Day 6: We’re Rolling!

Friday, 15 September 2017

Our Braitenberg bots are coming along! After a change of course from what I wrote a few days ago — turns out the particular op amp I was using put out too little current to drive the motors — the new circuits are now tracking the light properly.

It’s subtle but can you see how that last bot turns away from the light? The student who built that one had an interesting time figuring out why his robot ran from the light. He loved learning that cross-wiring the left photo resistor with the right motor would give him the light-seeking behavior he wanted.

Today, we spent much of the period building robot chassis out of cardboard boxes because that’s what we have in abundance.

A Braitenberg vehicle built to the same specs as we use in the video requires the following parts:

  • breadboard
  • hook up wire
  • 2 NPN transistors
  • 2 diodes
  • 2 photo resistors
  • 2 geared motors with wheels (we’re using these from Solarbotics)
  • a 9 volt battery with a battery connector

We’ll build for a few more days next week at which time the students will submit a project writeup. I’ve asked them to submit video of their robot performing all its functions, schematics, and a reflection.

I’m so glad that all the student Braitenbergs are working as expected and all that’s left is to finish the chassis. The students have learned breadboarding, how photo resistors work, and how basic circuit wiring. I think that’s great progress in a week of classes. We weren’t ready to learn transistors and diodes, in my opinion. I think between those components and the missteps on starting with op amps, this project was unnecessarily complex. So, in retrospect, I might not start the year with Braitenberg, though it’s definitely a keeper.

Advertisements

Day 2: Breadboarding+

Monday, 11 September 2017

UPDATE: See the end for an easier way to build a simple Braitenberg Vehicle.

Did you know a robot can show aggression — charging forward toward light? Or fear — running away from light? Even exploration and love? The emoting robot is based on the work of Valentino Braitenberg and we’re putting some together in robotics class.

The above video is absolutely beautiful in the same fashion as Vi Hart’s math musings. The video comes out of an Instructable on building Braitenberg Vehicles. Unfortunately, the details on wiring it up were lacking:

fu6wsv9h5r9eccp-medium

Ugh, you mean I gotta refresh my memory on all this stuff?

That’s when I found breadboard diagramming software and wrote the instructions myself: Wiring a Braitenberg Vehicle. This stuff is totally untested, so I’m seriously crossing my fingers over here that it’s gonna work.

Screen Shot 2017-09-11 at 11.46.09 PM

Untested breadboard layout for a Braitenberg Vehicle.

My students have next to no electronics experience (and I have minimal — this is the first time I’ve used an op amp, for instance), so I am pleased at the step-by-step way I built it up. I’m hoping they’ll learn:

  • how the rows and columns are connected on breadboards
  • how a photoresistor changes resistance with the amount of light
  • how the Braitenberg Vehicle can demonstrate different emotions with subtly different wiring
  • how to get two wheels turning in the same direction

The Braitenberg Vehicle is a cool concept and I highly encourage you to watch the video, even if you’re not inclined toward robotics.

UPDATE 9/13:

Ugh, so sad, after hours of debugging, I’ve decided that the op amp isn’t generating enough output current to drive the motors well (maybe with different gearing I’d be good). When I shined a flashlight directly on the photoresistor, the motor let out a whine and only spun if I nudged the wheel.

So, I was thrilled when a student told me he’d found plans that use a transistor. The drawback is that we lose the functionality of speeding up or slowing down with the amount of light.

Day 1: Motors

Friday, 8 September 2017

IMG_20170908_143129

Day 1 of robotics with juniors and seniors. I handed them geared DC motors and battery packs.

“Make the motor go forwards, backwards, fast, and slow.”

I chose this activity because I’d heard my students had all levels of experience and this would be a fast way to sort them. And the kids really did run the gamut — some had a motor running within seconds and others took awhile to find the connection points on the motors.

One kid told me he and his friend want to build a golf cart driving robot that can be placed in an unmodified cart.

I’m at a new school and have a new courseload: Physics I (a conceptual physics course mostly for 9th graders) and Robotics. Come along for the school year told through pictures from 180ish school days.

Day 175: Interesting Momentum Problem

Thursday, 18 May 2017

I found this great question in an old textbook and loved it because of how it pulls together multiple topics we’ve learned:

A 300 g ball is dropped from a height of 90 cm and bounces back up to 66 cm. The change in momentum of the ball is

a. 0.18 kg m/s

b. 1.26 kg m/s

c. 2.34 kg m/s

d. 2.52 kg m/s

e. none of the above

In the lead-up to the exam next week, I gave the kids two exam review quizzes this week. Students took the quizzes in class and checked against an answer key. They then took the quizzes home and worked out the correct solutions and turned in a hopefully-perfect quiz. I graded the final result as a quiz grade.

This worked out to be a wonderful exam study tool and the above question was probably the most challenging thing on it.

Day 174: ExamGram

Wednesday, 17 May 2017

So this was interesting — I posted a series of photos on Instagram with exam review questions and egged my kids on to participate by solving the problems. Here is a sampling:

Screen Shot 2017-05-31 at 9.20.58 PM