2 layers105 × 90 mm
Low Power Desktop Weather Station
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65 parts4
2 layers56 × 56 mm
Pps watch
idlehandsdev/pps-watch42An extremely accurate watch that doesn't tell time.
- Size
- 56 × 56 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 39
- Nets
- 32
- Pads
- 117
- Tracks, vias
- 196, 118
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 30 Jun 2026
- Updated
- 5 Jul 2026
Overview
Pps watch is an open-source printed circuit board by idlehandsdev, from the idlehandsdev/pps-watch repository on GitHub, published under the AGPL-3.0 licence. It is a 2-layer board of 56 × 56 mm with 39 parts on 32 nets, routed with 196 tracks and 118 vias.
It is built around the 74HC125D, 74AHC1G86SE and MAX-M10S, with the BU2450SM-JJ-GTR, CONSMA002-SMD-G-T and PESD0402-140 among its other parts. Its parts include 8 resistors, 5 capacitors, 4 ICs, 4 diodes and 4 connectors. It belongs with the wearables boards of this library.
Main components
6
74HC125D
SO-14-40℃~+125℃ 1 11ns@4.5V,50pF 160uA 2V~6V 4 7.8mA 7.8mA 74HC Tri-State Unidirectional SOIC-14 Buffers, Drivers, Receivers, Transceivers ROHSNexperiaBuffers, Drivers, Receivers, Transceivers
74AHC1G86SE
SOT-353-40℃~+125℃ 1 1.5V~3.85V 1uA 2V~5.5V 500mV~1.65V 74AHC Series 8.8ns@5V,50pF 8mA 8mA XOR Gate SOT-353 Logic Gates ROHSDiodes IncorporatedLogic Gates
MAX-M10S
LCC-18_10.1X9.7LCC-18_10.1X9.7 New Arrivals ROHSu-bloxUncategorisedBU2450SM-JJ-GTR
--40℃~+315℃ - Button And Strip Battery Connector ROHSMPDButton And Strip Battery Connector
CONSMA002-SMD-G-T
SMDSMD Coaxial Connectors (RF) ROHSTE ConnectivityCoaxial Connectors (RF)
PESD0402-140
0402-55℃~+125℃ 0.25pF 10uA 14V 40V Bidirectional ESD IEC 61000-4-2 0402 ESD and Surge Protection (TVS/ESD) ROHSLittelfuseESD And Surge Protection (TVS/ESD)
README
README.mdPPS Watch
The Most Accurate Watch that Doesn't Tell Time.
What it does
- Receives GPS , achieves position/time fix
- Outputs 1PPS (one pulse per second) on the GPS module's hardware TIMEPULSE pin, silent until locked, active at 1Hz once locked
- Distributes that PPS signal across a BNC connector via buffered outputs
- Accepts an external PPS reference, compares it against the GPS PPS via a hardware XOR phase comparator, with LED indicators for PPS presence and phase offset
- No microcontroller. No firmware. The GPS module's hardware PPS pin drives the LEDs and BNC outputs directly through logic buffers.
Hardware
- GPS module: u-blox MAX-M10S
- Antenna: External via SMA, no onboard antenna. Direct-mount stub antennas (Quectel YEGT001AA right-angle / YEGT002AA straight) screw directly onto the SMA connector, no cable
- Buffering: 2x 74HC125 quad buffer (GPS output side, external input side)
- Comparator: 74AHC1G86 single XOR gate
- Indicators: 0805 SMD LEDs -- 1x red (PPS), 2x green (fix / external PPS)
- Power: CR2450 coin cell, switched via SW1, V_BCKP always connected
- Config port: Qwiic (I2C) for one-time setup via u-center if needed
- Connectors: 2x BNC, 1x SMA (antenna), 1x Qwiic
See the schematic for full signal flow and the BOM for part numbers.
CAD
This is a KiCad project. PCB mechanical design and 3D assembly were done in Fusion 360.
Fusion 360 share link: https://a360.co/4xXmWnG
BOM
- ** BOM should be up to date! - https://www.digikey.ca/en/mylists/list/XIH163JVIJ
- ** R2 was a 0R resistor, but the BOM now includes a PTC instead.
