IEEE Robotics & Automation Magazine - March 2017 - 79

teachers requires a huge effort, based on a good mix between
robotics and educational skills. Moreover, educational material varies from school to school, as requirements are very
dependent on local educational programs and languages. A
crowd-sourcing approach may solve this problem; an active
community of users can contribute to the development of the
material in a distributed manner, adapting the material to the
local situation. LEGO itself is moving in this direction by promoting communities of users [12] with a user-producer
interaction similar to that of open hardware projects. An
open-source community regrouping developers, manufacturers, and end users is therefore a very interesting model to
address the distributed development and sharing of educational material and the diffusion of training sessions. In this
article, we study a case of implementation of this model.
Design Choices
We designed the Thymio robot along seven main axes: a low
price to address a larger number of users; a feature set that suits
both genders and multiple ages from young children to adults;
a mechanical design that promotes creativity; a combination of
sensors, actuators, and programming features that facilitates
learning; a set of ready-to-use programs to quickly access
robotic behaviors; an accessible programming environment;
and an open-source community contributing to design and dissemination. The result is a miniature differential-wheeled robot
suited for use on a desktop [Figure 1(a)]. The robot is robust
enough to be mishandled by children; it can fall from a table
without breaking. It features a translucent white hull and a wide

range of sensors and actuators [Figure 1(b)]. The robot has an
embedded battery, rechargeable by a universal serial bus (USB),
that provides 3-5 h of power. More details on the robot and the
previous research results can be found in [13], [14].
A Low Price
Price is key in the adoption of robots by schools [15]. Thus, the
design of Thymio targeted low production costs while including a broad range of functionalities enabling flexibility. Because
in this type of robot the main cost comes from electronics and
sensors [16], we focused on low-cost sensors that allow rich
interactions with both the environment and the user.
The resulting Thymio robot possesses a large number of
simple sensors: seven horizontal proximity sensors, two infrared sensors pointing to the ground, a three-axis accelerometer,
a thermistor, and a microphone. Five capacitive touch buttons
organized as a direction pad form an intuitive user interface.
Compared to physical buttons, these simplify the plastic hull of
the robot and make it more robust. A remote control receiver
provides additional distant buttons. Most of these devices cost
less than US$0.20, the most expensive being the accelerometer
with a cost of about US$0.80, which is an acceptable price
given the possibilities it brings to the robot. We also chose lowcost toy motors and control them in speed (maximum of
13 cm/s) measuring the back-electromotive force.
We evaluated several microcontrollers and chose the
PIC24F from Microchip because it integrates a USB interface
and can drive capacitive touch buttons directly, saving additional components. This microcontroller controls all sensors

Five Capacitive Touch
Buttons, Activity Display,
and On-Off Function

USB Dongle*

Pencil Support
Li-Po Battery Level

USB Connection
Programming and
Recharging

Wireless Module*
Wir

Memory-Card Slot
Loudspeaker

Hook for Trailer
Two Proximity Sensors

Microphone
Infrared
RemoteIInf
nr
Control Receiver
Co
(a)

Mechanical Attachment

Three-Axis
Accelerometer
Thr
Thre
Thr
h ee-Axis A

Two Wheels and
Speed Control

Five
Fi Proximity
P i it Sensors for
Obstacle Detection
Two Ground Sensors for
Line Following
39 LED
Visualize Sensors
and Interactions

Temperature Sensor
Reset Button
(b)

* Available Only with Wireless Thymio

Figure 1. The Thymio robot and its main components for the wireless- and the USB-connected versions: (a) a rendering of the Thymio
robot (courtesy of Ecole Cantonale d'Art de Lausanne) and (b) a list of key features of the robot. Li-Po: lithium polymer.

March 2017

IEEE ROBOTICS & AUTOMATION MAGAZINE

Table of Contents for the Digital Edition of IEEE Robotics & Automation Magazine - March 2017