Applications and Implications
Task
Propose a final project masterpiece that integrates the range of units covered.
Your project should incorporate:
- 2D and 3D design
- Additive and subtractive fabrication processes
- Electronics design and production
- Embedded microcontroller interfacing and programming
- System integration and packaging.
Where possible, you should make rather than buy the parts of your project.
Projects can be separate or joint, but need to show individual mastery of the skills, and be independently operable.
See Final Project Requirements for a complete list of requirements you must fulfil.
Bonobo Lights
Bonobo lights are an open-source Persistence Of Vision (POV) display for bicycle wheels.
They consist of a single strip of RGB LEDs that attaches to the spoke of a bicycle's wheel and turns on and off precisely as they roll in order to display an image or video through the Persistence of Vision (POV) effect.
What will it do?
It will show images on your bike at night through the POV effect.
Prior Art
A Californian company called Monkeylectric used to make a series of products called Monkey Lights that fit my vision exactly. However, their Amazon store is deserted and their YouTube channel last posted a video in 2020.
There are at least 2 similar products in Aliexpress, at least one of which actually seems to improve on the original. The other is impossibly cheap. There is someone selling the original as well.
Persistence of Vision displays seem to be a whole category of DIY project.
Spoke POV
The only one that I've been able to find that is both A) open-soure and B) meant for bicycle use was made by @ladyada herself a while ago now: Spoke POV
Adafruit carried kits for a while, but they're discontinued now. On closer inspection, it turns out it was Adafruit's product #5! And there are not remaining signs of products #2, #3, or #4. Interesting piece of computing history!
It's interesting to compare the compactness and complexity of both. Especially considering that the simple, compact version was made by a middling amateur like me and the other one was designed by a gifted electrical engineer.
I can't help but think I'm lucky to get into the field now, 13 years later.
It's probably fitting that the key advance here that allowed to simplify the project are addressable LEDs. I don't know if Adafruit were the inventors of them, but they've definitely been a huge factor in their popularization through the Neopixel brand.
What will you design?
- PCB: milled, soldered
- Mount: PETG, 3D printed
- Software
What questions need to be answered? How will it be evaluated?
The main question in my mind was whether addressable LEDs can provide the required frame rates or not. I've pretty much answered it with a definite yes, although it's quite likely that more performance could still be juiced out of them.
The final project will be evaluated by:
Central criterion: Can it use the POV effect to produce the illusion of a full image on a bicycle wheel as the wheel turns?
Additional criteria:
- Can it show more than one image?
- Is it easy to attach/detach from the bicycle?
- Is it easy to use (turn on, off, select patterns...)?
- Is it robust enugh to survive many bicycle trips?
- Is it compact?
- Is it aesthetic?
- Does it have long battery life?
Key materials and components
Addressable High-Density RGB 144-LED Strip, 5V, 1m (SK9822)
I expect the cost of materials for a single unit to be around 35€:
- 15€ for the LEDs
- 4€ for the MCU
- 10€ for an off-the-shelf power pack.
- 6€ for the rest: other electronic components, PCB, PETG.
| Item | Provider | Link | Quantity | Price/unit | Total Price | Comments |
|---|---|---|---|---|---|---|
| Addressable High-Density RGB 144-LED Strip, 5V, 1m (SK9822) | Pololu | [Pololu] | 0.25 | €55.71 | €13.93 | Quote in dollars. One meter is enough for 4 Bonobo Lights, with some LEDs to spare. |
| Power Bank | Media Markt | [Media Markt] | 1 | 10 | 10 | Any Powerbank with >2A output should be enough. Capacity is usually too big. |
| Board | Self-milled or JLCPCB | 1 | 2 | 2 | ||
| ATSAMD21E18A | Digikey | [ATSAMD21E18A] | 1 | €3.71 | €3.71 | MCU |
| JST 4-pin connector | [Diotronic] | 1 | 1 | 1 | ||
| Electronic components | Mostly Digikey | 24 | 0.2 | 4.8 | See detailed list of components. Estimated average price 0.2€ | |
| Grand total | €35.44 |