Following the circuit diagram, stitch conductive traces between all four connections to the UV index sensor (3V, SDA, SCL, and GND). Use the same technique as with the piezo, leaving tails on your knots at each end of all four threads.

Apply nail polish to all eight knots, wiping the brush on the edge of the bottle opening first to remove all but the smallest amount. Remember, less is more! Just saturate the knot, not the connection to the FLORA or sensor board. Allow to dry, then tug test before snipping the thread tails short.

Follow the instructions on the UV index guide for testing your sensor-- upload the demo code and verify with the serial monitor that the sensor is returning readings.

Reattach the hat's ribbon using plain thread, securing the battery in the process.