The Plan Part 1 - The Robot

This series of posts are about how we plan to tackle the robot build and implement the challenges. Whether the finished result will be anything like this, we'll have to wait and see. 

The Robot 

Nanny McPi will be a straightforward 4WD skid steer robot. It will be built out of 3mm plywood with hex spacers in between. When building Sputnik for the 2019 competition I received a Dremel Moto-saw for my Birthday. This is a portable scroll saw that meant I could cut the plywood fairly accurately without the need for a laser cutter. 

I'm using the same technique this year. I design the 2D plywood layers in inkscape. I then print this out and stick the printout to a sheet of plywood using a removable spray adhesive. Then I can cut out the shapes with the scroll saw and drill all the holes for the hex spacers and any other mounts using a cordless drill.

We're planning to use these 12V motors: https://www.technobotsonline.com/918d100112-1-re-280-1-4mm-metal-geared-motor-100-1.html 

They're almost half the price of the Polulo ones we used on Sputnik, so hopefully they'll be OK. 

We're planning to swap the wheels out between the automated challenges and the obstacle course, since all the automated challenges will be on a smooth surface, and we're likely to take the robot outside for the obstacle course, so will need something a bit more 'off road'

Controlling the robot will be a Raspberry Pi 4 with a Red Robotics Redboard+ motor controller hat on top.

In Nanny's nose, we'll have our sensors - a Pi Camera and a HC-SR04 sonar sensor. The only bit of custom electronics I'm attempting is a simple potential divider to take the HC-SR04 output down from 5v to 3v to avoid any magic smoke. In Sputnik we had a lot of joy with 5 of these sonar sensors. We used them in all the challenges to detect distance. However we had a separate arduino handling the sensors. It's usually not recommended to attach them directly to a Pi, since they need accurate timing. However, I've done a prototype using pigpiod, which claims to provide accurate timing information and have had promising results. 

For decoration and fun, we're also planning to add some movable eyes on the front, with a wig and hat on top. However this will be the last thing to do as we want to concentrate on the challenges first. 

And that's really it for the main robot.