2 layers265.5 × 132.3 mm
Dashdash
Churrosoft/Dashdash
tablero de instrumentos por can para integrar con OpenEFI, cuando se nos ocurra algo mas original cambiamos el nombre
272 parts1MIT
2 layers73 × 77.5 mm
STOPWATCH CIRCUIT
EmilPtr/STOPWATCHA simple stopwatch PCB
- Size
- 73 × 77.5 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 31
- Nets
- 69
- Pads
- 158
- Tracks, vias
- 318, 42
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 9 Mar 2026
- Updated
- 16 Apr 2026
Overview
STOPWATCH CIRCUIT is an open-source printed circuit board by EmilPtr, from the EmilPtr/STOPWATCH repository on GitHub. It is a 2-layer board of 73 × 77.5 mm with 31 parts on 69 nets, routed with 318 tracks and 42 vias.
It is built around the 74AHC595D, HDSP-7801 and LTC-4627JD. Its parts include 17 resistors, 6 ICs, 4 switches and 2 capacitors. It belongs with the AVR (ATmega, ATtiny) boards of this library.
Main components
3
74AHC595D
SOIC-16-40℃~+125℃ 1 170MHz 2V~5.5V 74AHC 8 8mA Serial-to-Serial or Parallel Tri-State SOIC-16 Shift Registers ROHSNexperiaShift Registers
HDSP-7801
插件0.3 1 105mW 12.7mmx7.62mmx6.09mm 7 Segment Common Anode Green 插件 LED Segment Displays ROHSBroadcom LimitedLED Segment Displays
LTC-4627JD
DIP-14DIP-14 LED Segment Displays ROHSLite-OnLED Segment Displays
README
README.mdStopwatch
This is a simple stopwatch PCB that was intended for me to get into the complex world of PCB design and microcontrollers on PCBs. It functions like a regular stopwatch, you cna start the timer, stop it, and reset it, and it has an accuracy to tens of miliseconds.
Schematic
the schematic looks like this, it consists of several HC595 8-bit shift registers to multiplex the MCU's pins for minimal pin usage on displays, some buttons for control, and a 3.3V regulator to regulate a 3xAA battery's voltage to power the MCU in a stable fashion.
PCB
The PCB uses only 2 layers to be as cost effective as possible and stays within 100mm x 100mm to capitalize on JLCPCB's lowest cost threshold. It was designed in a way where traces of similar functionality are grouped together, but not close enough to be affected by other traces by Faraday's Law.
Physical Build
YAYYY ITS DONE!!! :D https://github.com/user-attachments/assets/ebe392f2-ca30-4a46-b4f1-2a95856c1f90
Parts
31| Qty | Value | Footprint | References |
|---|---|---|---|
| 14 | 470R | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R1, R2, R3, R4, R5, R6, R7, R11, R12, R13, R14, R15, R16, R17 |
| 3 | 10k | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R8, R9, R10 |
| 2 | 1u | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C1, C2 |
| 2 | 74AHC595 | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U1, U6 |
| 2 | HDSP-7801 | Display_7Segment:HDSP-7801 | U4, U5 |
| 1 | Arduino_Nano_v2.x | Module:Arduino_Nano | A1 |
| 1 | Battery | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical | BT1 |
| 1 | LTC-4627JD | Display_7Segment:LTC-4627Jx | U2 |
| 1 | SW_RESET | Button_Switch_SMD:SW_Push_1P1T_NO_CK_KSC9xxG | SW3 |
| 1 | SW_SPDT | Button_Switch_THT:SW_Slide_SPDT_Angled_CK_OS102011MA1Q | SW4 |
| 1 | SW_START | Button_Switch_SMD:SW_Push_1P1T_NO_CK_KSC9xxG | SW1 |
| 1 | SW_STOP | Button_Switch_SMD:SW_Push_1P1T_NO_CK_KSC9xxG | SW2 |
| 1 | TC1017-xCT | Package_TO_SOT_SMD:SOT-23-5 | U3 |
Questions
How big is the STOPWATCH CIRCUIT PCB?
It measures 73 × 77.5 mm and has 2 copper layers, 1.6 mm thick.
What parts does the STOPWATCH CIRCUIT use?
31 parts, built around the 74AHC595D, HDSP-7801 and LTC-4627JD. 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 STOPWATCH CIRCUIT KiCad files?
From the EmilPtr/STOPWATCH repository on GitHub, at the commit this page was made from: the board is STOPWATCH_CIRCUIT/STOPWATCH_CIRCUIT.kicad_pcb and its schematic STOPWATCH_CIRCUIT/STOPWATCH_CIRCUIT.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the STOPWATCH CIRCUIT design in my own project?
Its repository states no licence, so its author keeps all rights: ask EmilPtr before reusing the design.
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