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.

Breadboarding

Carefully place the Dragon Tail breakout into the breadboard as shown. Pay special attention that the 3V pins are aligned with the left side power rail.

Use jumper wires and the components to build the circuit as shown in the circuit diagram above and the photos here.

You can use two male/male jumper wires to extend and connect the solenoid cable to the board.

NOTE: We're using the right side power rail for the 6V 4xAA battery pack and must connect only the black ground rails. DO NOT connect the right side red rail's +6V to the left side's +3V red rail!

Attach Solenoid

One tricky part of this type of build can be how to mount the solenoid to strike the bowl or gong. We're going to use the weight of the battery pack to hold it in place, and it's height for positioning.

Use double-stick foam tape to attach the solenoid to the battery pack as shown. You will want to check the height against the singing bowl for height positioning.

Add CLUE

If you haven't already, plug the CLUE into the Dragon Tail.

Breadboard Mount

Breadboards come with double-stick foam tape already attached to their bottoms. We'll use this to attach the breadboard and the rest of the circuit/CLUE to the battery case as shown.

Remove the protective backing and align the board with the battery pack so they can stand freely, then press and hold them together for ten seconds or so to allow the adhesive to set.

Add Feet

Add the four rubber bumper feet to the bottom as shown. This will give the device some needed friction to prevent it from moving when the solenoid strikes the bowl.

CLUE Power

The 3x AAA battery pack will power the CLUE itself (the 4x AA being used only for the solenoid). Adhere it to the breadboard's double-stick foam tap as shown and then plug it into the JST battery connector on the CLUE.

We'll use the on/off switches on the battery cases to turn on and off the entire device.

Next we'll code the CLUE in CircuitPython.

This guide was first published on May 20, 2020. It was last updated on May 20, 2020.

This page (Assemble the Pose Chime) was last updated on Oct 30, 2020.