DIY ESP32 Wearable: DRM Watch 3 (Suitable for Daily Use)

DRM Watch 3 is my self-made wristwatch based on a Sharp Memory LCD display, ESP32-S2 and the desire to wear it on my hand :)

This is NOT a "Smart watch" ! This device in its functionality is close to a regular electronic watch, with several additional features, and you can add them, reprogram the watch to suit yourself.

Currently, the firmware has all the features inherent in a typical watch and allows you to fully use it on a daily basis.

Watch parts cost about $70 in total.

Features of the watch

• Works stably and is suitable for daily use;
• Fully open source;
• The display always shows the time;
• The battery lasts for more than 14 days, there is a charge indicator;
• Multiple customizable watch faces;
• There is a flashlight, bright white and night red;
• Stopwatch, Timer, works in the background;
• Alarm clocks, up to 10 pcs with names;
• Calendar;
• USB charging, including from TypeC-TypeC;
• Two languages UI: English and Ukrainian.
• The watch has a built-in "flash drive" of 1.2 MB, in which you can throw files
• The clock can open monochrome BMP, Wav files, text TXT documents
• There is a very dim but very pleasant night illumination of the display;
• Convenient menus from which you can access all functions;
• Availability of Wi-Fi, you can save up to 8 networks in memory;
• Ability to synchronize time via Wi-Fi;
• Lots of tunes. You can either just listen to them or set them as an alarm clock.
• Imitation of the sound of kittens meowing;
• You can add a calendar, hourglass, date, and an interesting background to the watchfaces
• Full screen cellular automata and animations (Life, Ant, Fire, Noise, Lava, Ant, Dots)
• You can update the firmware via USB without disassembling the watch.
• Components for assembly are easy to get;
• The case is suitable for standard 22mm straps;
• It is convenient and simple to modify. You can write your own firmware.
• The watch can be used as a field for experiments with ESP32-S2: battery, 3 buttons, beeper, display, 3 LEDs;
• UART log: a tool for developers, displays all bytes received via UART.
• The "About Watch" screen contains information about the developer and firmware version.

Precautions during use:

• The watch cannot be wet. Water protection is almost non-existent here and it will lead to the breakdown of the watch. Light rain or sweat won't do anything to him, but pouring it when washing your hands can be a problem.
• The watch is weakly protected from shocks. The display is not protected, the frames are thin, the body is thin, the watch is designed without a large reserve of mechanical strength, and it is also quite large. Therefore, it is easy to hit it and it will most likely lead to a broken display. I haven't had any problems with the watch being damaged during my months of use, but I've been quite careful with it.
• The watch should be protected from the influence of static. There is a small chance of killing the watch if you quickly remove the sweater) Therefore, either remove the sweater slowly, or remove the watch before doing so, or use a sweater that does not electrify. A particularly risky moment is the setting for charging, here it can slip right through the controller. I advise you to touch the metal part of the charger case before inserting the charging cable - that way you will discharge through the case and not through the watch and everything will be fine.

Tools and Parts

Tools:

• Soldering iron
• SMD Rework station or Soldering hot plate
• Soldering flux
• Soldering wire
• Tweezers
• Screwdrivers
• Scissors
• Scalpel
• Thin wires
• Microscope (recommended)

Parts:

• Board
• Display
• Cut EL backlight
• Components to solder on board
• Battery
• 3d printed back part
• Machined alluminium front part
• Screws

Board

Use gerber files to order board. I ordered on JLCPCB.

Download GERBER here or in project info.

There's also BOM included.

Parts

List of parts needed for assembly.

Links are added for reference, but you can get parts everywhere else, using full name and photo.

• Display Sharp LS027B7DH01A

https://www.aliexpress.us/item/1005005611440829.html

• Connector FPC 10pin 0.5mm pitch

https://www.aliexpress.us/item/10000348360254.html

• Battery lipo 502535

https://ampul.eu/de/batterie/4242-li-pol-akku-450mah-37v-502535

• Buzzer SMD 7525-3.6V-passive

https://www.aliexpress.us/item/1005003620083880.html

• Mosfet 2N7002LT1G

https://www.aliexpress.us/item/1005003079655220.html

• Esp32 board: Lolin S2 Mini

https://www.aliexpress.us/item/1005004438665554.html

• TP4056 Charging module

https://www.aliexpress.com/item/1005006310424899.html

• Resistor set SMD 0603

https://www.aliexpress.us/item/1005002364437129.html

• Capacitors set SMD 0603

https://www.aliexpress.us/item/1005006124283234.html

• RTC Module based on Analog Devices DS3231

https://www.aliexpress.us/item/32822420722.html

• 020 SMD Side View LED White 6000K

https://www.aliexpress.us/item/32419907074.html

• Buttons 2*4*3.5mm Micro SMD Tact Switch Side Button

https://www.aliexpress.us/item/1005004312046546.html

• Screw places SMTSO Surface Mount Copper Nut M1.4X3X1.5-2X0.8

https://www.aliexpress.com/item/1005005579653583.html

• Screws PH000, M1.4, 3mm length

https://www.aliexpress.com/item/1005002364568213.html

• Self tapping screws M1.5, 6mm

https://www.aliexpress.com/item/1005002324715062.html

• Watch band, 22mm

https://www.aliexpress.us/item/1005005890436737.html

• USB Type C cover

https://www.aliexpress.com/item/4000148621089.html

• EL Panel driver: Microchip HV857MG MSOP8 (optional, only if you want backlight)

