T t t set timer to go off at each edge start timer

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: start timer running / ) $ $ 1 42 Change value of “on” time to change analog average Need to determine the rear wheel velocity average output = ( on + off ) / ( period ) Use sensor to detect wheel moving How do we decide on the period of the pulses? Using two timers Determine speed of a bicycle Attach baseball card so it pokes through spokes Number of spokes is known Count clicks per unit time to get velocity One to set period (auto-reload) One to turn it off at the right duty cycle Baseball card sensor is a shaft encoder click! t bike wheel baseball card set timer to go off at each edge start timer running How many segments should be used? Instead of spokes we’ll use black and white segments Black segments absorb infrared light, white reflects Count pulses instead of clicks wheel infrared light emitter detector More segments give finer resolution Fewer segments require less processing Tradeoff resolution and processing pulse " ' 3 5 Use interrupt on GPIO pin Microcontrollers come with built-in I/O devices Every interrupt, increment counter Timers/counters GPIO ADC Etc. Use timer to set period for counting When timer interru...
View Full Document

This document was uploaded on 04/04/2014.

Ask a homework question - tutors are online