Credit: This project is inspired by Beetlebot by robomaniac.
Update: I've since renamed this to Pet Bot. (The video still shows it as Catfish Bot)
I teach Robotics to young makers on ESP8266, Arduino, and Raspberry PI platforms and one of the challenges I have is that kids nowadays do not understand basic electricity and they have never used a screw driver before. So, as a precursor to much more intimidating and complex Robotics projects, my curriculum now includes a series of mini projects that focus on basic knowledge in electricity and mechanical while getting used to basic tools such as a screw driver and glue gun. This Pet Bot fits that criterial; it is simple yet has "sensors" to detect and avoid obstacles without a brain (microcontroller/cpu). It meets the classic definition of a robot without introducing a microcontroller and coding!
In order to make this kid-friendly and easy to assemble, I put together a kit that requires no soldering and uses a popular 2WD chassis found on ebay, banggood, and aliexpress. (While this 2WD chassis is probably oversized for this project, my plan is to reuse the chassis for more advanced Robotics project in the future.) All electronic components are pre-soldered with Dupont connectors and a mini breadboard is used to connect wires.
Step 1: Parts & Tools
The parts you need to build your own Catfish Bot are as follows:
(Note: all electronic components have Dupont connectors since I'm using a solderless kit.)
- 2WD car chassis kit (aliexpress, banggood, ebay)
- 2 x 3 (or 4) AA battery holder & 6 AA batteries
- 2 x SPDT switch with a metal lever and roller
- 2 x M3 * 30mm screws and nuts
- 2 x wood coffee stirrers (I'm using Starbucks stirrers)
- Toggle switch (main on/off)
- Mini breadboard
- Dupont cables
- Wire ties
- Cardboard, googly eyes, spray paint (optional)
- Screw driver
- Glue gun
- Scissors/knife (optional for making your own casing)
Step 2: Hardware Assembly
Assembling the Catfish Bot's body consists of attaching following parts to the car chassis. (Photos show protective sheet still on Acrylic pieces and that's only because unpeeled pieces show up better in photos. You should peel them.)
- SPDT switches with 2 x 30mm M3 screws (See the photos for their orientations)
- Two battery holders with hot glue gun or foam tape
- Mini breadboard
- Toggle switch with hot glue gun
Use the uploaded photos as your build guide. Don't attach coffee stirrers and wheels yet. It's easier to test your wiring without them.
Step 3: Wiring
Catfish Bot uses same schematic diagram as the original Beetlebot and here is the latest article on Make: that explains the circuit. Read this article to understand how the circuit works.
Just follow my wiring diagram as shown in the diagram.
First, work on connecting the left motor and the right SPDT switch mounted on the top. Turn on the toggle switch and the left motor should turn in forward direction. Push the right SPDT switch and the left motor should turn in reverse. Make sure you test this out before connecting the other side.
Once you're done connecting all motors and switches, do the final test. If everything works, use wire ties to organize wires and use hot glue to secure Dupont connectors to the breadboard.
Step 4: Whiskers & Wheels
The coffee stirrers I got from Starbucks are slightly wider than a gap in between the roller and the plate on SPDT switches so shave about 1mm from the width on one of the ends. Insert the shaved end through the gap in between the roller and the plate. Use a wire tie and glue gun to secure the stirrer. Do this for both switches.
Lastly, attach two wheels.
Step 5: Casing (Optional)
I used a piece of cardboard to make a cover for the robot. It looks like a catfish so I decided to name it Catfish Bot. I spray paint both the casing and "whiskers" in black and attached googly eyes.