This tutorial will (hopefully) give you everything you need to build your own wearable, wireless velocity measurement device. There are three main tasks that need to be completed:
Build the device
Load the software onto the device
Connect the device to your phone or tablet
My intention is to make these instructions as simple as possible and you shouldn't need any special skills or knowledge to complete this project.
This project is based upon the Arduino electronics platform. If you want to learn more about Arduino, you can watch this TED talk (watching the talk is not necessary in order to follow these instructions).
This is a very simple Arduino project. We will use a small Arduino with built in Bluetooth capability to control one additional component that provides our velocity measurements. Finally, we need a power supply for the system.
A microcontroller (Arduino Nano 33 BLE)
An inertial measurement unit (BNO055 or BNO08x Breakout Board): This component includes an accelerometer, gyroscope and magnetometer. More importantly it includes a BNO chip made by Bosch which will interpret the sensor readings for us. This means that we can rely on the mathematical prowess of the Bosch engineers to give us a very stable calculation of velocity. Unfortunately, at the time of writing, the availability of these boards was unpredictable - you should be able to find an appropriate component, but there are various different types. You can find these components from electronics distributors (Mouser, Digi-Key, RobotShop), Amazon or on ebay. Note that as far as I can tell, the difference between premium and budget versions (my categories) seems to be ease of use. The budget versions often require additional connections to be made.
You will also need:
A soldering iron
Headers - but you will get these with the Arduino
A small container for the electronic components
Essentially we just need to make four connections between our Arduino and our BNO Breakout Board:
Bring power to our breakout board from the Arduino (red connecting line in the figure below). To do this we connect the hole labelled 3V3 on the Arduino to the voltage input on our breakout board (normally labelled VCC or VIN);
Connect the Arduino's ground (GND) to that of the breakout board (black connecting line);
Connect the SDA line of the Arduino (this is hole A4) to the SDA line on the breakout board (blue connecting line);
Connect the SCL line of the Arduino (hole A5) to the SCL line on the breakout board (yellow connecting line).
I have found the following approach to be pretty easy and result in a neat and compact system.
Onboard Software (Firmware)
Receiver Software (Phone or Tablet Application)
Once you have downloaded the Blexar App, open it up. You should be greeted with a menu like the one in the image, which lists the Bluetooth devices in your phone or tablet's vicinity. Look for the device named 'Arduino' or 'Velocity', and select it.