Because our secondary school doesn’t have a Robot Club my Mum (Miriam) and I (James (14)) found out about Leicester Hackspace (http://leicesterhackspace.org.uk/) and went along with my sister (Mary (12)) to see if they could give me some useful advice about robot building.
We became Members of Leicester Hackspace in January 2018 and my Mum and I started to attend regularly because there are lots of really supportive people with lots of experience to help. Plus lots of different resources (i.e. 3D printers, soldering station, electronic equipment to hack and borrow, etc.)
Steve has been the main helper at Leicester Hackspace. Lots of other people at Leicester Hackspace have also offered help and encouragement including: Divya, Bill, Matt, David and John.
We decided to name the robot ‘Ratae Robot’ because of all the help from Leicester Hackspace and because in Roman times, the town of Leicester was called Ratae Corieltauvorum or Ratae for short.
Steve told me (James) about Raspberry Fields and suggested we go on 30 June 2018.
At Raspberry Fields my Mum and I spoke to the organisers of Pi Wars at Raspberry Fields and I experienced one of the Pi Wars challenges. We also looked at and talked to people on the different stalls selling different robot components and with advice from them and Steve purchased some components.
We submitted an application for Pi Wars in September 2018 and were placed on the reserve list. We decided to carry on working on the robot and to keep the organisers up to date with our progress.
When we were invited to Cambridge Makespace Robot Club (http://makespace.org/) on 12 January 2019 I decided to go along with Ratae Robot and my Mum because the Pi Wars organisers were there, along with other people who were entering Pi Wars. Brian C and Brian S both gave lots of help and advice and we found out more about the competition.
We were given a Pi Wars place in February 2019.
2. Researching how to build a robot and what components to use
I looked at the requirements of Pi Wars and thought about possible approaches to build the chassis (see Table 1).
I then prototyped with a simple LEGO and Meccano chassis, to get it moving and to try out different codes with lots of help from Steve.
Table 1: Chassis Material and Design Options
| Possible |
|Meccano (see Photos)||Easy to adapt |
|Heavy, after |
awhile can fall
apart when the
|Yes||Can keep |
screws to keep it together.
|Coretec ‘Tiny |
|All of the robot |
design is done
for you and all
the code for it is
| No flexibility |
|No||I like the |
designing part of the process
|Laser cut |
|Accurate, fast||Design |
got to screw or
hard to adapt
|No||Can’t be very |
|3D printed||Can get almost |
any shape you
designs available from
|Slow, can deform when printing, |
hard to adapt
| Yes, for |
plastic – see
|Very time |
(see Photos 1 and 2)
|Easy to change design||Falls apart and not very robust||Initially||I started with |
this, but it kept
Photo 1: Earlier LEGO and Meccano prototype – too top heavy
Photo 2: Another prototype, as you can see the wheels are off centre, the power wire is too long, and the majority of the weight is outside the wheelbase.
Table 2: Other Material Resources Used
| Raspberry pi zero w |
(pre-soldered 40-pin GPIO)
|A really small computer – with mini-HDMI, micro-B OTG USB, and 40-pin GPIO|
|Explorer phat||To control the components|
|Pimoroni moon buggy wheels x4||Grippy wheels so the robot can move|
|Micro metal gear motors 50:1 and shim, plus bracket and washer||To move the wheels|
|NOOBS 16GB microSD card||To store the code used by the Raspberry Pi|
| 2000mAh – LiPo Battery Pack |
Adafruit Lithium battery charger
| To supply power to the robot |
|LiPo SHIM|| To connect the Lithium battery to the |
|Raspberry Pi Compatible Wireless Gamepad / Controller with dongle and 3AAA 800 mAh rechargeable batteries and charger|| Controls the robot for the remote control |
| Breadboards and Male to Female and Male |
to Male – Jumper strips
|To wire the components together|
|Ultrasonic sensor|| Reads the distance to obstacles – for |
|Line follower|| Allows the robot to follow a line on the |
ground – for autonomous challenges
| Various cables with appropriate connectors (mini HDMI to HDMI adaptor and micro-B |
| Transport power, and sometimes also data |
|Wireless Router||To connect the Raspberry Pi with the laptop|
Table 3: Critique of Different Batteries for the Raspberry Pi
| Possible |
|AA battery |
| Can get them |
has a switch
|Doesn’t come |
(would have to
Different voltage if using
|No||Couldn’t get the |
with these (The
be 4.8v with
rechargeable and 4.5v with
|Pound land |
|Very cheap, light, small||Short life, not |
very reliable, can catch fire
| Yes – initially |
(see Photo 1)
|Started with |
these, but found
they didn’t last
for long enough
|Power Bank |
Anker Astro 6700mAh
|Long lasting, |
lights to show
|Heavy and big|| Yes – tried these second (see |
Photo 3 under
| Used this type of battery |
because it was
recommended by Brian C a
previous winner of Pi Wars
|2000mAh – |
|Light, long |
|Can catch fire. |
Have to buy a
Need to solder a
shim onto the
|Yes – used in |
|Used this in the |
because we had
to replace James’ Pi with Steves’
James’ Pi was only
Steves’ Pi has got the
shim for this
battery soldered on so now only works for this
Photo 3: An earlier version of Ratae Robot with chassis for the Power Bank Anker Astro 6700mAh battery
We tested to check that rechargeable batteries can also be used for the robot controller, which reduces electronic waste which is especially harmful to the environment because of the chemicals and heavy metals used.
