Bike Totem

OBJECTIVE // To build a device connected to your bike that would display the live motion of your riding to a desktop totem in a loved one’s home so that when your loved one goes out for a ride, you see the motion and are reminded of them.

BACKGROUND // For my Smart Products class at Stanford we were tasked with building a device to help encourage positive healthy activity during the COVID quarantine. We had a limited selection of electronic components provided for use to utilize WiFi connectivity, but we decided to go in a different direction and utilize a cellular connected board and a wheel generator.

INGREDIENTS //

……………(1)  Cellular connected Microcontroller (Particle Electronic)

……………(2) Hall Effects Sensor

……………(3) Hub Mounted Bike Wheel Generator

……………(4) Continuous Motion Servos

……………(5) WiFi Connected Microcontroller (Particle Photon)

TEAM // Mechanical Engineer & Electrical Engineer

DETAILS // The pair of devices utilized a simple one way communication scheme where the client running on the bicycle measured the velocity of the bike using a wheel mounted magnet and a hall effects sensor. This velocity was then communicated to a webserver via a cellular chip of which the totem was monitoring. When there was a positive velocity registered, it would map this to the speed of the wheels on the miniature bicycle.

The latency on the startup is a result of the power mechanism utilized to run the bicycle mounted hardware. Though there was a small LiPo battery providing power for the hardware, this was powered by a bike hub generator that produced electricity when the bicycle was moving. As a result, the user doesn’t need to charge any batteries, but it requires a short period for the bike to produce enough energy to run the microcontroller. Subsequent starting and stopping after the device has received some power will cause less of a delay as there will already be power.

When the bike starts moving, it first requires the hub to produce enough power to energize the microcontroller. It then needs to connect to the cellular network to transmit the current velocity. It is worth noting that the cell network in our neighborhood in Moss Beach is extraordinarily weak so this adds to the latency. The WiFi module then reads this value from the server and converts it to a local velocity on the totem.