Alexandre B A Villares

Lousa mágica & Lousa paramétrica

(versão em Português)

Tools for drawing with potentiometers (take a look at the GitHub repo!)

Lousa mágica is something like “magic blackboard”, it was the name in Portuguese of the “Etch A Sketch” drawing toy that inspired this project. Then Lousa paramétrica would mean something like “parametric drawing board”.

Brief history

Magic Drawing Board video - Lousa Mágica
Lousa mágica video at Sesc 24 de maio - credits: João Adriano Freitas

tweet from Sesc 24 de maio inauguration It was also possible to post tweets with the drawing content (using a Twitter API library).

Sample of images created by participants

Setup instructions



  1. Download and install the Arduino IDE;

  2. Connect your Arduino/board to your computer, open the Arduino IDE, and in the menu File > Examples > Firmata look for the sketch called Firmata All Inputs. Next, select your board’s model in Tools > Board: , and in Tools > Port, the USB/serial port the board is connected to. Lastly, click the button to upload the sketch to the board;

    Known problems:

    • Some Arduino clones need a special USB driver: How to Install CH340 Drivers
    • If you use Linux, you might not have permission to access the USB/serial port, that can be corrected by typing sudo usermod -a -G dialout <your username> in your shell prompt.
  3. Connect each potentiometer to your Arduino/board according to the image:

    4.1 Connect the side terminals of each potentiometer to the 5V e GND pins,

    4.2 Connect the central terminals to the board’s analog pins: A1, A2, A3 e A4;

  4. Optionally, if you chose to use a button/switch to erase the drawing in Lousa mágica, it must be connected to the Digital 13 pin and 5V pin;

    If not using the D13 pin, connect the chosen pin terminal to the 10kΩ resistor (so called pull-down resistor) and to the GND pin simultaneously. The D13 has a built-in pull-down

  5. Now the software part, for drawing in the screen:

    5.A To use with Thonny IDE, py5 and pyfirmata

    5.A To use in the Processing IDE:

Arduino Nano example


Definitive setup suggestions

Other ideas

Alexandre B A Villares (, CC-BY-NC-SA-4.0 License Translated by Carolina Giorno