2 layers327.9 × 139 mm
Coco2
baldengineer/bit-preserve
Project for capturing vintage, classic, aka old computer schematics in KiCad.
147 parts446
2 layers40 × 70 mm
Lm3914
Rohan317685/RailflashThis is a railroad flasher PCB that uses Astable mode and RC timing to flicker just like a railroad flasher!
- Size
- 40 × 70 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 8
- Nets
- 10
- Pads
- 26
- Tracks, vias
- 25, 0
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 9.0 (file 20241229)
- Created
- 12 Apr 2026
- Updated
- 12 Apr 2026
Overview
Lm3914 is an open-source printed circuit board by Rohan317685, from the Rohan317685/Railflash repository on GitHub, published under the MIT licence. It is a 2-layer board of 40 × 70 mm with 8 parts on 10 nets, routed with 25 tracks and 0 vias.
It is built around the NE555P. Its parts include 3 resistors, 2 diodes, 1 capacitor, 1 IC and 1 connector.
Main components
1README
README.mdRailflash
This is a railroad flasher PCB that uses Astable mode and RC timing to flicker just like a railroad flasher!
Schematic
PCB
BOM
| Reference | Qty | Value | Footprint |
|---|---|---|---|
| C1 | 1 | 10µF | CP_Radial_D5.0mm_P2.50mm |
| D1, D2 | 2 | Red LED | LED_D5.0mm |
| J1 | 1 | USB_A | USB_A_Molex_67643_Horizontal |
| R1, R2 | 2 | 220Ω | R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal |
| R3 | 1 | 47kΩ | R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal |
| U2 | 1 | NE555P | DIP-8_W7.62mm |
Assembly / Usage
R1, R2, R3 (resistors)
U2 (NE555P): insert with notch facing the marked end on silkscreen
C1 (10µF cap): stripe on cap = negative, match to silkscreen
D1, D2 (LEDs): short leg = negative, match to flat side of LED symbol
J1 (USB connector)
Plug into any 5V USB-A source: phone charger, power bank, etc.
LEDs will begin alternating immediately on power up.
To adjust flash speed, change R3 (47kΩ) or C1 (10µF):
- Larger values = slower flash
- Smaller values = faster flash
Parts
8| Qty | Value | Footprint | References |
|---|---|---|---|
| 2 | 220 | Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal | R1, R2 |
| 2 | Red LED | LED_THT:LED_D5.0mm | D1, D2 |
| 1 | 10uf | Capacitor_THT:CP_Radial_D5.0mm_P2.50mm | C1 |
| 1 | 47k | Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P7.62mm_Horizontal | R3 |
| 1 | NE555P | Package_DIP:DIP-8_W7.62mm | U2 |
| 1 | USB_A | Connector_USB:USB_A_Molex_67643_Horizontal | J1 |
Questions
How big is the Lm3914 PCB?
It measures 40 × 70 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Lm3914 use?
8 parts, built around the NE555P. 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 Lm3914 KiCad files?
From the Rohan317685/Railflash repository on GitHub, at the commit this page was made from: the board is src/lm3914.kicad_pcb and its schematic src/lm3914.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Lm3914 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).
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