2 layers159.5 × 30 mm
Type f
google/mozc-devices
Circuit diagrams and firmware source code for Gboard DIY keyboards
25 parts3kApache-2.0
2 layers45.1 × 48.5 mm
TTL SIREN
Gabouin/TTL-SIREN2TTL Based Police Siren A TTL logic circuit designed to mimic a police siren using an astable multivibrator. Blue and red LEDs alternate in a blinking pattern, with a custom PCB shaped like a siren light.
- Size
- 45.1 × 48.5 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 25
- Nets
- 8
- Pads
- 40
- Tracks, vias
- 44, 0
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 7 Apr 2026
- Updated
- 30 Apr 2026
Overview
TTL SIREN is an open-source printed circuit board by Gabouin, from the Gabouin/TTL-SIREN repository on GitHub, published under the MIT licence. It is a 2-layer board of 45.1 × 48.5 mm with 25 parts on 8 nets, routed with 44 tracks and 0 vias.
Its parts include 10 diodes, 4 resistors, 2 capacitors, 2 transistors and 1 connector.
README
README.md
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TTL Based Police SirenA TTL logic circuit designed to mimic a police siren using an astable multivibrator. Blue and red LEDs alternate in a blinking pattern, with a custom PCB shaped like a siren light. Designed to fit inside a 3D-printed translucent enclosure for a realistic cosplay prop. |
Table of Contents
- About the Project
- Circuit Simulation
- Schematic Design
- PCB Design
- Bill of Materials
- Production Files
- License
- Contributing
About the Project
The core of this project is an astable multivibrator built from two NPN transistors. The transistors alternately switch on and off: when one turns on, it pulls the other's base voltage low, preventing it from conducting. The capacitors charge and discharge through the resistors, creating a timing delay that causes the transistors to switch states repeatedly — making the LEDs blink back and forth like a siren.
The PCB outline is shaped like a police siren light, with blue LEDs on one side and red LEDs on the other, and components grouped in the centre. The design is intended to fit inside a 3D-printed translucent enclosure for use as a cosplay prop.
This project was made for the 2nd week of RESOLUTION — Hack Club.
Circuit Simulation
An interactive simulation of the circuit is available on Falstad Circuit Simulator:
▶️ Open the Falstad simulation
Schematic Design
The schematic was designed in KiCad. Source files are available in the Sources/KiCad folder.
PCB Design
Component Placement
The PCB edge cut is shaped like a police siren. Blue LEDs are placed on one side and red LEDs on the other, with passive components grouped in the centre.
Silkscreen
Bill of Materials
| Designator | Value | Footprint | Quantity |
|---|---|---|---|
| C1, C2 | 12 µF | C_Disc_D5.0mm_W2.5mm_P5.00mm | 2 |
| D1–D10 | LED | LED_D5.0mm | 10 |
| J1 | Conn_01x02 | PinHeader_1x02_P2.54mm_Vertical | 1 |
| Q1, Q2 | NPN | TO-92L_Inline_Wide | 2 |
| R1, R4 | 330 Ω | R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal | 2 |
| R2, R3 | 1 kΩ | R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal | 2 |
The full BOM is also available as a CSV file in the
productionfolder.
Production Files
Gerber files, drill files, BOM, component positions, and netlist are available in the production folder, ready for PCB fabrication.
License
This project is licensed under the MIT License — see the LICENSE file for details.
Contributing
Contributions, improvements, and remixes are welcome! Please read the CONTRIBUTING.md guide to get started.
Parts
25| Qty | Value | Footprint | References |
|---|---|---|---|
| 10 | LED | LED_THT:LED_D5.0mm | D1, D2, D3, D4, D5, D6, D7, D8, D9, D10 |
| 6 | LOGO | LOGO | G***, G***, G***, G***, G***, G*** |
| 2 | 12u | Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P5.00mm | C1, C2 |
| 2 | 1k | Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal | R2, R3 |
| 2 | 330 | Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal | R1, R4 |
| 2 | NPN | Package_TO_SOT_THT:TO-92L_Inline_Wide | Q1, Q2 |
| 1 | Conn_01x02 | Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical | J1 |
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Questions
How big is the TTL SIREN PCB?
It measures 45.1 × 48.5 mm and has 2 copper layers, 1.6 mm thick.
What parts does the TTL SIREN use?
25 parts. 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 TTL SIREN KiCad files?
From the Gabouin/TTL-SIREN repository on GitHub, at the commit this page was made from: the board is Sources/KiCad/TTL SIREN.kicad_pcb and its schematic Sources/KiCad/TTL SIREN.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the TTL SIREN design in my own project?
Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).