While practicing Yoga on your own, it can be helpful to use an interval timer to let you know when you have completed a certain pose. While there are myriad apps that offer this functionality that play a sound when the time is right, there is something wonderful about the sound of a physical gong being struck.

This project uses a CLUE board to display poses, proximity control to start your pose timer with the wave of a hand, and a solenoid striker to chime a singing bowl.

Parts

The Yoga Pose Chime uses the CLUE to keep track of time spent in a pose, and to trigger the solenoid to ring the pleasant chime when it is complete. The solenoid draws more current at a higher voltage than the CLUE is meant to provide directly, so we'll create a transistor-based circuit to drive the solenoid.

The way the driver circuit works is that a small signal current tells the transistor to open up the flow of a larger current. When it's time to chime, the CLUE will send a 3V signal over pin 2 to the transistor, which opens the floodgate of the full 6V of the four AA batteries, at the much higher amperage needed to drive the solenoid.

For much more info on transistors, check out this excellent guide, Transistors 101.

Next we'll code the CLUE in CircuitPython.

Text Editor

Adafruit recommends using the Mu editor for editing your CircuitPython code. You can get more info in this guide.

Alternatively, you can use any text editor that saves files.

Installing Project Code

To use with CircuitPython, you need to first install a few libraries, into the lib folder on your CIRCUITPY drive. Then you need to update code.py with the example script.

Thankfully, we can do this in one go. In the example below, click the Download Project Bundle button below to download the necessary libraries and the code.py file in a zip file. Extract the contents of the zip file, open the directory Yoga_Pose_Chime/ and then click on the directory that matches the version of CircuitPython you're using and copy the contents of that directory to your CIRCUITPY drive.

Your CIRCUITPY drive should now look similar to the following image:

How to use the Yoga Pose Chime

• Turn on both battery packs first, so the CLUE turns on and the solenoid can be triggered
• You'll begin the first pose timer by waving your hand close to the CLUE's proximity sensor which is mounted right above the screen
• The solenoid triggers once to chime the bowl, signaling the pose can begin
• After 30 seconds (or your chosen interval time) the solenoid will chime twice, signaling the end of the pose
• You can press the B button on the CLUE to skip ahead to a different pose, the A button to go back to a pose