Cyclocomputer

A basic cyclocomputer with a wheel speed sensor may display the current speed, average speed, maximum speed, trip distance, trip time, total distance traveled, and the current time. More advanced models with additional sensors and storage may display and record altitude, incline (inclinometer), heart rate, power output (measured in watt) and temperature as well as offer additional functions such as pedaling cadence, a stopwatch and even GPS navigation and video data overlay synchronization. They have become useful accessories in bicycling as a sport and as a recreational activity.

The display is usually implemented with a liquid crystal display, and it may show one or more values at once. Many current models display one value, such as current speed, with large numbers, and another number that the user may select, such as time, distance, average speed, etc., with small numbers.

The head usually has one or more buttons that the user can push to switch the value(s) displayed, reset values such as time and trip distance, calibrate the unit, and on some units, turn on a back light for the display. Most displays are navigated by pressing buttons and high-end models use a capacitive touch screen to navigate screens and maps.

The older, traditional sensors have a magnet attached to a spoke of either the front or rear wheel. A sensor based either on the Hall effect, or on a magnetic reed switch, is attached to the fork or the rear of the frame. The sensor detects when the magnet passes once per rotation of the wheel and time stamps or time codes the revolution count. Alternatively, a sensor may be attached to the wheel hub. Distance is determined by counting the number of rotations, which translates into the number of wheel circumferences passed. Speed is calculated from distance against lapsed time period using the circumference of the wheel and the time it took to make one rotation.

To measure cadence (revolutions per minute of the crankarm), a magnet is mounted to the crankarm, and a sensor mounted to the frame. This works on the same principle as the speedometer function and measures the turning of the cranks and front chain ring.

Some models use a wired connection between the sensor and the head unit. Other cyclocomputers, e.g. those used by competitive cyclists, transmit the data wirelessly from the sensor/transmitter to the head unit. Data can be exported to a SD card, computer, or phone and uploaded to an internet web service. Wireless cadence and speed sensors use wireless communication standards ANT + and Bluetooth Low Energy and can directly communicate with a smartphone application that also uses the phone's GPS, barometer, temperature, clock, and other sensors to create a more detailed picture, record, or map.

Bicycle speed in km/h

For integrated shifters on racing bicycles, the gear can be read by the computer: Shimano's Flight Deck and Campagnolo's ErgoBrain work with their respective systems to detect the gearing. This allows indirect measurement of cadence. These systems do not have sensors on the crankset or cassette to determine what gear the bicycle is in. They work exclusively with the shifters, which may result in misleading information. Instead of knowing what gear the bicycle is in, they rely on sensing when the cyclist changes gears using sensors in the shifters. If the gear change doesn't actually happen, or the computer's sensors are too sensitive (e.g.: when braking with STI-style shifters), the information displayed is not accurate.

With additional sensors, other performance measurements are available:

• A heart rate monitor can be integrated into the computer, using a chest strap sensor.
• A power meter measures power output in watts, using a torque sensor in the bottom bracket, pedals, or rear hub.

Some models also have sensors built into the head that measure and display environmental parameters such as temperature and altitude.

Some more sophisticated models are able to measure the rider's power in terms of watts. These units incorporate elements that measure torque at the crank, or rear wheel hub,[7] or tension on the chain.[8] This technology began in the late 1980s. (See Team Strawberry for the early development and testing stages of this technology.)

Some cyclocomputers (such as the Garmin Edge, trimm One, Wahoo Elemnt Bolt or Hammerhead Karoo) can be loaded with maps and can thus show the rider's position on the map, or provide turn-by-turn directions for a pre-determined route.

Most electric bicycles have a microcontroller in the motor controller to calculate input cadence or torque, adjust amperage, control the motors and send the display screen information. Often cyclists can select the level of power assist provided using the computer. The computer also monitors the speed and can deactivate the motor for braking or if required by law (for example, in many countries pedelec bikes cannot use motor assist above 25 km/h).