To provide more torque adjacent coils are paired and turned on and off together - doubling the current available to turn the shaft. Motor control is handled via gpiozero powering GPIO pins as simple digital outputs (.
The motors are powered from 4xAA batteries (6V). The Etch-A-Sketch wheels are driving using two 5V 28BYJ-48 motors, driven using ULN2003 ICs. On the Etch-A-Snap this is detected by a tilt-switch which resets the camera to “ready to take” mode. To clear the screen you flip the Etch-A-Sketch over and shake it gently - this coats the reflective powder back onto the reverse of the screen, making it appear silver-ish again. There are no other controls on the standard Etch-a-Sketch. Rotating the left hand wheel moves the plotter point left and right (CCW and CW respectively), while the right hand wheel moves the plot point up and down (CCW and CW respectively). The plotter is controlled using two input wheels. Lines are produced by scraping this powder off with a little nubbin which is moved around on wires.
The dark lines are actually ‘gaps’ in a reflective powder coating which sticks to the reverse side of the glass screen. In this part we’ll look at how to take this image and generate the draw instructions for the plotter.Įtch-A-Sketch is a very simple 2D plotter which is limited to drawing a single unbroken line, of a single thickness on a semi-reflective screen. So far we've built the Etch-A-Snap and processed an image to produce a 1 bit image.
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