Have you ever wondered how a speedometer works? In this tutorial, we will show you how to build your own speedometer by measuring the magnetic pulses generated by a disc magnet located on a spinning wheel.SOFTWARE:Step 1: Connections
Step 2: Software
- Connect the Wireling TinyShield to the TinyScreen+ using the tan connectors.
- Use the long 5-pin Wireling cable to connect the Hall-Effect Sensor to Port 0 on the Wireling TinyShield.
- Connect the TinyScreen+ to your computer via the micro USB cable.
- Open your Arduino IDE and select the TinyScreen+ from Tools -> Board.
Step 3: The Code
- Confirm that you are connected to the correct port. Navigate to Tools -> Port and select the port that contains “TinyScreen+.” The port number may vary.
Step 4: Hardware
- Please download the code and required dependencies from the above Software section.
- Note that you will most likely need to modify some of the constant parameters located at the beginning of the program:
- The constant Boolean value USE_MPH allows you to choose between the English and metric systems for both the WHEEL_DIAMETER input and the speed output.
- Make sure that you set the WHEEL_DIAMETER parameter as it is essential to produce accurate results. Unlike store-bought speedometers made for a range of wheel sizes, you will be able to specify an exact value.
- RPM_SAMPLE_PERIOD allows you to control how far into the past the program includes sensor readings. Feel free to experiment with how this value impacts your results.
- Once you have modified these parameters, upload the code to the TinyScreen+ using the upload button on the top left corner of the Arduino IDE interface. (pictured below)
- In order to measure the speed, it is necessary to place the disc magnet somewhere on a rotating wheel. On bicycles, a common location is on the spokes. We attached ours on a screw protruding from the wheel of a scooter. If there are no magnetic surfaces, you may need to tape or glue the magnet in place. Do not place the disc magnet on a rim if you have brake pads.
- The Hall Sensor needs to be placed somewhere on the frame of the vehicle. Make sure to mount the sensor in such a way that the magnet will come very close to the front with every rotation. A strong magnet will enable distances of 5-6 inches, while a weak magnet may need to be within 2 inches or less.
- Mount the TinyScreen+ wherever you prefer the viewing angle.
That’s all there is to it! We hope you enjoyed this simple speedometer project!