Design and Implementation of an Electric Bicycle based on Microprocessors

W.-S. Jwo, C.-C. Tong, and J.-G. Huang (Taiwan)

Keywords

Electric Bicycle, Permanentmagnet Motor, Leadacid Battery, PWM control, Battery Charger

Abstract

This research exploits a dedicated electric bicycle. This electric bicycle is made of seven major parts: (1). Micro-controller unit, (2) Speed control and motor driver, (3) Transducers, (4) Battery recharge circuit, (5) Battery management part, (6) Real-time monitoring system, and (7) Battery and electric motor part. The brain of this vehicle is composed of two microprocessor chips. EM78P447S is the main control unit accompanied with EM78P458 as the auxiliary-controller. Both of these chips are products of E-LAN Microelectronics Corp.. Speed control is achieved by the PWM technology design, the control signal is fed directly from EM78P458 after calculation, and the motor driver is using power MOSFET as the driving element. Hall effect transducer is used to monitor the motor driver current. The battery residual capacity is estimated by the open-circuit voltage test and the Coulometric measurement method. One temperature IC is required to protect circuit from overheating. LCD screen is design for real-time display speed, mileage and battery capacity remains. This electric bicycle is using a permanent-magnet motor as the main power driver and lead-acid batteries as the power supply. This work was carried out with some special considerations such as: no air pollution, high safety, inexpensive cost, long driving ability, informative LCD display, and stable speed control. A prototype is built and tested. All the experiment results are very inspiring. The overall cost is less than US$200. The speed is limited to 30 km/hr and maximum travel distance is 29.3 km under cruise control without battery recharge. Whenever the electric bicycle's speed keeps steady for more than 10 seconds, the bike can switch to cruise control mode automatically and this speed is treated as the set point for that duration. Automatic power-off is programmed to turn off the bike's power to save energy if it were idle for over 5 minutes.

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