If you cast your mind back to issue 51 of the magazine, you’ll remember a robot on the cover that you could make yourself. Its designer, Brian Corteil, has taken the lessons from making that robot to build an all-new improved version, which you can buy directly from his Coretec website.
The Tiny 4WD is the end result of this learning process, and is available as a kit that you build yourself. All you need to supply is a Raspberry Pi and a way to power it (a mobile USB battery charger will do the trick). The kit is optimised for a Pi Zero, with specific mounting points on the chassis. However, we tested it using a Raspberry Pi 3 and it worked well.
Easy build
The build is fairly quick. There are only three parts to the chassis, and one of these isn’t necessary in its basic state. The box recommends using the build in The MagPi as your instructions, but they don’t quite fit this kit. Luckily, there’s a great guide online. Online instructions aren’t ideal – it would be nice to have printed instructions in the box – but it’s enough to get you started.
We managed to get the robot up and running in just under two episodes of Brooklyn Nine-Nine, so we’d estimate 30-40 minutes’ build time, but it may take longer depending on your skills with a soldering iron. You’ll need to solder a 40-pin and a 20-pin header to the Explorer pHAT supplied with the kit, as well as soldering a GPIO header to the Pi Zero. The rest of the setup is easy: install the software on the Pi Zero (running Raspbian) and you’re ready to play!
Flexible control
From here you can use the test scripts to control the robot using a USB controller, or start making it more autonomous. The Pimoroni library for the Explorer pHAT is easy to understand – so, with the docs open and the examples to hand, you can easily start creating your own programs.
Each side of the Tiny 4WD is powered by one of the motor outputs on the pHAT. This means that, for example, both left wheels will always run at the same speed and direction as each other. This makes it easy to turn on the spot, and gives it full power when it’s moving forwards and backwards.
The Tiny 4WD is easy to customise. There are extra inputs and outputs on the board, so you can start adding additional sensors. There’s a camera mount that could be used to attach an ultrasonic sensor, or a Raspberry Pi Camera Module – like the robots in the Formula Pi racing series.
Power choices
Choosing a power supply can be tricky. The idea is to house your power source between the layers of the chassis. However, the narrow gap, partly blocked by the wires to the motors, limits the size of any power supply. You’ll also need to think about power capacity – the motors will be powered from the Pi’s GPIO pins, so your Pi will need more power than you might expect.
We do like this robot overall. The build quality is great, with a sturdy chassis made from thick acrylic, decent micro motors supplied with the kit, and the inclusion of a great motor controller in the Explorer pHAT. The soldering requirements make it unsuitable for an absolute beginner, but it’d be great as a step up for novices. It could even be used as a base by more advanced robotics users, as you can easily swap out the HAT and use a bigger Pi to add more functionality.
Unfortunately, supplies are limited for this kit, but more units are being made all the time. If you want one, you may just have to be patient. We think it’s worth the wait, though.
Last word
4/5
A great little robot kit which could do with some better build instructions. Once it’s built, however, you have a lot of options and plenty of ways to make it your own.