| Reference | Qty | Value | Digikey Part No. |
|---|---|---|---|
| AE3 | 1 | YEGT002AA | 2958-YEGT002AA-ND |
| BT2 | 1 | BU2450SM-JJ-G | BU2450SM-JJ-GCT-ND |
| C1 | 1 | 100pF C0G | 311-1111-1-ND |
| C2, C3, C4, C5 | 4 | 0.1uF | 311-4348-1-ND |
| D1 | 1 | LED Red 0805 | 160-1415-1-ND |
| D2 | 1 | PESD0402-140 | PESD0402-140CT-ND |
| D3, D4 | 2 | LED Green 0805 | 475-LGR971-KN-1TR-ND |
| J1, J4 | 2 | BNC 2466267-1 | 17-2466267-1-ND |
| J2 | 1 | CONSMA002-SMD-G-T | 343-CONSMA002-SMD-G-TCT-ND |
| J6 | 1 | Qwiic | 1568-14417-ND |
| L1 | 1 | Ferrite Bead | 490-1040-1-ND |
| R1 | 1 | 470R | 311-470ARCT-ND |
| R2 | 1 | 500mA PolyFuse | F2772CT-ND |
| R3, R6 | 2 | 10K | 311-10KARCT-ND |
| R4, R5 | 2 | 330R | 311-330ARCT-ND |
| SW1 | 1 | Power Switch SPDT | 401-2016-1-ND |
| U1 | 1 | MAX-M10S | 672-MAX-M10S-00BTR-ND |
| U3, U6 | 2 | 74HC125D | 74HC125DCT-ND |
| U5 | 1 | 74AHC1G86 | 296-1094-1-ND |
Watch Assembly
3D Printed Parts
Print the following files from the CAD/ folder:
CAD/pcb_frame_mount.stl-- frame that holds the PCBCAD/watch_band_mount.stl-- mounts the band to the frame
Watch Band
Any standard 22mm watch band works. Tested with:
Bandini Nylon Sports Watch Band Strap 22mm
Hardware
- 2 x M2x6mm Flat Head Plastic Threading Screws to mount body to strap mount. - https://www.mcmaster.com/90485A415/
- 2 x M3x6mm Pan Head Plastic Threading Screws for mounting PCB to Body - https://www.mcmaster.com/99461A939/
- 2 x M3x35mm Round Head Machine Screws to mount strap. Just Thread into the plastic snugly https://www.mcmaster.com/92000A134/
Felix Corp -- Idle Hands Dev R&D Division Asset Tag: FC-IDH-UTC-001
Parts
39| Qty | Value | Footprint | References |
|---|---|---|---|
| 4 | 0.1uF | Capacitor_SMD:C_0805_2012Metric | C2, C3, C4, C5 |
| 3 | 330R | Resistor_SMD:R_0805_2012Metric | R1, R4, R5 |
| 2 | 10K | Resistor_SMD:R_0805_2012Metric | R3, R6 |
| 2 | 2466267-1 | project_footprints:TE_2466267-1 | J1, J4 |
| 2 | 4.7K | Resistor_SMD:R_0805_2012Metric | R7, R8 |
| 2 | 74HC125D | project_footprints:SOIC14_TOS | U3, U6 |
| 2 | LED_G | LED_SMD:LED_0805_2012Metric | D3, D4 |
| 1 | 0R | Resistor_SMD:R_0805_2012Metric | R2 |
| 1 | 100pF C0G | Capacitor_SMD:C_0805_2012Metric | C1 |
| 1 | 74AHC1G86 | Package_TO_SOT_SMD:SOT-23-5 | U5 |
| 1 | BU2450SM-JJ-G | project_footprints:BAT_BU2450SM-JJ-G | BT2 |
| 1 | CONSMA002-SMD-G-T | project_footprints:LINX_CONSMA002-SMD-G-T | J2 |
| 1 | G*** | kibuzzard-6A2251CD | kibuzzard-6A2251CD |
| 1 | G*** | kibuzzard-6A225147 | kibuzzard-6A225147 |
| 1 | G*** | kibuzzard-6A225392 | kibuzzard-6A225392 |
| 1 | G*** | kibuzzard-6A226675 | kibuzzard-6A226675 |
| 1 | G*** | kibuzzard-6A2255A9 | kibuzzard-6A2255A9 |
| 1 | G*** | kibuzzard-6A225EFE | kibuzzard-6A225EFE |
| 1 | G*** | kibuzzard-6A22543C | kibuzzard-6A22543C |
| 1 | G*** | kibuzzard-6A2254F6 | kibuzzard-6A2254F6 |
| 1 | G*** | kibuzzard-6A225388 | kibuzzard-6A225388 |
| 1 | G*** | kibuzzard-6A2263B9 | kibuzzard-6A2263B9 |
| 1 | G*** | kibuzzard-6A226669 | kibuzzard-6A226669 |
| 1 | LED_RED | LED_SMD:LED_0805_2012Metric | D1 |
| 1 | L_Ferrite | Inductor_SMD:L_0805_2012Metric | L1 |
| 1 | MAX-M10S | RF_GPS:ublox_MAX | U1 |
| 1 | PESD0402-140 | Diode_SMD:D_SOD-923 | D2 |
| 1 | QWIIC | project_footprints:CONN_SM04B-SRSS-TB_JST | J6 |
| 1 | power_sw | Button_Switch_SMD:SW_SPDT_PCM12 | SW1 |
Questions
How big is the Pps watch PCB?
It measures 56 × 56 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Pps watch use?
39 parts, built around the 74HC125D, 74AHC1G86SE, MAX-M10S and BU2450SM-JJ-GTR. 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 Pps watch KiCad files?
From the idlehandsdev/pps-watch repository on GitHub, at the commit this page was made from: the board is kicad/pps_watch.kicad_pcb and its schematic kicad/pps_watch.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Pps watch design in my own project?
Its repository publishes it under the AGPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).
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