Alive - Lego Robot on the Run

The most important message at the very beginning: This project is very alive - even without me finding time to blog...

My son is really happy programming his Arduino (in fact an Arduinio clone: ITeaduino BT as described in my blog from October 2013) with S4A.

At the very beginning, he worked through the excellent documentation Elisava Workshop Materials 2011 provided from Citilab. This gave him the knowledge and the confidence to start setting up his "ArduBot" entirely built from the LEGO Technic set 9390 and some special parts, I've already described.

ArduBot - from the side

A permanent bluetooth connection allows "remote controlling" of the robot's actuators and sensors with S4A. This really works fine - and I really dont understand, why this way of connecting to an Arduino is not much more widespread.
Modified microservos to act as continuous rotation servos move ArduBot, IR sensors prevent it from collisions, whereas an ultrasonic sensor (like the famous PING!) provide a long distance detection of obstacles (not mounted on the picture above) and small IR sensors allow the implementation of a "line follower".

ArduBot - from front angle

What we learnt from the modification of our microservos is a different story, enough to fill another blog as well as construction details of our new tech toy...

Getting things started

Enough of grey theory! As the birthday of my son drew nearer, it was due time to get a move on. So I ordered necessary parts to implement an Arduino controlled LEGO Technic /  Education robot programmed with S4A for the sake of easy installation combined with a workshop materials well thought through.

Here's my shopping list for anyone who wants to tackle a similar project:

1. First the heart of the robot: I ordered the ITeaduino BT to take advantage of directly attaching analogue and ditigal sensors to the electronic brick compatible connectors as well as to connect wirelessly to the Arduino clone via Blueetooth
2. A small size breadboard and an Arduino + breadboard holder for desktop experimenting, an additional mini breadboard to mount directly to the robot, jumper wires, a battery case + rechargable NiMH batteries (6xAA) to provide power for a wireless robot and some electronic parts for first steps into "physical" computing
• 3 red LEDs, 3 yellow LEDs and 3 green ones
• 1 RGB LED
• 10 resistors 220 Ohm
• 5 resistors 10 kOhm
• 1 potentiometer 4,7 kOhm lin.
• 1 LDR (light dependent resistor) 5 kOhm (@1000 lx)
• 3 push buttons
• 1 shift register (SIPO) 74HC595
3. To provide "real world" feedback I decided to order different distance sensors:
• A double pack of Polulu QTR-L-1A reflectance sensors e.g. for edge detection or line following
• Two Microbot digital distance sensors with Sharp GP2Y0D810Z0F
• One Seeedstudio ultra sonic range measurement module
4. As mechanical components a LEGO Eduction set 9632 and a LEGO Technic set 9390 are already available plus some other LEGO Technic parts of unknown provenience.To provide a "case" for the Arduino, an integration of servo motors as previously described and gears, I ordered some additional parts directly from LEGO
• 4 Flat Panels - LEGO part no. 4621555
  
• 4 Beam R. Frame 5X11 Ø4.85 - LEGO part no. 4540797
• 4 Beam Frame 5X7 Ø 4.85 - LEGO part no. 4539880
• 4 Gear Wheel T=24 - LEGO part no. 4211565
• 4 Double Conical Wheel Z36 - LEGO part no. 4255563
• 20 Connector Peg w. Friction - LEGO part no. 4121715


5. Originally I thaught a standard servo would fit for integration into the LEGO rectangular frame (#4540797), but as the servo's axis has to fit into LEGO's grid dimension, I couldn't find a standard servo fulfilling this boundary condition. So I decided to go for mini servo fitted with an insert into this frame. To provide continuous rotation this type of servo motor has to be "hacked" as described several times on the internet; any particularities hacking this specimen I will describe in a later posting.

• 2 Modelcraft / Top-Line mini servo RS-3 

All in all, this list adds up to about 130 EUR - including delivery costs.

The Robotics Platform

The mechanical setup of an Arduino controlled roboter can be done in uncountable ways. In the following I will describe some approaches I investigated in more detail.

• Based on the well known BOE-Bot, the PARALLAX Robotics Shield Kit presents a kind of "turnkey" kit for an Arduino to move around by itself.
• Robotics can be as simple as described in WirMachenRoboter.com (the German version of Let's make robots).
• Following the path using LEGO Technic / Education as a mechanical robotics platform the use of a LEGO Technic kit (mini tow-truck - LEGO 9390) as a mechnical robotics platform is shown in Robot Arduino with several examples.

In my opinion, the only disadvantage of the latter is the very unprotected mounting of the electronics parts. But as LEGO provides the possibility of ordering single bricks, you can easily use special bricks (in this case special beams) to create a protective housing for your Arduino.
With special beam part # 4621555 I found something best described as a flat plate, 5 x 11 holes in extend, two of them can form a mounting plate 10 x 11 holes (7.9cm x 8.6cm) wide, a second set of them a cover. Part # 4540797 is a ladder shaped structure - also 5 x 11 holes (3.9cm x 8.6cm) wide - ideal to form the sides of a housing.

Browsing through LEGO's special beams I also stumbled over part # 4539880 - a rectangular shaped beam which could be used as a mounting frame to servos as its inner spacing of 3 x 5 holes (2.6cm x 4.1cm) fits in length just to standard servos.

Where it all begins

Kids are getting older and more ambitious. So, no wonder, my son after gaining some experience in programming with Scratch wants to get physical. For his upcoming birthday a programmable robot is THE number one on his whishlist.
 
To make a long story short, it all boils down to a robot which could be controlled by Scratch or any other graphical programming language with a similar concept. A potential platform would be LEGO Mindstorms NXT / EV3 which also gives the possibility to create a myriad of different robots - most exciting! But as the target groups of these sets are educational institutions they definitely exceed a birthday's budget, even with all grandparents and parents joining forces. And to my opinion they are too "ready made" - you can't see the underlying technology and thus you don't get a feeling how to realise projects in the "real world".
On the other hand, the Arduino project is quite famous and I'm impressed how well documented these microcontroller boards are, how easy they are to come by and how many slightly modified clones are around - all of them (Arduinos and clones) with a reasonable price tag. So it seems a good idea bringing Scratch and Arduino together.

This Blog will deal with the advances to create a robot controlled by an Arduino, graphically programmed and - when possible - taking on the idea to use LEGO as the mechanical robotics platform.