Hackers – Remote Controls for Our Bots!


In the Hackers group this week, we took a large step forward in our Project SABRE (Small Autonomous Battling Robotic Entities), when we started working with remote controllers for our robots.


From what the group has read, it looks like the most widely-used controllers are Spektrum-compatible DSMX or DSM2 ones. Therefore, we bought 3x Lemon RX DSMX/DSM2 receivers and one MLP4DSM Blade transmitter (as shown in the photo).

Connecting to the Arduino

Pins on the receiver are simply connected to digital pins on the Arduino.

To program the Arduino to read the receiver, this code has been cross-referenced from other forums: https://www.sparkfun.com/tutorials/348

According to the comments, while this works, you should use interrupt-driven code.

This StackExchange post has a good list of possible references:


There was a lot of excitement when people were able move the joystick on the transmitter and have it change the value being printed out in the Arduino console!

Hackers – Building Battling Bots for Project SABRE!


In recent weeks in the Hackers group, we have been refining our plans for Project SABRE (Small Autonomous Battling Robotic Entities).

Our mission for Project SABRE is to build “battlebots” that include some autonomous features. While there are many kits available for purchase, our two teams of hackers are designing and building their bots from scratch, identifying and sourcing all components ourselves, 3D printing bodies of their own designs, and programming everything themselves. Even the mentors are hands-off, helping mainly with project planning and purchasing, but not designing or making.

The main components required are:

  • 2 or 4 motors with wheels or tracks
  • Battery packs and chargers (salvaged from old toys)
  • An Arduino
  • A motor driver board or chip — these work just like the transistor circuit that we experimented with previously, but can control up to 4 motors and drive each one forwards or backwards: https://coderdojoathenry.org/2017/11/22/hackers-a-joule-thief-and-controlling-motors/
  • A servo motor if needed for a flipper arm
  • A 2.4 GHz radio transmitter and receiver

Stay tuned as the work continues in the coming weeks!


Hackers – a Joule Thief and Controlling Motors


In the Hackers group, people worked on two different projects, making a Joule Thief and controlling motors.

Joule Thief

A Joule Thief is a small circuit that can boost the voltage from a small power source. Typically, it is used to power a 3-volt LED from a 1.5 volt battery. Because of how it works, it can continue to light the LED even when the battery would usually be considered to be “out of power”, when its voltage drops below 1v.

Here is a Wikipedia article. https://en.wikipedia.org/wiki/Joule_thief

people in the group found various tutorials online, such as this one from Make Magazine: https://makezine.com/projects/joule-thief-battery-charger/

Motor Control with an Arduino

Continuing our work on Project SABRE, we were figuring out how to control motors.

A simple way to control the speed of a motor is to regulate its input voltage. In Arduino code, you set the output voltage of pins. However, you CANNOT just hook them up to the motor, as it will draw too much current and damage the Arduino.

The solution is to use a transistor: power from a 9V battery or the 5V USB power supply from an Arduino powers the motor with current flowing through the transistor, and we regulate the current flow by applying an appropriate voltage to the middle leg of the transistor.

Two more components are needed: a resistor for the middle leg of the transistor, and a diode to get rid of any voltage spikes that come from the motor acting as a generator if it us spun by hand, or when it is spinning down after current to it is cut.

More details here: https://learn.adafruit.com/adafruit-arduino-lesson-13-dc-motors/arduino-code

We also looked into stepper motors, and controlling speed by reading a value from a potentiometer, instead of just typing in a speed: https://www.arduino.cc/en/Tutorial/StepperSpeedControl


Hackers – Project SABRE


In the Hackers group, we started working on design of semi-autonomous or fully-autonomous battle-bots.

We are using the name “Project SABRE” as described in the graphic above.

Members of the group took first steps in learning how to control a robot by setting up a controllable circuit for LEDs.

This should be an interesting project to return to after the break!



Hackers – More 3D Modelling


This week in the Hackers group, rather than demonstrating how to use SketchUo, we showed some models that Kevin/Michael had built (see above), and the challenge was to recreate them. Some people got so far as to be able to print their models.

We also started some planning on an overall theme – more on that next time.

