Sandwich-bot

February, 2012 – April, 2012

The principal to my kid’s elementary school asked me to start a Robotics club in order to take advantage of some funding provided by a local business.  Having several robot builds under my belt, I was excited to get involved, give back to the community and spend some quality time with my kids.  My wife is on the PTO board and gave me lots of guidance and help on running the after-school program.

As I started the planning process, it was clear that a popular robot kit like a Lego Mindstorm NXT 2.0 was far too expensive and would mean no one would sign up.  I really wanted everyone to have a robot, and be able to take it home with them at the end of the class.  So, I went to work designing an inexpensive robot.  I took ideas from the Society of Robot’s $50 robot and Robot Room’s Sandwitch robot.  What I came up with was an inexpensive robot (about $50) that could be built from scratch by each student.  I originally opened the class for 10 students (5th and 6th graders), but there was such overwhelming demand, I added another 5 more slots for a total of 15.

The robot has 3 wheels (2 run by geared motors and a 3rd omni wheel) with differential steering.  It has 2 “eyes” that were photo-resistors and 2 LEDs for sensor feedback.  It also has a simple buzzer that we later used to have the robot play music when it was first turned on (a very nice feature of the PICAXE).  The robot brain was a PICAXE 14M2 chip.  The whole thing was powered by a 9V battery.  I used a clear solderless breadboard to house the microcontroller and all the electronic components.  The robot is a photovore – it is attracted to light.  When you shine a light into the left eye, it turns left.  When you shine a light into the right eye, it turns right.  When you shine the light into both eyes, it goes straight.  I provided each kid a small LED penlight so they could drive the robot.

I built a bunch of PowerPoint decks that outlines the step-by-step process.  I ran the class for 2 hours, every other Monday over a 14 week period.  I bought a Geek Labcoat from Sparkfun and wore to to class.  I peppered the PowerPoint decks with jokes and really had fun with it.  We had a great group of kids and I was pleasantly surprised to see a good mix of boys and girls.

I built the curriculum to focus on 3 main areas:  Mechanical, Electronics, and Software.  We started with the mechanical and we assembled the motors, wheels, and the body. Next, we discussed the electronics.  I introduced the class to the concepts of resistors, capacitors, transistors, diodes, and a variety of other components used by the robot.  We spent 2 meetings assembling the components.  The kids especially liked using the wire cutter/stripper to wire up the components.  Next, we focused on the software.  I had the kids help me write the pseduocode for the logic, and then had them type in the robot logic into the BASIC IDE provided by the PICAXE.  Finally, we I let them loose in the art room where they decorated each of their robots to create some very unique and clever designs.

The program was a huge success.  A highlight of the program was when my class got invited to the school Science Fair where we were allowed to show off our robots to the school.  There were other great moments when the kids were clearly having ‘ah-ha’ moments as we were building the robot.  I’m definitely looking forward to running another program next year.

Pictures:

423181_382840398409857_1361660973_n  The sandwich-bot (assembled, but un-decorated)

396317_382840455076518_296603365_n  A close up of the breadboard with the components assembled.

394024_382841241743106_2089835434_n  I assembled the parts into 15 kits so each kid could build and keep their own robot.

Parts List

SandwitchBot Parts

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