If you happen to’ve ever seen the sort of laser present with projected animations, just like the well-known one projected onto Stone Mountain in Georgia, then you definitely’ve skilled persistence of imaginative and prescient (PoV). These exhibits do not use standard film tasks that expose your complete body without delay, however fairly a number of laser beams transferring in a short time to create the phantasm of stable traces. Conventional laser projectors depend on mirror galvanometers, that are tiny mirrors that pan and tilt at ridiculous speeds to direct the laser beam. However Ben took a unique method for his DIY laser projector by utilizing an outdated onerous drive.
Disclaimer: do not idiot round with lasers if you do not know what you are doing. It’s simple to blind your self or others, and even to start out fires.
As a substitute of reflecting the laser beam off of a single mirror galvanometer that might transfer the beam round within the X and Y axes on the projection floor, Ben used a number of mirrors mounted to a single spinning hub. Every mirror sits at a barely totally different angle, so the primary mirror would possibly replicate the beam up at a 10-degree angle, the final mirror tilts the beam down at a 10-degree angle, and the mirrors in-between tilt the beam at common intervals from one excessive to the opposite. Because the hub spins, the beam displays off of the mirrors to venture a number of horizontal traces on the projection floor.
By modulating the laser beam at a excessive velocity, Ben can create patterns within the horizontal traces. A stack of horizontal line patterns creates an entire 2D picture, identical to a monochrome CRT (cathode-ray tube) monitor. To make that every one come collectively, Ben simply wanted a method to spin the hub at a exact velocity, and modulate the laser rapidly and sync it up with the hub’s rotational velocity.
Ben used an Arduino Nano improvement board to manage every thing. It receives the textual content to show from a smartphone through a Bluetooth module. The mirrors connect to a 3D-printed hub spun by a tough drive motor and the Arduino screens its velocity utilizing an infrared break beam sensor. The Arduino additionally modulates a strong laser diode utilizing a MOSFET to realize the fast switching obligatory for this to work. Timing was necessary, as a result of if the system ran too sluggish then the PoV impact could be misplaced, however too quick and the Arduino would not have the ability to sustain.
In the long run, after all, Ben was profitable and the consequence could be very spectacular. The laser is highly effective sufficient that Ben had no bother projecting textual content onto a fence in his yard that was 90 ft away from the projector.
