If you happen to’ve ever seen the type 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 reveals do not use typical film initiatives that expose your entire body without delay, however fairly a number of laser beams transferring in a short time to create the phantasm of strong 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 using an old hard drive.
Disclaimer: do not idiot round with lasers if you do not know what you are doing. It’s straightforward 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 completely 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 pace, Ben can create patterns within the horizontal traces. A stack of horizontal line patterns creates a whole 2D picture, similar to a monochrome CRT (cathode-ray tube) monitor. To make that every one come collectively, Ben simply wanted a strategy to spin the hub at a exact pace, and modulate the laser rapidly and sync it up with the hub’s rotational pace.
Ben used an Arduino Nano improvement board to manage all the things. 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 pace utilizing an infrared break beam sensor. The Arduino additionally modulates a strong laser diode utilizing a MOSFET to attain the speedy switching obligatory for this to work. Timing was essential, as a result of if the system ran too gradual then the PoV impact can be misplaced, however too quick and the Arduino would not be capable to sustain.
Ultimately, in fact, Ben was profitable and the end result 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 toes away from the projector.