Top: Fully assembled communicator Bottom: LED Array on main housing (faces behind bicycle)
I frequently go bike riding with my girlfriend and we like to switch off between who leads and who follows. We tend to alternate even when we try out new routes that only I am familiar with. When I am following on a new route I often try to shout out instructions for turns that can’t be heard by the biker in front, and as a result we miss our turns from time to time. My idea was to use arduinos, wireless radios, pushbuttons, flex sensors and a power system to create a functioning, self-powered bike signaling platform.
What it does:
This system allows 2 riders on the move to send and respond to requests for left and right turns in addition to stops. User input is taken from buttons, which are mounted in 3D printed housings that rest near the handgrips on each bicycle's handlebars. Wireless communications are sent through a 433Mhz LoRa radio transceiver controlled by a microcontroller. Turns are detected through flex sensors that enable the system to reset both the front and back lights to reflect the successful completion of agreed upon turns. The rotary motion of the back wheel is harnessed by an alternator, which powers the entire system.
How our team built the communicators:
This project was built in modular sections as a team effort. The custom housing design and 3D printing was an iterative process involving matching electronic components and bicycle fit. The power system was constructed by hooking up an AC generating alternator to the back wheel. The AC produced by the alternator is subsequently converted to DC through a rectifier and is knocked down to the desired 5V DC using a voltage regulator. The 5V DC line is adapted to a micro-usb connection and subsequently fed into the microcontroller to charge the attached Lipo battery. The array of LEDs on the back and corresponding LEDs on the front of each bicycle are controlled with transistors. The turn sensing system was constructed by hooking up flex sensors in independent wheatstone bridges. Each wheatstone bridge is sampled by a comparator (that performs analog to digital conversions outside of the microcontroller) to determine if a turn is in progress. The communication system was implemented using the arduino Radiohead library. All system logic was written in C. These independent systems were brought together to produce a functioning, self-powered bicycle communication platform.
Challenges I ran into:
One of the largest challenges I encountered with the design was waterproofing all of the components. Given that the bicycles using the communicators might unexpectantly get caught in the rain, waterproofing all of the electronics seemed essential. This was addressed with some creative design of the 3D printed enclosures, Silicone caulk and deconstructed nitrile gloves. Another challenge was installing the alternator in a configuration that would allow it to either be in contact with the wheel (generating power) or not generating power. The reason for this dual configuration was that once the battery powering the microcontroller and supporting electronics was charged, there was no need to retain the added pedaling resistance of the alternator. Additionally, constantly charging a fully charged battery seemed like a bad recipe for a long product lifespan... Being able to move the alternator between the two configurations was straightforward, but what proved challenging was keeping constant tension on the alternator, so that changing its position would not loosen its connection to its mounting bracket. Installing a heavy spring between 2 washers allowed the alternator to retain its desired position and be rotated without becoming loose.
Accomplishments that I’m proud of:
This was my first time working on an electronics/programming project in a group and I really enjoyed helping my team members learn about new technologies and collectively create a functioning product. The knowledge I relied on to create the design and implement the communicators was self-taught and I feel great being able to put this technical understanding into practice.
What I learned:
Working in a team is fantastic! While I really enjoy working on hobby projects by myself, it is a lot of fun to have an entire team working together for a common goal. I also learned a lot about 3D printing during the planning and creation of the communicators and look forward to continue 3D printing my own prototype components in the future.
What’s next for the Wireless Bicycle Communicators:
I am interested in adding a single rider mode to enable a lone biker to use the lighting system to signal turns to nearby vehicles without requiring responses from another rider. I am also interested in trying to reduce the power consumption of the communicators by putting the radios and microcontrollers to sleep at defined times. Finally, I intend to try to push the limit on the distance these wireless transceivers are capable of broadcasting by testing their functionality with varying directional antenna configurations.