[Mykle Hansen] explains how to make a Speed Vest displaiyng the speed of the bicycle, as seen on Make: 19. This is a cool intro-project for wearable electronics.
Bicyclists receive a lot of honk-based grief from car drivers who perceive them as slow and in the way, and when drivers misjudge a bicycle’s speed, it can cause “right hook” collisions that kill several bicyclists each year. This lightweight night-cycling vest displays your current speed in glowing, 7-inch-tall numbers easily visible to cars. On the back, an Arduino microcontroller reads input from an off-the-shelf bike speedometer sensor, and then switches power to sewn-in numerals made from electroluminescent (EL) wire.