An Introduction to Electric Bike Sensor and Controller
Frey Bike

If the motor, after a hundred years of development, has become the "soul" of the electric mountain bike, then the sensor and controller that work with the motor is undoubtedly the best assistant. They together made the electric bike get rid of the controversy of throttle and pedal and set foot on the development of Pedelec.

As mentioned in "The History of Electric Bikes", the coordination of the motor drive system is that when the cyclist pedals, the sensor is responsible for sensing the torque and cadence and sending monitored speed, cadence, torque, and other information to the controller. Then the controller controls the command of the motor by calculation. When subdivided, the operating principle of the sensor and controller is also worth exploring.



Sensor SR PA310.32.ST from Bafang

According to the EPAC (electrically power assist cycle) standard, electric bikes must be started by pedaling. When the pedaling is over, the e-bike also has to be stopped at once. The e-bike manufacturer needs to put a speed sensor on the pedal shaft, and add a sensor that measures the force (torque) that the rider puts on the pedal.

Although most of the users of e-bikes can change their speed autonomously, more often than not, electric bikes sense the pace and power of pedaling and then control the speed of e-bikes.

Source: bikegrade.com

The sensors can be classified into torque sensors and cadence sensors.

Torque sensor senses the strength when cyclists pedal. In this way, high-precision torque numerical value can be obtained, understand cyclists' riding intentions. While the cadence sensor is installed on the crankshaft set and consists of induction contacts and magnetic steel wire. It determines the demand for assistance by measuring the cadence. The faster the cadence is, the stronger the assisted power.

Like any system that needs to take concerted action, whether the performance of the electric mountain bike is good starts with whether the input signal is accurate. Generally speaking, the sensor is like the sensory system of the human body, the clear it is, the better your ability to judge will be. The torque sensor is more complex and precise than the cadence sensor. And by measuring the torque, it can provide a more accurate input signal for the work of the controller.

A high-quality electric mountain bike usually has more than a single sensor, but the superposition of the cadence sensor and torque sensor, and judges the current cycling state by comprehensive calculation.

Take Frey Evolve for example, the M510 motor has a high-precision torque sensor, which can accurately transmit the information of the rider according to the torque and cadence, and help the controller to judge and output assisted power.



The sensor accurately transmits the input signal to the controller. After receiving the torque, speed, and cadence signals, the controller obtains the output signal through the calculation to control the running speed, starting, stopping and other functions of the motor, guiding how the motor outputs.

Like the human brain, the controller can connect all the electronic parts of the electric bike, such as the battery, motor, throttle, display, and various sensors. It is responsible for tracking the pedal activity, battery voltage, motor power, acceleration and deceleration, and other important functions.

Source: elecycles.com

In addition, the controller also provides some fundamental protection functions, such as high voltage protection and low voltage protection of the battery, to prevent the battery from being overcharged or over-discharged. It monitors the temperature and current of the motor and ensures the safety of cyclists by brake protection.

The controller also has a difference between a sine wave and a square wave, each of which has its advantages and disadvantages, which will not be explained in this article. Many electric mountain bike players will choose to replace the controller to pursue higher speed. But the controller's wiring lines are complex, and need professional knowledge as an auxiliary, so novices had better not try easily.

Complex wiring lines

The algorithm of the controller is what we call the controller program, which is also called the "invisible hand of God" by our technology department.

For example, Frey Evolve has Eco (the most economic mode), Tour (the most comfortable mode), Sport (the sport mode), Sport+ (the sport plus mode), and Boost (the strongest sport mode). The selection of power assist gear determines the power when riding, which depends on the role of the controller program.


Again, We sincerely hope you can Free Ride& Enjoy Yourself!

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