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  • Digital Bicycle Speedometer

  • Created: Apr 03, 2017

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This speedometer is built with the latest Littelfuse product, the 59140-miniature flange mounting reed sensor. Its case design enables screw or adhesive mounting and capable of switching up to 265 VAC/300 VDC at 10 VA. On this project, the 59140 reed switch is set up to the fork of the bicycle paired with the 57140 magnetic actuator screwed to the wheel of the bicycle.

The project is built around an Atmega328 AVR microcontroller, and programmed using the Arduino IDE. A 555 timer is configured as a de-bouncing circuit in between the sensor and the microcontroller. A 10kΩ resistor is connected from the supply to RESET pin of the MCU for normal operation and a momentary-on push-button switch is connected to ground for reset. An external 16MHz crystal oscillator with two 20pF capacitors is used for accurate timing. An 8x2 character LCD is used to display the speed and distance. It is connected to the MCU via four data line for 4-bit mode. And lastly, we need a regulated 5V power supply for all the components.

This digital speedometer is just one of many things we can think of applying the 59140 reed sensor. The sensor can operate through non-ferrous materials such as wood, plastic or aluminum and excellent for switching microcontroller logic level loads. This makes it good for applications like position and limit sensing, security system switch, linear actuators, door switch, and others.



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