6 layers69.7 × 76.7 mm
Amulet controller
EPFLXplore/XRE_LeggedRobot_HW
PCB designs for Xplore Research's robot dog project
414 parts348Apache-2.0
4 layers29 × 29 mm
Water timer revB
atelierlelu/water-timerA small battery-powered reminder to water a plant.
- Size
- 29 × 29 mm
- Copper layers
- 4
- Thickness
- 1.61 mm
- Parts
- 30
- Nets
- 24
- Pads
- 88
- Tracks, vias
- 180, 33
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 3 Oct 2026
- Updated
- 3 Oct 2026
Overview
Water timer revB is an open-source printed circuit board by atelierlelu, from the atelierlelu/water-timer repository on GitHub. It is a 4-layer board of 29 × 29 mm with 30 parts on 24 nets, routed with 180 tracks and 33 vias.
It is built around the S2B-PH-SM4-TB. Its parts include 7 resistors, 6 capacitors, 5 diodes, 2 connectors and 2 switches. It belongs with the STM32 boards of this library.
Main components
1README
README.mdWater timer
CC-BY-4.0. Copyright (c) 2026 Atelier Lelu.
A small device to remind you to water a plant. Battery powered but it lasts years. That's it.
An article about the project is at https://lelu.uk/water-timer/.
How to use
Once assembled, enter setup mode to configure how often it waits before blinks (1, 3 or 7 days) by long pressing the top right button for 1.5 seconds. When you release you can cycle through durations by pressing the centre button - green LEDs will blink once (for 1 day), 3 times (for 3 days) or a long blink for 7 days. It auto saves after 10 seconds. Once the 1/3/7 days have passed, the device will blink green every minute (twice) to remind you to water the plant. Once watered press the centre button once, green LEDs flash as acknowledgement and that's it. When the battery is low the red light will flash on button presses of when watering is due - but it should take years before you reach that point.
In this repository
| Path | What it is |
|---|---|
enclosure/print/ | STLs to print: back, front, light mask, hook |
enclosure/source/ | Matching STEP files, for editing |
hardware/ | KiCad project, plus the JLCPCB gerbers, BOM and placement file. The schematic is hardware/schematic.pdf |
firmware/ | Plant-timer firmware, flash and test tools |
docs/ | Documentation |
Make one
Print the four STLs, order the board, solder the coin-cell holder, flash the firmware, then close the case. The steps, including which jumper to close for a cell-powered timer, are in docs/build.md.
Flash before the board goes into the case. From firmware/:
make
make flashLeave the option bytes alone. Programmer wiring and the button and LED behaviour are in firmware/README.md.
Assembly, in order: hook, cell, board on the alignment pins, light mask, front. There are no screws. The picture is docs/exploded.png.
License
Three licenses, one per kind of file. See LICENSE.md. Hardware is CERN-OHL-P-2.0, firmware is MIT, and the documents are CC-BY-4.0. The ST files under firmware/Drivers/ stay BSD-3-Clause.
Parts
30| Qty | Value | Footprint | References |
|---|---|---|---|
| 5 | 0.1u | Capacitor_SMD:C_0402_1005Metric | C1, C2, C4, C5, C6 |
| 5 | 10k | wamde:R_0402_1005Metric | R3, R4, R5, R6, R7 |
| 2 | 10k | Resistor_SMD:R_0402_1005Metric | R1, R2 |
| 2 | D_Schottky | Diode_SMD:D_SOD-123 | D4, D5 |
| 2 | Green | LED_SMD:LED_0805_2012Metric | D1, D2 |
| 2 | MountingHole | MountingHole:MountingHole_2.5mm | H1, H2 |
| 2 | SW_Push | wamde:TS-1187A-B-A-B SPST switch | SW1, SW2 |
| 2 | SolderJumper_2_Open | Jumper:SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm | JP1, JP2 |
| 2 | TestPoint | TestPoint:TestPoint_Pad_D2.0mm | TP8, TP11 |
| 1 | 10u | Capacitor_SMD:C_0402_1005Metric | C3 |
| 1 | Conn_02x04_Top_Bottom | wamde:SOIC_clipProgSmall | J2 |
| 1 | LOGO | LOGO | G*** |
| 1 | Red | LED_SMD:LED_0805_2012Metric | D3 |
| 1 | S2B-PH-SM4-TB | wamde:BAT-TH_MY-2032-22 | P1 |
| 1 | STM32L011F4Px | Package_SO:TSSOP-20_4.4x6.5mm_P0.65mm | U1 |
Questions
How big is the Water timer revB PCB?
It measures 29 × 29 mm and has 4 copper layers, 1.61 mm thick.
What parts does the Water timer revB use?
30 parts, built around the S2B-PH-SM4-TB. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Water timer revB KiCad files?
From the atelierlelu/water-timer repository on GitHub, at the commit this page was made from: the board is hardware/water_timer_revB.kicad_pcb and its schematic hardware/water_timer_revB.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Water timer revB design in my own project?
Its repository states no licence, so its author keeps all rights: ask atelierlelu before reusing the design.
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