Cheap Robotics

by Les Pounder

Yeah the GIF is @all_about_code robot made from the Cam Jam Kit 3 and an old cover for a power socket.

For some Friday fun this week...

It's spreadsheets!!!

Before this blog post is hurriedly closed, give me a moment.

The other day Laurence Molloy gave me a challenge .

Can cheap robotics kits be made by a school?



It ain't pretty but this is my spare parts robot, built from my first Raspberry Pi and a lot of Chinese eBay components.

Robotics is a deeply personal project. You pour your heart and soul into building what you consider to be the perfect robot. Sure you may not agree with some of my choices, but that is the beautiful thing about Maker Culture, everyone sees things differently and we all make something different!

Goals for this post

Create three options

  • A kit from UK sellers.
  • A kit from China to illustrate how cheap it can be.
  • A pre-selected kit from UK sellers.

All options must support using with a Raspberry Pi and a micro:bit oh and be cheap!

Let's go shopping.

For every option I standardised the kit, to make it easy to compare. The only exception is my "off the shelf" kit list, but you'll see why later.

What's on the list?

L9110S

We start this kit by introducing the L9110S motor controller. Not as well known as the L293D etc but a cheap and competent motor controller.

Motors 6V Geared Motors

These bright yellow motors are very common in basic robotics. They are quick, easy to build into a kit, and very easy to work with.

Wheels

A robot without wheels...well that could be a biped, quadruped, hexapod etc. But wheels are the easiest way to go.

Chassis

You can buy a chassis, but where is the fun in that? Build your own chassis from whatever parts you can find. I once built a robot using a USB battery pack, robot bits and lots of hot glue!

Battery Box

Your motors will require external power as the GPIO of the Raspberry Pi and micro:bit is too weak to supply the current necessary to start the motors. AA batteries are plentiful, but for a better solution you can use a USB battery...Poundland sell them. You just need to strip an old USB lead and solder some connections to power and ground, then use that to power the robot.

Obstacle Sensor



An expensive purchase, and some would say

"Les why are you recommending an infrared sensor rather than a good ol' HC-SR04 ultrasonic sensor?"

Well the IR obstacle sensors offer enough input to give your robot the information that it needs to avoid crashing into walls. The best part is that these sensors do not require any special wiring, or voltage dividers, so you can get started quickly.

micro:bit Specific board



This robot uses a similar chassis to the Raspberry Pi one above, but this time I used Kitronik's motor driver board.

I wanted to reuse the same components across the Raspberry Pi and micro:bit. Sure I can purchase Kitronik's wonderful Motor Driver Board, but that only works with the micro:bit.



Image copyright Kitronik

So I suggest this micro:bit to male header pin breakout board. It's cheap, can be used with breadboards and enables us to reuse the components from the kit above.

UK Sellers

The bill came to £24.86, and that does not include postage!

China Sellers

The bill came to £13.95. Roughly £10 cheaper than the UK. Postage is also inlcuded.

Off the shelf kit Cam Jam Kit

This came to £25.49 (postage not included), but most of the components, except for the micro:bit specific board and the L9110S, are in the Cam Jam Kit 3 box.

Conclusions

Buy from China

If you need it cheap and don't mind waiting 4 weeks...and your school can use eBay. But customer service, possibility of items being lost in the post or the wrong item delivered are very high. So buyer beware.

Buy from the UK

If you need it quickly, you need a proper VAT receipt and want after sales support / customer service.

Buy the off shelf kit

If you want someone to pre-select the bits that you will need. But note that for the Cam Jam Kit 3 we had to purchase an L9110S motor controller, even though the kit comes with a DRV8833 based controller. The DRV8833 is made for the Pi, and yes we could hack something to use it, but it wouldn't be a simple task.

Here is the spreadsheet

If you really like spreadsheets, here is my complete Google Doc for you to refer to.