Previous posts

Post 1 - Introduction

Post 2 - Installing OpenCV - Prerequisites

Post 3 - Installing OpenCV

Post 4 - Installing Pygaze

Post 5 - Installing eye tracker

Post 6 - SPI communication

Post 7 - SPI communication in Python

EyePrints - Post 8 - Getting started with Kinetis

EyePrints - Post 9 - Mechanical design

EyePrints - Post 10 - Mechanical design: the plotter

EyePrints - Post 11 - Eye tracker software

EyePrints - Post 12 - Getting started with the kit

EyePrints - Post 13 - KDS Project

EyePrints - Post 14 - The drawing board


In this post, I will show some pictures and video of the plotter

The plotter has a servo that can lift the pencil when the painter wants to move to another area without drawing anything on the board


The servo is controlled by a small Python script


import RPi.GPIO as GPIO

To put down the pencil, the start method of the pwm object is invoked


To lift the pencil up, the start method of the pwm object is invoked with different values


Both values (7 and 5.5) has been determined empirically. The second invokation of the start method (pwm.start(0)) is required to "stop" the servo. The PWM signal generated by the Rapsberry Pi is not very stable, so the servo keeps on correcting its position. The pwm.start(0) function prevents the servo from moving continuously around its final position



Here is the plotter with the pen in the "up" position



And here is the pen in "down" position



Finally, here is a video of the plotter in action