Laser Spirograph

thingiverse

Laser Spirograph (A Whimsical Tree Topper) BEWARE: Only use lasers with a power output of no more than 5mW (Class IIIa) for this device, as its safety has not been thoroughly tested beyond that threshold. Using a stronger laser can cause permanent vision loss if the motor drivers stall and the beam is directed at your eye. This warning cannot be overstated. https://www.youtube.com/watch?v=p59LU9QrhCM BOM: Two vibration motors are required, which can be sourced from Radio Shack (https://www.radioshack.com/products/radioshack-3vdc-micro-vibration-motor?variant=5717362821). A laser module with TTL control is also necessary; a 100 mW unit can be obtained from eBay or the equivalent model: http://odicforce.com/epages/05c54fb6-7778-4d36-adc0-0098b2af7c4e.sf/en_GB/?ObjectPath=/Shops/05c54fb6-7778-4d36-adc0-0098b2af7c4e/Products/OFL194. Square mirror tiles, similar to those found in craft stores, will be used for the laser's projection. An Arduino Pro Mini is recommended due to its versatility and ease of use. The choice between SpiroMount5 and SpiroMount10 depends on the desired throw distance; SpiroMount10 provides a wider angle (10 degrees vs. 5 degrees) but requires more power. How it Works: Each motor's power is treated as a vector coordinate, determining how fast each motor spins. The power is continually modified by an "inertia" that changes signs and magnitude when the maximum or minimum allowed power is reached. This ensures a smooth, dynamic pattern. At startup, both motors are set to maximum power for half a second before the laser is turned on. At low powers, the motors can stall; therefore, each motor has a designated stall speed. If both motors' power falls below this threshold for two cycles (3 seconds), one motor will be randomly kicked up to maximum speed for 1.5 seconds. Please note that using this device in public with a laser exceeding 5mW requires a CDRH permit or variance. To obtain the necessary permit, independent stall detection must be implemented; if either motor stalls, the laser beam should be cut off immediately to ensure safe operation. This measure is crucial for compliance and should be integrated into the code as soon as possible.