Introduction: Multifunctional Watch With Circuit Playground Express (CPX) and Servo Motor

In an introduction to engineering class at Endicott College, we were tasked to make something with our Circuit Playground Express (CPX) and Servo Motor that provide three functions for the user. Simple enough we came up with the idea of a simple watch with minor functions compared to a more meticulous watch you'd see from a major retailer. The three functions we compiled were a nearly exact one-minute timer displayed by a hand connected to our Servo Motor, a light-up display custom--depending on how long the code is set--length timer, and a rainbow light-up display when the CPX is shaken representing physical activity.

Supplies

*All prices are listed as of November 8, 2023

Step 1: 3D Print Your Watch Base and Band

We have a link supplied with the parts we used to assemble our watch:

Watch blueprint

Attachments

Step 2: Making and Downloading Code

Just like the 3D print we supplied the code for ease of access which will direct you to Adafruit.

Block Code: Watch Code

But, for those who are curious, the function on the top left is to set the main color when the CPX is powered to blue signifying power to the device.

Unanimous with being powered up, the function just below that to the left is for the servo motor which will cause the motor with a hand attached to rotate once every minute.

The function in the middle is the physical activity reminder function. When you shake the function the rainbow animation will play for about 5 seconds as it says 5000ms.

The third main function is the timer function. In case you wanted to plan an alarm, you could copy and paste each grouping of the supplied pixel rotation which signifies one-second passing. You can take out or add in as many of those bricks as you want for your alarm. This function will not interfere with the rainbow function as the white pixel will bleed through the code and not make that much of a difference.


For those wanting the best, here's our Python code download along with the video on how to download the block code.

Attachments

Step 3: Assembly

For assembly, you should focus on working on connecting the links first so you can figure out how many you need to fit someone's wrist. Then once you figure it out lay your watch out flat and prepare to lay in your equipment.

First, you're going to want to plug your charged battery into the CPX and the CPX should be up and running (if not then you either did not upload your code correctly or you did not reset your CPX before downloading or your CPX is defective).

Next, clip your alligator clips into the correct spots on the CPX and orient your wires for the servo motor to where they aren't very bunched or tugging on one another. Once you get them out let them out of the top center of the base and let them hang.

Grab your numeric cover with the servo motor attached to it seal (glue or tape) to the base and attach your wires to the correct holes on the servo motor wire.

By now your watch should be assembled and you should be able to wear it and use all the functions and show off to all your friends.