel if you had to rotate the hula hoop for hours and hours. They’ll suggest that you’d become very tired, low on energy, and would need to eat to build up your energy, or become ‘re-charged’. (A better name for a ‘rechargeable battery’ would be a ‘re-energizeable battery’.)
Joel explained that the hula hoop model avoids common misconceptions, and it helps students visualize different concepts about circuits:
- Voltage: the teacher represents the battery, and the voltage is the push/pull “oomph” by teacher on the hoop.
- Resistance: a student’s hand on the hoop provides resistance to the spinning hoop; the student represents a bulb, and bulbs introduce resistance into a circuit.
- Current: the “charge flow rate” is the hoop flow rate. The hoop represents the charge, and exists before there is any spinning.
- Power: for the “energy flow rate”, the teacher does actually transfer “energy” through the hoop instantaneously.
Joel suggests looking at Wainwright’s Appendix B (pages 26-29) if you’d like a good summary of ideas in CASTLE. The whole paper is an evaluation of “Engineering the Future“, and includes a concise list of common misconceptions in electricity education.
Joel offered a second metaphor for thinking about the difference between circuits that are parallel or in series, and how that design choice affects resistance with the air and straw model by asking our class:
- Try blowing through a straw. Now attach another straw to its end and try to blow again. is it easier or harder to blow? It’s harder, right? This is a series.
- Now try blowing through straws that are next to each other. It’s easier than blowing through just one straw, right?
Joel later shared his cardboard circuits (which he’ll share on the blog later when they’re more developed) and a demo of a program for an Arduino Uno (or Leonardo). It collect 0-5V input data from sensors — such as the photoresistor used in the light theremin — and send it to a computer. It’s also a program for Processing, and a graphing library called gwoptics, to display the data sent by the Arduino using rotary voltmeters, a rolling-time graph (oscilloscope-like), and bar graphs. This is not well documented yet, but if you want to try using it:
- Open the attached zip file “VoltRoller-ArduinoProcessing.zip”
- Install Processing if you haven’t yet.
- Copy the “Analog0and1_5vRef_a” folder into your Documents>Arduino folder.
- Copy the “VoltageRoller_2input” into your Documents>Processing folder.
- Download the gwoptics library: gwoptics.org/processing/gwoptics_p5lib/
- Unzip the gwoptics library.
- Copy the gwoptics library into your Documents>Processing>Libraries folder.
One of our teachers with having some problems getting his Arduino set up to communicate with his computer. The troubleshooting tips in our book did not sufficiently resolve his issue, that we did figure it out in the end. These are the methods that we used to debug the problem:
- Traded Arduinos with a neighbor.
- Restarted the computer.
- Reinstalled the Arduino software.
- Found the same model of computer as his own, and checked the settings. Here we discovered that he needed to choose another port.
This exercise sparked a conversation among some of the educators in the room who had more experience with Arduino in their classrooms. A very large percentage of time is spent on troubleshooting computers and dealing with new viruses that infect computers in their labs and makerspaces. on top of this, school Internet policies are often very strict, requiring approvals and visits from the overworked IT managers at the school. teachers end up spending a lot of time installing and reinstalling software, not because of anything they did wrong, but because of the technical and logistical limitations that they face. In our work with MENTOR Makerspace, we hope we might be able to identify a dream list of what perfect hardware and software for classroom would look like. Ideally, it wouldn’t occupy any more of teachers’ precious time!
Look for our next Educators’ Workshop in February.