Design Con 2015

Wireless bicycle brake light

-April 17, 2014

 
Presenting one of the runners-up in the TI LDC1000 inductive sensor design contest.


My submission video shows the new Texas Instrument's LDC1000 attached to the rear wheel fork of a bicycle, where it senses the spokes as the wheel rotates. This proof-of-concept demonstration shows how perfect this sensor is for my goal of an improved bicycle brake light that has many advantages. I'm passionate about getting this invention completed and on the market as soon as possible, where it can help prevent some of the many injuries and deaths to the hundreds of millions of the world's bicyclists each year.

My first LucidBrake invention used a 3-axis accelerometer, plus a complicated microprocessor algorithm to detect bicycle deceleration while eliminating most bumps, rotations, and variable mounting angles. It works, but it's not perfect, and in my quest for something even better I've often asked myself "How can I detect velocity directly, without having to do all these problematic and inexact calculations from the acceleration data?"

With perfect timing, the new LDC1000 inductance to digital converter from Texas Instruments provides the ideal solution!

As shown in the video, with no adjustments to sampling rate, or any of the other register settings, the TI LDC1000 worked perfectly to detect spokes as they transition near the sensor. During the industrial design and engineering that will be required to bring this invention to market we'll optimize the settings, the coil shape, size, and other details, but I was thrilled when it worked "as is" right out of the box!

So why do I consider this to be the perfect answer to my quest for building the perfect bicycle brake light? Consider these facts: No optics to get dirty. No expensive rare earth magnets. Nothing needs to be added to the bicycle's wheel in any way to detect rotations. No wiring to the bicycle's braking system at all. Just attach it to a rear fork... and it just works!

The sampling rates available on the TI LDC1000 provide hundreds to thousands of readings for each spoke's transition near the sensor, even for the fastest bicycles. The threshold output on the INT pin provides the perfect way to determine very accurate bicycle velocity - a simple microcontroller count between pulses does the trick. When velocity is decreasing at a significant rate, the brake light comes on. Couldn't be simpler! This will work independent of hills, slopes, or bumps, providing an instantaneous and absolutely perfect way to light the ultra-bright brake light LEDs when the bicycle is slowing down.

 
Sensing Design Challenge 2013 winners:


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