This is my second Kickstarter Project and builds upon the theme of the Western Zodiac. My first one was Aquarius which is a stroboscopic fountain lamp and can be found here:
I used what I learned from Aquarius and applied it here for the Pisces project. A rotating string can demonstrate standing waves (something that a water stream cannot do) which I thought would be an interesting change and look from Aquarius. I went through several different iterations of what the "shell" housing this "science experiment" would look like:
The final shape I arrived at was representative of the Pisces symbol as well as functionally sound and stable.
The LEDs strobe at a 10-90 duty cycle ratio (that is, they are ON for 10% of the time and OFF for 90% of time per PERIOD). I vary the strobing frequency/period with one of the potentiometers to create different effects. The other dial selects the color modes (over 10 built-in). The LEDs used were APA102Cs (not the typical WS2812Bs that everyone uses). Reason being is that the WS2812B max refresh rate is not high enough to create strobing effects (On-Off) without flickering issues. The APA102Cs are undoubtedly more expensive but have much higher refresh frequency so that it can handle Persistence-of-Vision type of applications.
The string spins at a constant speed since it's being fed by 3.3V (nominal 5V). This keeps the sound low and prolongs the life of the motor. The motors will eventually have to be replaced after a few years of normal usage and I do include replacement motors as part of the package.
One of the first issues I encountered was that the string will eventually twist up over time (even if both motors are running at the same voltage (one in reverse), minute manufacturing differences exist to throw the string off course. I designed a small pivoting hook for the string to mount onto thus preventing that issue from ever happening. The pivot hook allows the string to free-rotate and essentially self-correct itself if it ever gets wound up too much. This was 3D printed and due to its shape, cannot be injection molded.
Another issue is that while I encourage people to touch the string as its moving, it WILL degrade it. Because the string rotates at 75-ish times per second, touching it means the string is "grazing" your fingers at the same frequency. That "chafing" of the string causes it to fray and eventually unravel/break. I've designed the pivot hooks in a way that allows new strings to be swapped in easily.
The frames and base were 3D printed using ABS filament though if the campaign is successful, it will be injection molded to save on costs and time.
For prototyping purposes, I used a protoboard and mounted an Arduino Nano PCB along with some other required components. The 2 potentiometers that control the color selection and the strobe frequency. A buck converter (step down) to take the unregulated 12V input voltage to 5V for the LEDs and DC motors. The final version will use a properly manufactured PCB of course.
While its a fairly straightforward design and effect, keeping the costs down for manufacturing was difficult. The odd shape makes injection molding extremely expensive, especially in North America (I got quotes from ProtoLabs). Depending on the finish, it ranges from $7K USD to $20K USD for the frames and the base. I would prefer a high gloss finish which is the second most expensive finish available ($18K USD) as this would be an aesthetic...Read more »