Hackers – 3D Modelling with SketchUp


At this week’s session, Kevin introduced everybody to SketchUp, a free 3D modelling program. Models built with SketchUp can be exported to a format suitable for input into Repetier Host, to prepare them for 3D printing.

Incidentally, other options for 3D modelling include Blender (which some may have used previously for modelling) and TinkerCAD (which is web-based so does not require installation).

Here are some notes on getting started with SketchUp – they are taken from an NUI Galway summer camp I was involved in organising a couple of years ago: sketchupnotes

By the way, the picture above is a SketchUp model I built previously of a room.

Important: to export SketchUp models to Repetier, you first need to install the SketchUp STL Extension. Instructions:

  • n the SketchUp main menu, select Window – Extension Warehouse.
  • Search for SketchUp STL (see below), then go through the steps of downloading and installing.
  • Note that you may need to create a Trimble account (Trimble is the company that develops SketchUp).
  • You may see a warning that it is not marked as compatible with your version of SketchUp, but just press OK.
  • After installing the SketchUp STL extension, you will have a new menu item: File – Export STL.


Hackers – Getting started with 3D printers


At the Hackers group, we started learning how to use 3D printers this week. 3D printers are a fantastic technology for turning 3D computer models into physical objects. They are also impressively inexpensive. For example, one of the printers we are using, the Arduino-based Materia 101 printer, costs about €600.

Thanks to Kevin’s employer, Boston Scientific, who have loaned two 3D printers to us and are also covering the cost of the plastic “ink” used in them.

Here are Kevin’s notes on how to set up a 3D printer: 3d-printer-setup (PDF)

Here are the configuration files needed for the Materia 101: https://www.dropbox.com/s/6otj5ok7i00ikds/Slic3r-Materia101-Settings.zip?dl=0

We have another model of 3D printer, the Prusa i3 MK2 in the group as well. We will post notes about using it at a later date.

And here also is a diagram Kevin prepared, showing the 3D printing workflow:


At our next session, we will look at how to do some 3D modelling to create objects we can print. Should be fun!

Congratulations to all our ninjas who received belts in Summer 2017!

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On 27 May 2017, at our final CoderDojo Athenry session of the 2016-17 year, we awarded a total of 93 belts to our ninjas for their great individual achievements in acquiring and demonstrating coding and computing skills. And then we had a party with pizza!

Here is a link to our presentation from the day: CoderDojo Athenry Belts Day 2017

We are very grateful to Clarin College Athenry and the principal, Ciaran Folan, for their enabling CoderDojo Athenry by making the school and its wifi available to us.

We are also very grateful for the sponsorship and support we have received this year:

  • Galway Roscommon Education and Training Board, who provide us with an annual Youth Club Grant
  • Medtronic, employer of our mentor Declan Fox, who provide us with a grant to match Declan’s excellent volunteering
  • HP Enterprise, employer of our mentor Mark Davis, who provide loaner laptops that we make great use of
  • Boston Scientific, employer of our mentor Kevin Madden, who provided us with a set of 3D printers this year, which allowed a great new learning experience

Because of these supports, no child or parent/guardian ever has to pay to participate in CoderDojo Athenry.

This year also, mentor Martha Fahy introduced a new idea, “Java Dojo”, where parents can buy a cup of tea/coffee, providing additional funds. With these, we have been able to buy a speaker system, electronics needed by some of our groups, and our own 3D printer! Thank you, our CoderDojo ninja sidekicks!

And of course we must thank our mentors, who volunteer their time and expertise entirely without charge week after week, to make CoderDojo Athenry the success that it is.

Here is the full list of belts we awarded:

  • Explorers:    44     (39 Yellow & 5 White)
  • Advancers:  18
  • Bodgers:     17
  • Hackers:      8
  • Creators:     5
  • Black Belt:   1

Special mention must go to Eoin Clarke, who received our first ever black belt award. Eoin has been in CoderDojo Athenry for several years, working his way up through the groups, and this year took on the role of Mentor. Well done, Eoin!

Above are some photos of the belts awarded. You can find more on our Facebook page: https://www.facebook.com/CoderDojoAthenry/posts/1465673366786859

CoderDojo Athenry is now closed for the summer. See you all in September!