4 layers71.1 × 99.1 mm
2 layers129.5 × 33 mm
BCD Decade Counter
adhyayan15/BCD_Decade_CounterDesigned a custom KiCad PCB for a BCD decade counter, transitioning a verified breadboard prototype into a manufacturable circuit.
- Size
- 129.5 × 33 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 15
- Nets
- 24
- Pads
- 70
- Tracks, vias
- 122, 1
- Pours
- 2
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 1 Aug 2026
- Updated
- 4 Nov 2026
Overview
BCD Decade Counter is an open-source printed circuit board by adhyayan15, from the adhyayan15/BCD_Decade_Counter repository on GitHub, published under the MIT licence. It is a 2-layer board of 129.5 × 33 mm with 15 parts on 24 nets, routed with 122 tracks and 1 via.
It is built around the HDSP-7503 and NE555P. Its parts include 9 resistors, 4 ICs, 1 capacitor and 1 connector.
Main components
2README
README.mdBCD Decade Counter PCB
A breadboard circuit I turned into a PCB to get more comfortable with digital electronics and KiCad.
This started with a pretty simple goal: make a 7-segment display count from 0 to 9 without using a microcontroller. I first wired the circuit on a breadboard, checked that the counter worked, and then tried to fit the same idea onto a board I could design myself.
The interesting part wasn't the counting. It was figuring out how the clock, counter, decoder, resistors, and display all needed to connect, then translating that into an actual PCB layout.
How it works
NE555 timer (clock)
|
v
74LS90 decade counter (0–9)
|
v
4511 BCD-to-7-segment decoder
|
v
7-segment display (HDSP-7503)The NE555 provides the pulses. The 74LS90 counts them through the ten decimal states. The 4511 translates the BCD output into signals for the display. Seven 220 Ω resistors limit current through the display segments.
The KiCad schematic also includes a 1 kΩ resistor, a 10 kΩ resistor, a polarized capacitor, and a two-pin power connection. I used an external 5 V breadboard power module during prototyping rather than designing a regulator onto this board.
From breadboard to PCB
| PCB layout | Schematic |
|---|---|
 |  |
After getting the breadboard circuit running, I redrew it in KiCad, assigned the through-hole footprints, and routed the board. This was a useful introduction to how much more deliberate you have to be once your wires become copper traces.
Open the editable design
The schematic records KiCad 10.0 as its generating version. Use KiCad 10.0 to review the files in their original tool version.
- Clone or download the whole repository so the project, schematic, and PCB files stay together.
- In KiCad, open KiCad/BCD Decade Counter.kicad_pro.
- Open the schematic to inspect connections, or the PCB to inspect footprints and routing.
The PNGs in Images/ are previews; edit the KiCad source files to change the design. The repository contains no exported Gerber or NC drill files. If preparing a board order, rerun ERC/DRC and generate fabrication outputs from the reviewed PCB first.
Where it stands
- Breadboard: built and tested.
- Schematic and PCB layout: completed.
- ERC/DRC: passed during my design work.
I'm leaving the project as it is for now. It was a small circuit, but it was an important step in going from connecting components to designing the board those components sit on.
Built by Adhyayan Tiwari · MIT License
Parts
15| Qty | Value | Footprint | References |
|---|---|---|---|
| 7 | 220 | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R5, R6, R7, R8, R9, R10, R11 |
| 1 | 10k | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R2 |
| 1 | 1k | Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P7.62mm_Horizontal | R1 |
| 1 | 4511 | Package_DIP:DIP-16_W7.62mm | U3 |
| 1 | 74LS90 | Package_DIP:DIP-14_W7.62mm | U2 |
| 1 | C_Polarized | Capacitor_THT:CP_Radial_D5.0mm_P2.00mm | C1 |
| 1 | Conn_01x02_Pin | TerminalBlock:TerminalBlock_MaiXu_MX126-5.0-02P_1x02_P5.00mm | J1 |
| 1 | HDSP-7503 | Display_7Segment:HDSP-7507 | U4 |
| 1 | NE555P | Package_DIP:DIP-8_W7.62mm | U1 |
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Questions
How big is the BCD Decade Counter PCB?
It measures 129.5 × 33 mm and has 2 copper layers, 1.6 mm thick.
What parts does the BCD Decade Counter use?
15 parts, built around the HDSP-7503 and 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 BCD Decade Counter KiCad files?
From the adhyayan15/BCD_Decade_Counter repository on GitHub, at the commit this page was made from: the board is KiCad/BCD Decade Counter.kicad_pcb and its schematic KiCad/BCD Decade Counter.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the BCD Decade Counter 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).