A few people on Twitter asked for a BOM for my CodeClub sub-£15 robot kit. So here it is:
L9110S DC motor driver board - £1.72
Power bank - £2.67
HC-SR04 ultrasonic distance sensor - £0.99
I already have enough Pis, cases, breadboards and leads but for completeness if you were starting from nothing:
mini breadboard - 5 for £2.09
M-F jumper leads - £0.89
F-F jumper leads - £1.05
For the Pi itself, any model will do. I'm planning on using our original model Bs but if you were buying just for this project I'd go for model A+s or o Pi Zero.
In many cases you can get the components even cheaper (per unit) if you're buying larger quantities.
The only other thing you'll need is AA cells to power the motors and (optionally) a wifi dongle if you want to remotely control the robot.
In oder to fit everything onto the chassis shown above I had to drill some extra holes, mainly to accommodate the Pi in its PiBow case and allow the power bank to be slung underneath. Although this worked fine, I wanted to make things simpler so I've been developing a 3D-printed chassis that has slots for the main elements and also allows the Pi (the heaviest part) to sit more towards the centre.