Tamagotchi Health Companion
A friendly step-counter!
Embedded Files
Overview:
The Tamagotchi Health Companion is a pedometer in the style of the Tamagotchi Pet, a cute Japanese toy. The goal is to help users stay healthy and feel a sense of companionship.
Tamagotchi, released by Bandai on November 23, 1996
Description:
Our Tamagotchi uses an accelerometer to count steps, and once the user has reached a milestone (such as 5,000), we aimed for the display to change to celebrate this and for the character evolves. We also included four user-facing buttons to code mini games and interact with the display.
Board Components & Features:
An ESP32 as our compute to run the display and process accelerometer & button inputs
A 3000 mAh battery and related battery charger IC to charge the battery, which lasts a full day.
An accelerometer with internal gyroscope, intended to tick once the board reaches a certain angle (and thus count steps)
A transflective display (with a lower power usage) that shows step counts, displays game interfaces, and shows cute animations to make the Tamagotchi lively
Buttons used to interact with the board. 4 are front facing for the user to interact with and two are boot/reset for firmware
A switch to toggle between charge mode and plug-in power mode
A micro-usb port for charging
Miscellaneous diodes, fuses, and voltage regulators
Schematic & Design Choices
Schematic:
Micro USB
The Micro-USB charge circuit, that includes fuse and schottky diode for safety.
Charge Battery
The battery charging IC, which makes sure that the battery charges to its maximum voltage.
LDO - 3.7 to 3.3 V
An LDO that converts the 3.7V from the battery to the 3.3V required for the display. This also supplies power to the ESP-32.
Display
The display, which interfaces with the ESP-32.
Accelerometer
The accelerometer, which also communicates with the ESP-32. This one had no pins sticking out, and was thus more difficult to solder. Hence, we added a ball-switch we could optionally solder in.
Ball-Switch
The ball-switch. This was chosen as a back-up option for the accelerometer, as it is both easier to solder and easier to write code for. We chose one that activates a smaller angle, as the Tamagotchi would likely be in a persons pocket and needs to be more sensitive to trigger a step.
ESP-32
The ESP-32, which is connected to the boot and reset buttons.
Buttons
The 4 user-facing buttons.
+ 6 test points (for bring-up)
Layout & Design Choices
Our General Layout Principles:
Making power traces thicker
Blocking together active components and passives that belong together
Putting interactive components in logical places. The 4 user-interactable buttons, for example, are placed below the display. The micro-usb is also on the edge of the PCB (though we accidentally assigned a mini-usb footprint to it, as will be discussed later during the bring-up process). We also chose the ball-switch location to be have the largest range of motion, so it tracked steps more accurately.
Bill of Materials (BOM)
Price per board: $52.49
Bring-up Progress:
Note: The first board was severely burnt and was no longer viable, so we created a second board.
This is the board at the halfway soldering point. There was discoloration around the accelerometer due to using the heat plate to solder it on.
This is the board when it was fully soldered. There is a lot of burnt flux on the top, and the USB-micro was too inset because of the component-footprint mismatch.
The back was also severely burnt, and there is melted plastic all along the bottom. Near the top of the board, there was also exposed copper ground pour.
The second board was fully functional (replaced accelerometer with tilt switch).
This is the board at the halfway soldering point. We have some components left to solder, such as the ball switch.
The back-side of the board after we finished soldering (missing a button in this photo, which was soldered later).
This is the board once it was put in its package. There was a spot for the battery to slot in to reduce unnecessary movement.
Completed Project:
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