2 layers58 × 47 mm Timer Unit, the printed circuit board in 3D

Timer Unit

Code for an i8088-based non-PC compatible breadboard computer

Size: 58 × 47 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 12
Nets: 40
Pads: 106
Tracks, vias: 253, 6
Pours: 1
Routed: Yes
KiCad: KiCad 10.0 (file 20260206)
Created: 25 Apr 2026
Updated: 20 Jul 2026

Overview

Timer Unit is an open-source printed circuit board by oberrow, from the oberrow/i8088-computer repository on GitHub, published under the MIT licence. It is a 2-layer board of 58 × 47 mm with 12 parts on 40 nets, routed with 253 tracks and 6 vias.

It is built around the 74LS540PC, 74LS139PC and NE555P. Its parts include 5 capacitors, 4 ICs, 2 resistors and 1 connector.

Main components

Parts

Qty	Value	Footprint	References
5	C	Capacitor_THT:C_Disc_D5.0mm_W2.5mm_P2.50mm	C1, C2, C3, C4, C5
2	R	Resistor_THT:R_Axial_DIN0207_L6.3mm_D2.5mm_P10.16mm_Horizontal	R1, R2
1	74LS139	Package_DIP:DIP-16_W7.62mm	U3
1	74LS540	Package_DIP:DIP-20_W7.62mm	U4
1	74LV8154	Package_DIP:DIP-20_W7.62mm	U2
1	Conn_01x28	Connector_PinHeader_2.54mm:PinHeader_2x14_P2.54mm_Vertical	J1
1	NE555P	Package_DIP:DIP-8_W7.62mm	U1

Questions

How big is the Timer Unit PCB?

It measures 58 × 47 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Timer Unit use?

12 parts, built around the 74LS540PC, 74LS139PC 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 Timer Unit KiCad files?

From the oberrow/i8088-computer repository on GitHub, at the commit this page was made from: the board is kicad/Timer_Unit/Timer_Unit.kicad_pcb and its schematic kicad/82C55_GPIO_Unit/82C55_GPIO_Unit.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Timer Unit 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).

Project files

Show this board on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/boards/oberrow-i8088-computer-timer-unit" title="Timer Unit in PCBKit" width="100%" height="480" style="border:0;border-radius:12px" allow="fullscreen" loading="lazy"></iframe>

A picture

<img src="https://pcbkit.io/embed/boards/oberrow-i8088-computer-timer-unit.jpg" alt="Timer Unit" width="1200" height="900">

A picture that opens the board, for a README

[![Timer Unit](https://pcbkit.io/embed/boards/oberrow-i8088-computer-timer-unit.jpg?size=s)](https://pcbkit.io/boards/oberrow-i8088-computer-timer-unit)

Source

Repository: oberrow/i8088-computer
Board file: kicad/Timer_Unit/Timer_Unit.kicad_pcb
Commit: c8e67d8
Licence: MIT

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