BICYCLE SPEEDOMETER

Tim Quinn

4/21/09

The Use of a Bicycle SpeedometerWith a speedometer

cyclists can know how

fast they are going

helping to maintain a

Constant

Speed or pace during their

ride. Another use for a

speedometer is the ability to

keep track and calculate the

distance that has been ridden.

Or an Odometer

Interest

Being a avid cyclist I wanted to apply my interest into my individual project by building something that I can make use of and that would be a fun and interesting project.

Hall Effect Sensor

Processor board, LCD driver board

8x2 LCD Display

Wiring Schematic

Transistor The Transistor is being used to

separate the power to the devices into, VDD(being powered all the time) and VCC(being turned on by the transistor) this will work as a power saving mode by turning off the parts of the circuit that use the most power, when not being used.

Hall Effect Sensor The hall effect sensor is being

powered at 3V by VDD, keeping it on all the time. As the Hall effect detects a magnetic pulse, the signal will work as a switch to turn on

VCC through the transistor. Hall Effect is going into PTA5

which is the MTIM port. MTIM in an internal 8 bit counter. I am using the counter to count the number of pulses from the Hall Effect in a given time period to find the frequency.

Board Layout

Code and Calculations

Speed = 2π f rRadios of the wheel = 1.148ftFrequency= the number of rotations in a given time period5280ft in 1 mile 3600seconds in 1 hour

Stop Mode

After 30 seconds of no input pulse the code will go to the inactivity_timer . This will turn off PTAD2 to the transistor, turning off everything controlled by VCC and going into stopmode. When the Hall effect detects the MTIM will start counting as well as PTAD2 turning back on.

Any Questions?