https://www.aliexpress.us/item/1005005512523052.html

• EL Driver Capacitor SMD 1206 10NF X7R 200V (optional, only if you want backlight)

https://www.aliexpress.us/item/1005004628006766.html

• EL Driver Capacitors SMD 1206 320PCS 16Value (optional, only if you want backlight)

https://www.aliexpress.us/item/1005006124283234.html

• EL Driver Diode ES1D (optional, only if you want backlight)

https://www.aliexpress.us/item/1005005254835443.html

• EL Driver SMD Inductor 1210 3225 22UH (optional, only if you want backlight)

https://www.aliexpress.us/item/32981310345.html

• Glue to connect EL panel MECHANIC MCN-DJ002 Conductive Adhesive Glue Silver (optional, only if you want backlight)

https://www.aliexpress.us/item/1005002369819447.html

Machined Front Panel

The best looking front panel is CNC machined. You can order CNC machining using STEP files included.

If you don't want to order CNC machining, you can 3D print this panel, result is still very good.

Back Panel Parts

Any plastic. I used PLA.

Print back part - any color you want, I used black.

Buttons part - transparent color to make flashlight visible.

Board Assembly Process

Solder all parts according to its places. You can follow pdf soldering plan, or download KiCad project here.

There's a lot of micro soldering.

Also add 24mm wire to ANT testpoint. It works as Wi-Fi antenna (really bad antenna but it works).

You also can order PCBA service to get assembled board using BOM and GERBER files.

Optional testing semi-assembled watch: after soldering resistors, capacitors, USB connector, buttons, voltage regulator, ESP32 chip and quarts. Battery not connected. Short jumper on up-left corner of board (it will bypass charger to let ESP be powered from USB). Hold UP button and connect USB. Device should be recognized. You can flash it with flasher. Press reset button - watch should start. Don't forget to remove jumper before soldering battery!

After assembly i'd recommend cover components side of board with B7000 glue to cover all the contacts. This will protect this side from water and moist.

After assembly i'd recommend cover empty side of board with captone tape. This will protect this side from water and moist.

Flash firmware

To make assembly process as easy as possible, I made flasher to flash board by one button.

Here you can download flasher (download any version you want)

Here's how to use it

1) Open flasher

2) Connect USB cable to board

3) Hold "Up" button

4) Press "Reset" button

5) Release "Up" button

6) Press "Прошити годинник" (flash watch)

7) Wait while flashing complete

8) Disconnect watch

9) Press "Reset" button.

Watch should start now.

Firmware update process is the same, user data will not be deleted.

EL Backlight

The electroluminescent panel (EL panel) is an integral part of the lighting system. This is a panel that glows under the influence of high voltage and frequency. They are also called light-emitting capacitors (LECs). These are just interesting facts to better understand what it is.

The trick of this type of backlight is that the panel is very thin, shines very uniformly in a pleasant blue color, and it can also be cut into pieces of the desired shape. But after cutting, the task of connecting to the panel is difficult. I used single core wires and conductive glue for the connection.

Cons: being located behind the display used here, it is barely visible, but it is enough at night. It also squeaks a little while working. And for its operation, a rather complex driver scheme is required.

I advise you to buy the blue color, because the EL panel is naturally of this color, and it is stupidly painted in other colors, and the paint absorbs part of the light. If a painted panel has arrived, it can be cleaned of paint with a blade.

In dark night you will be able to see big clock.

EL panels is cuttable, and on its edge is located 2 electrodes - outer and inner.

1) Cut panel in pieces which fits screen size

2) Use very sharp knife to gently cut back side of EL panel lamination. Make 2 cuts (over outer and over inner electrode)

3) Push thin wire under lamination to somehow contact the electrode.

4) Add condictive glue to make better contact.

5) Place thin wires for comfortable connection to EL1 and EL2

6) Add captone tape to back side of EL panel to protect thin wires.

7) Solder EL1 and EL2 to panel. Polarity doesn't matter.

8) Check if it works.

9) Fix EL panel on board with small pieces of scotch tape to prevent damaging this wires.

Engrave Back and Front Panels

If you have laser engraver, you can engrave back panel.

I used 4W 365nm laser with my DIY engraver to engrave.

Assembly

When all parts are tested and works, it's time to assemble watch.

At first connect LCD, then isert buttons in back panel, then screw back panel to board, then screw front panel to back panel.

Pay attention to LCD+Backlight thickness! If frame is pressing too hard on the display, it can brake instantly or start degrade slowly over time.

Set Languare and Sync Time

To set language to English follow this:

1) Menu

2) "Налаштування"

3) "Дисплей"

4) "Мова"

Press once and language english set.

Then go to wifi settings, add your wifi network.

Then go to time settings and run auto sync.

Then go to timezone settings and adjust timezone to yours.

Now watch should be ready to use!

Calibrate Battery

To make watch measure battery level as good as possible, I made calibration procedure.

It takes much time, but it improves battery indication a lot.

Fully charge watch. Go to settings-display-battery calibration. Start calibration.

It will take 5-10 hours. Watch will not respond for any buttons. Do not touch watch until it fully discharges.

After watch is turned off, calibration is complete. Charge it. After this watch can be used and you will see most accurate battery level indication.