Table 4: Software resources
|Etcher||To burn images to the SD card to save what is needed for the Raspberry Pi to work|
|OpenSCAD||3D printing software|
|VNC Viewer and PuTTY||To remotely control the Raspberry Pi from a laptop for coding purposes|
|Python 3 (IDLE)|| Code to control robot often available as open source code which I modified and improved |
for the challenges with lots of help from
Steve at Leicester Hackspace
|Angry IP Scanner||To find the IP address of everything on a network to find the Raspberry Pi IP address|
Table 5: Risk assessment
|Risk||How I could resolve it|
|Short circuiting||Check circuits before plugging in the power.|
|Burns (soldering iron)|| Make sure where soldering is not messy or |
cramped, access to cold water and a first aid
kit in case of burns.
|Components getting hot|| If anything is getting too hot – fit a |
| lithium-ion and lithium-polymer batteries |
| Keep them in a metal tin whilst charging and don’t leave them unattended or on charge for |
|Burning out motors||If the robot isn’t moving, make sure nothing is stuck in the gear box.|
Table 6: Problems identified and how I overcame them
|2 LEGO wheels and caster used to start with – slow moving and not very stable||Replacing with 4 grippy wheels (see Table 2)|
|Chassis too long||Re-designing and test driving|
|Robot top heavy||Re-designing and test driving|
|Breadboard only stuck on with double-sided sticking tape so loose|| Use thick elastic band to hold in place |
(see Photo 4)
|Bolt head of the motor mounts too small to be compatible with Meccano||Reusing a plastic lid to make washers|
|Wi-Fi crashing|| Using a spare router from Leicester |
Hackspace to create a separate network for the Raspberry Pi and laptop.
|Insufficient battery life for the Raspberry Pi||Changing the batteries used (see Table 3)|
| Problems charging the AAA rechargeable |
batteries for the controller
|Using a better battery charger (on loan from |
Divya) which charges each individual battery
and has an indicator to show when each
battery is charged.
| Problems with Raspberry Pi working |
| Replacing with a different Raspberry Pi and |
3. Finalising Ratae Robot
Photo 4: Final Robot with Attachment for Pi Noon and Spirit of Curiosity Remote Control Challenges
Photo 5: Attachment for Space Invaders Remote Control Challenge
Photo 6: Attachment for Line Following Autonomous Challenge – still working on this!
4. Test Driving
As well as my sister and I test driving each version of Ratae Robot at home and at Leicester Hackspace. I also went to the Cambridge Makespace Robot Club on 12 January and 9 February 2019 to test drive Ratae Robot with my Mum. Steve came with us in February.
My sister and I really enjoyed Leicester Hackspace Raspberry Pi Birthday Party on 2 March 2019 where the Pi Noon challenge was replicated and guests drove Ratae Robot in competition with another robot. Ratae Robot performed well as it was very quick and more manoeuvrable than the other robot.
5. Useful tip
LEGO Technic, Meccano and Breadboards are compatible and can be attached together for robot prototyping and building
6. How I would change the project if I did it again
Spend more time thinking about how to make a lighter, more robust chassis.
Have better weight distribution.
Use strip board and solder instead of bread board because this would give a better connection and would be less likely to come loose.
Try out different turning methods, such as Ackermann steering geometry and/or omni-directional steering.
Develop the autonomy further.
7. Thank yous
Leicester Hackspace and Cambridge Makespace are really supportive and inspiring, Ratae Robot would not have been built without them. They have taught me lots and really helped me. I really enjoy the collaborative atmosphere and I will keep going regularly to Leicester Hackspace to work on other projects. Leicester Hackspace members also really helped me find lots of open source code and information that helped me with my research of the components and coding I needed. Thank you!
Table 7: Information Sources
|The Unofficial LEGO Technic Builder’s Guide (book)|| By Pawel “Sariel” Kmiec, 2017, No Starch |
Press, San Francisco
|Robot Wars – Build Your Own Robot (book)|| By James and Grant Cooper, 2017, Haynes, |
|Know Your Tractor (book)|| The Shell Petroleum Company Limited, |
|Pi Wars 2019 website|| https://piwars.org/2019-competition/ |
Pi Wars competition information and advice
|GPIO Zero|| https://gpiozero.readthedocs.io/en/stable/ and https://pinout.xyz/ Example open |
source codes and information
|Pimoroni|| https://shop.pimoroni.com/ Shop selling |
|Pi Hut||https://thepihut.com/?gclid=EAIaIQobChMI5eDIqf304AIVyrztCh2y Yw8QEAAYASAAEgJpkPD_BwE Shop selling robot components|
|MagPi magazine|| https://www.raspberrypi.org/magpi/ |
Magazines including advice on how to build
robots for Pi Wars in Issue 68
|Git Hub (coding)||https://github.com/ApproxEng/approxeng.input/tree/master/src/docs/examples|