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Augusto Marinucci’s Solid State Tank is a custom e-paper wristwatch with the rectangular profile of a Cartier Tank and an unusually low-power design. Its display is made from donor e-paper material cut to fit a custom PCB—not a standard watch module—and its reported battery-life figure is theoretical rather than a proven service interval. The project is a useful design reference, but published coverage does not provide a complete, verified recipe for reproducing its display.
What the Solid State Tank is
The Solid State Tank combines a clear, 3D-printed case with a custom digital display, drawing inspiration from both the Cartier Tank’s rectangular dress-watch styling and CW&T’s Solid State Watch. Marinucci described the concept to Hackster.io as “a clear case tank style watch with a DIY [ePaper] screen to be potted in clear epoxy.”
The central maker challenge is the display. Rather than fitting a ready-made watch screen into a case, the design adapts donor e-paper material to a custom board and connects its common electrode with conductive adhesive. That makes the project more distinctive than a conventional microcontroller-and-display build, but also harder to reproduce from the available public descriptions.
How the display and electronics are arranged
Custom display board
Hackaday’s January 26, 2024 account describes display segments formed in the top copper layer of a four-layer PCB. Filled and capped vias connect those segments from the lower layers. Donor e-paper is cut to shape with scissors, then glued around its edge to establish the common-electrode connection. Low-profile board-to-board connectors join the display board to the control PCB.
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- This is a programmed watch. Built on the ESP32 core, this device offers open hardware/software designs for endless customization. Program with MicroPython, or ESP-IDF, and integrate external modules like sensors to create tailored solutions.
- A crisp 200x200 monochrome screen ensures visibility in direct sunlight. Dynamic refresh technology minimizes energy use, consuming power only during content updates.
- Equipped with a tri-axis motion sensor and haptic feedback for gesture controls. Exposed GPIO ports allow seamless integration of add-ons (e.g., environmental or biometric sensors).
- Achieve 5-7 days of operation in low-refresh mode. Customizable sleep cycles and motion-triggered activation balance performance and longevity.
- Access open-source 3D case designs for personalized enclosures. Join a global community sharing watch faces, plugins, and firmware tweaks for limitless innovation.
The report gives the broad construction idea, not a complete fabrication recipe. It does not identify the donor panel model or publish a verified assembly sequence. Marinucci reportedly said the project was reproducible and that smaller screens are easier to clamp, but that does not establish that arbitrary retail e-paper panels can be cut safely. In particular, the coverage should not be read as a general instruction to trim an ordinary e-paper module.
Control board and power path
The reported control electronics comprise a PIC16 microcontroller, a Micro Crystal RV-3028-C7 real-time clock, a MAX1722 boost converter, two logic-controlled load switches and a CR1616 cell. The converter raises the cell supply to 5 V for the design.
Rank #2
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Hackster.io’s account explains the sleep strategy: one load switch is tied to an RTC clock output configured to provide a 1 Hz clock each minute; the other is controlled by the microcontroller and keeps the supply on for as long as required. The intent is to let the MCU remain off for most of the time instead of continuously consuming power. Marinucci summarized the approach as using “two load switches in parallel to keep the MCU [Microcontroller Unit] in the off state for most of the time.”
Hackaday reports 45 nA as the RTC’s consumption. That is a component figure, not the total watch’s average draw. The same report cautions that small button cells can be overstressed, which may damage the cell and reduce runtime.
Rank #3
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What the battery-life number means
Hackster.io reported Marinucci’s average power draw as 495 nA and calculated an ideal 11.5-year lifetime from a 50 mAh battery. The 11.5-year figure is a calculation, not a demonstrated period of use. Hackster notes that temperature variation and current peaks reduce real-world life; the separate button-cell warning also matters when interpreting a design that draws brief loads from a small cell.
