Browse Prior Art Database

Bicycle Tachometer/Speedometer

IP.com Disclosure Number: IPCOM000082768D
Original Publication Date: 1975-Feb-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 77K

Publishing Venue

IBM

Related People

Mereness, TS: AUTHOR

Abstract

A digital display shows a bicycle's ground speed in miles per hour (MPH) or the crank speed in revolutions per minute (RPM).

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Bicycle Tachometer/Speedometer

A digital display shows a bicycle's ground speed in miles per hour (MPH) or the crank speed in revolutions per minute (RPM).

In Fig. 1, reed switches are mounted on the frame at points adjacent to the path of magnets attached to the crank and a wheel spoke. One reed is selected at a time by an RPM/MPH switch which also selects a timed interval corresponding to the metered quantity. For any bicycle, the number of crank reed closures (for one magnet and one reed) in 60 seconds indicates the number of crank revolutions per minute.

Similarly, the number of wheel reed closures in 47.7 seconds gives the indication of bicycle speed in MPH, or the number of wheel reed closures in 76.8 seconds gives the speed in kilometers per hour (KPH). Obviously, the timing interval can be reduced by providing more magnets or reeds. The RPM's are independent of bicycle size; however, the MPH/KPH timing periods are determined for a wheel with an outside diameter of 26.75 inches (typical racing wheel diameter).

In Fig. 2, whenever the selected reed switch closes, the single-shot SSA steps the counter +1. At the end of each timed interval, the counter's contents update a register, and the counter is reset to 0. Single-shot SSB prevents resetting of the counter while the register is being updated. The current register contents are continuously decoded and displayed.

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