I was never really a He-Man fan as a kid, I always had a preference for Thundercats. However, Masters of the Universe is a considerably good live action movie that stands on its own merits.
The movie introduced me to the Cosmic Key, a device that can open a portal to any point in time and space, through the use of musical tones. As Gwildor (the device's inventor) explains in the film, the universe is music.
The original prop for the film is one of the greatest movie props every created. It was made from steel, brass, aluminium, resin and filled with gears, motors and drive shafts, it reportedly cost over $150,000.00 to build, though I'm expecting to build mine at a considerably reduced cost. This project is likely to be the most complicated piece of mechanical engineering I have ever challenged myself to design.
I started this project with the design of the electronics, I'm utilising the Raspberry Pi as the main controller. For my first test I created a simple Python script, using the Pygame sound module I have been able to play 7 piano notes (A,B,C,D,E,F and G) through the Pi's audio jack. This will soon be updated to included 64 unique individual notes, replicating the sound of the tones used in the film. I added an I/O expansion board, utilising the Pi's I2C port this will give me the 64 I/O ports I need.
I added the Adafruit MAX98306 amplifier to output the sound to a HiWave 5w/4Ω speaker, it's not as loud as I'd like but I need to keep power consumption to a minimum (the amp only draws 2mA). This is also a Class-D amplifier, which means it virtually runs cold, which is a must in the compact and tightly packed enclosure of the Cosmic Key.
I built a power distribution board to power the Raspberry Pi, the Adafruit amp and the Servos, it's fitted to the back of the Pi. This utilises a rechargeable four-cell 7.4v 5200mAh Lithium-Ion re-chargeable battery that is fed through a 5v switching-regulator. A SPDT toggle switch is used to switch between ON and OFF/Recharge, the circuit is also fused for added protection. On the first design the switching regulator got fried, so I amended the design to include a diode for added protection as well as a capacitor on both sides of the regulator to smooth the current.
I'm still in the process of 3d modelling the enclosure, the bottom section is near enough complete apart for some tweaking. I have also revised the design of the base as my first version was not accurate. The internal assemblies that mount the Raspberry Pi, battery, amp and speaker are complete, so I'll soon be moving on to modelling the top section of the Key. This is where things really start to get complicated as I have to house the motor, servo, and gears to enable all of the mechanical actions.