Bonobo Lights
Bonobo lights are a tool for fun, safety and personal expression when riding bicycles at night.
You clip them on your bicycle spoke, then ride along. Enjoy this video to understand more!
If you are pressed for time you can also watch the 1-minute presentation video summary that I made for the project review.
If, on the contrary, you have plenty of time and you are interested in the blow-by-blow account of how I developed this project, go ahead and check out the project development page.
Prior Art
This project relies on the Persistence Of Vision (POV) effect. POV displays are a whole category of DIY projects.
Spoke POV
The only other bicycle POV project that I was aware during development was Spoke POV, made by @ladyada herself! It was made about a decade ago, and it shows. It uses many more components, it's very bulky, only does monocolor LEDs, and can only be seen from one side.
You can read more details about prior art in my Application and Implications week page.
BikeBeamer
The very day after I presented my project at Fab Academy, a post about BikeBeamer came out in Hackaday. It's the same idea, only it uses a more powerful processor. I prefer my mounting system because it does not rely on one-use zip ties for the spoke unit.
I also managed to get a single strip to be seen from both sides! Neither BikeBeamer nor Spoke POV managed that.
Components and modules
LEDs
The core of the system is a strip of APA102-compatible addressable LEDs. I initially went for an in-house LED matrix multiplexing design. It worked great as a proof-of-concept and to get me started with electronics design and programming. This culminated in a succesful test in week 14. That's a moment I'll remember.
That breakout board had 4 "columns" and 4 "rows" for multiplexing 16 red LEDs. I started designing a 24 RGB LED version (6 columns, 12 rows), but it got daunting pretty quickly. That's when I moved to addressable LEDs. I chose to use a 32-LED long section from a dense strip of 144 LEDs/meter. This should work on many different bicycle wheels and provide as high a resolution as is currently possible.
If you want to build your own, you'll have to cut it out from a 1- or 2-meter strip, then possibly solder a 4-pin JST connector. It should look like this:
Board
The spoke controller is a SAMD21E18A-based board. The full KiCad project is available, including rendered pngs and Mods-generated Gcode for milling in a Roland SRM-20.
The first mountable version was called board 03, and I made it on week 15
I designed board 04 in week 17. It was integrated with the "next-generation" mounting system, which I designed the same week. This is the version that went into the "v1" Bonobo Lights, the one I presented for graduation.
The core components of the board are the MCU (an ATSAMD21E18A) and an analog Hall-effect sensor that detects a neodymium magnet that is installed in the bicycle fork as a reference.
It also has 2 high capacity electrolitic capacitors to smooth out power supply, since the LED strip can vary in power consumption from around 1A to zero very quickly.
It connects to the strip through a 4-pin JST connector and to the powerbank through a USB mini.
Mounting System
The mounting system is responsible for system integration. It holds the LED strip and the board. It connects to a spoke in the bicycle through tabs on its trailing edge. On its leading edge it has a single tab that connects to another spoke through a rubber band. This allows the system to stay aligned with the plane of the wheel and to adapt to many possible spoke configurations.
It's printed in a single piece in any regular 3D printer. I highly recommend printing this in a strong plastic. I chose PETG and it works great. Color is up to you, but I chose translucent PETG and I thing it looks amazing when it lights up.
I went through many iterations and experiments, mostly on weeks sixteen and seventeen
The Rhino file for v9 mounting system and STL file for v9 mounting system are available for download.
Power source
For now, the power source is a simple user-provided PowerBank. This provides power, battery regulation, and charging capability. It has to be mounted on the wheel, as firmly as possible and close to the hub.
Magnet
A regular neodymium magnet. Needs to be attached to the fork of the bicycle, as a reference.
Software
The software is fully open-source. The project repo is hosted at github. Contributions are welcome!!
Bill Of Materials
Budget
| 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 |
Full List of electronic components for assembly
References correspond to those in the KiCad Project. If you have access to the Market at a Fab-Academy participating fab lab, all of these should be available there and you can just go and pick them up.
| Reference | Value | Qty |
|---|---|---|
| C1,C5 | 100nF | 2 |
| C2 | 1uF | 1 |
| C3, C4 | 100uF | 2 |
| D1,D4 | RED LED | 2 |
| D2,D3 | GREEN LED | 2 |
| D5 | BLUE LED | 1 |
| J3 | SWD connector: 4 pin | 1 |
| J5 | TH HALL SENSOR | 1 |
| P2 | USB Mini Connector | 1 |
| R1,R2 | 10k | 2 |
| R3 | 22R | 1 |
| R4,R9 | 10R | 2 |
| R5,R8 | OPTIONAL: I2C pull-ups (5K) | 2 |
| R6, R7 | 1k | 2 |
| SW1,SW2, SW3 | Switch_Tactile_Small | 3 |
| U1 | ATSAMD21E18A | 1 |
| U2 | 3.3V 1A voltage regulator | 1 |
All design files
- Rhino file for v9 mounting system
- STL file for v9 mounting system
- full KiCad project
- Compressed software repo at the time of project delivery
- The project repo at github.
Instructions
- Gather components and board
- Solder
- Burn bootloader
- Desolder JTAG connector
- Program
License
This work is licensed under CC BY-NC-SA 4.0
This license requires that reusers give credit to the creator. It allows reusers to distribute, remix, adapt, and build upon the material in any medium or format, for noncommercial purposes only. If others modify or adapt the material, they must license the modified material under identical terms.
If you want to commercially distribute Bonobo Lights or a derivative product, contact me for terms.