No independent replication or field measurement of this watch’s battery life is established in the available reports. Treat 495 nA as the designer’s reported average and 11.5 years as an ideal estimate under the stated battery-capacity assumption, not a promise for a finished build.
Rank #4
- This is a programmed watch. Built on the ESP32 core, Watch V2.0 PLUS combines open-source hardware and software for limitless customization. Developers can program with MicroPython, or ESP-IDF, while users personalize designs with 3D-printed cases and straps.
- A 200x200 monochrome screen delivers sharp visibility even in direct sunlight. Dynamic refresh technology ensures ultra-low power consumption, updating content without draining energy between changes.
- Seamlessly sync with external APIs (weather, news, music) and devices through multi-protocol support. Built-in 3-axis accelerometer enables gesture controls, while real-time clock (RTC) ensures precise timekeeping with alarms and calendar functions.
- Onboard USB-to-serial adapter allows instant programming. Expand functionality via GPIO pins for adding sensors or peripherals, backed by a thriving global maker community sharing templates and watch faces.
- Achieve 5-7 days of operation in time-only mode or 2-3 days with active data updates. Customizable sleep modes and motion-triggered wake-ups extend usage while balancing performance.
Case sealing and the serviceability trade-off
The case was modeled and 3D-printed, then the assembled watch was potted in UV-cured resin. Hackster describes the result as waterproof and robust, but its account also says the battery is not replaceable. The resin-sealed construction therefore trades access for enclosure protection; the reports do not establish a repair or battery-replacement procedure.
Can you build one from the published information?
The coverage is enough to understand the architecture, but not enough to follow as a complete build guide. It describes the PCB approach, donor display material, adhesive connection, control components and enclosure treatment, while leaving key reproducibility details unspecified.
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Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEScan for outdated or missing drivers - takes under a minuteDriver Scan →- Documented at a high level: the four-layer display-board concept, cut donor e-paper, conductive adhesive at the common electrode, board-to-board connection, named control components and resin potting.
- Not established in the reports: the exact donor display, complete bill of materials, full fabrication files and a verified step-by-step assembly procedure.
- Practical implication: treat this as an engineering reference unless you have the original project’s full technical materials. A small e-paper display module may help prototype layouts, but it is not a confirmed drop-in substitute for the custom display.
How it differs from other e-paper watch projects
LightInk and Watchy are useful points of comparison, but neither is the Solid State Tank or a source for its component list.
| Project | Display and fabrication | Electronics and power approach | What the documentation supports | Serviceability or enclosure details |
|---|---|---|---|---|
| Solid State Tank | Donor e-paper cut to shape and attached to a custom segmented PCB; exact panel model not stated (Hackaday, Jan. 26, 2024). | PIC16, RV-3028-C7 RTC, MAX1722 boost converter, two load switches and CR1616 cell, as reported by Hackaday and Hackster.io. | Broad construction approach reported; complete fabrication recipe and verified assembly sequence not stated. | UV-resin-potted, described as waterproof; battery not replaceable (Hackster.io). |
| LightInk | Separate ESP32-based e-paper watch; its documentation covers PCB, case, display placement, solar-cell mounting and tactile buttons. | Solar-power ambitions; its author describes reducing ESP32 boot overhead with an RTC-memory wakeup stub. | Build instructions cover more of the assembly process than the Solid State Tank reports do. | Battery serviceability and sealing details not stated in the cited LightInk material. |
| Watchy | Ready-made 1.54-inch, 200×200 SPI e-paper display. | ESP32-PICO-D4, accelerometer, RTC, vibration motor, buttons and 200 mAh lithium battery; graphics use GxEPD2 and the Arduino ecosystem. | Hardware overview provides a reference for an off-the-shelf display-oriented watch platform. | Battery replacement and enclosure sealing details not stated in the cited hardware overview. |
LightInk’s reported boot-power issue and wakeup technique belong to that project, not Marinucci’s watch. Likewise, Watchy’s display and battery are not specifications for the Solid State Tank.
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