2 layers87.5 × 72 mm Switchdecoder3, the printed circuit board in 3D

Switchdecoder3

NMRA DCC Compatible Accessory Decoder

Size: 87.5 × 72 mm
Copper layers: 2
Thickness: 0.6 mm
Parts: 1,296
Nets: 32
Pads: 3,906
Tracks, vias: 8,840, 520
Pours: 880
Routed: Yes
KiCad: KiCad 6 (file 20211014)
Created: 6 Nov 2022
Updated: 1 Feb 2026

Overview

Switchdecoder3 is an open-source printed circuit board by ytsurui, from the ytsurui/SwitchDecoder3 repository on GitHub, published under the MIT licence. It is a 2-layer board of 87.5 × 72 mm with 1,296 parts on 32 nets, routed with 8,840 tracks and 520 vias.

It is built around the ATTINY406-MN, SS2040FL and DMG6601LVT, with the 2SC4116 and PMBT3904VS among its other parts. Its parts include 440 resistors, 280 connectors, 200 diodes, 160 capacitors and 160 transistors. It belongs with the AVR (ATmega, ATtiny) boards of this library.

Main components

README

README.md

SwitchDecoder3

PCB Preview

NMRA DCC規格のアクセサリパケットを受信して、直流二線式のポイント線路を動作させることができるアクセサリデコーダです。

本リポジトリには、基板設計データとファームウェア、動作確認用ファームウェアが含まれています。

開発環境

KiCad 6.0.8
Microchip Studio Version 7.0.2542

主要スペック

組み立て後の基板サイズ: 15.5mm x 8.0mm
推奨最大電圧: 16V
出力電流: 最大2A (ピーク3A)
マイコン書き込み端子を用意し、実装後のプログラム書き換えも可能
UPDI 2pin Interface (GND / UPDI)

通常ファームウェア (Firmware)

設定したアクセサリアドレスに応じたDCCパケットを受信すると、ポイント線路を動作させます。

通電開始時にPROG端子に取り付けた配線をどちらかの線路に接触させることで、プログラムモードで起動します。

プログラムモードで起動している間に、同一のアクセサリアドレスに対する操作を連続して3回以上送信することで、設定されているアクセサリアドレスを送信したものに変更することができます。

また、CV値の書き込みにより、通電時間や通電開始までの遅延時間など、細かい動作の調整や、設定のリセットも可能です。

動作確認用ファームウェア (Firm_Test)

アクセサリアドレス「1」固定でDCCパケットを受信して動作できる機能と、PROG端子を線路に接触させると約1秒おきにポイント線路の転換動作を行うようにプログラムを作成してあります。

このファームウェアを書き込むことで、SwitchDecoder3基板のDCC入力、PROG端子、モータードライバ回路のすべてをテストすることができます。

各種ドキュメント

Parts

1,296

Qty	Value	Footprint	References
160	102	footprint:R_1608	R11, R13, R102, R103, R106, R107, R113, R114, R117, R118, R121, R123, R126, R129, R135, R136 +144
160	104	footprint:R_1608	R1, R10, R100, R101, R109, R110, R111, R112, R119, R120, R127, R128, R131, R132, R133, R134 +144
160	PAD	footprint:PAD_2.2x0.8_SMD	P1, P100, P101, P102, P106, P107, P108, P109, P110, P111, P113, P114, P120, P121, P122, P123 +144
160	SS2040FL	footprint:PMDU	D1, D11, D101, D102, D103, D104, D106, D107, D108, D109, D111, D112, D113, D114, D116, D117 +144
80	104	footprint:C_1005	C1, C11, C101, C102, C105, C106, C109, C111, C113, C115, C117, C119, C121, C122, C125, C126 +64
80	331	footprint:R_1608	R14, R15, R104, R105, R115, R116, R124, R125, R137, R138, R148, R149, R159, R160, R170, R171 +64
80	DMG6601LVT	footprint:SOT-23-6	Q1, Q10, Q101, Q102, Q104, Q106, Q109, Q110, Q113, Q114, Q117, Q118, Q121, Q122, Q124, Q126 +64
40	182	footprint:C_1005	C12, C100, C107, C108, C112, C116, C120, C127, C128, C132, C136, C140, C147, C148, C152, C156 +24
40	226	footprint:C_1608	C10, C14, C103, C104, C110, C114, C118, C123, C124, C130, C134, C138, C143, C144, C150, C154 +24
40	2SC4116	footprint:SC-70_v2	Q12, Q100, Q105, Q108, Q112, Q116, Q120, Q125, Q128, Q132, Q136, Q140, Q145, Q148, Q152, Q156 +24
40	472	footprint:R_1608	R12, R20, R108, R122, R130, R141, R152, R163, R177, R185, R196, R207, R218, R232, R240, R251 +24
40	ATtiny406-M	footprint:VQFN-20-1EP_3x3mm_P0.4mm_EP1.7x1.7mm	U2, U10, U11, U12, U13, U14, U15, U16, U17, U18, U19, U20, U21, U22, U23, U24 +24
40	PMBT3904VS	footprint:SOT-666-nomark	Q11, Q15, Q103, Q107, Q111, Q115, Q119, Q123, Q127, Q131, Q135, Q139, Q143, Q147, Q151, Q155 +24
40	PROG	footprint:PAD_PROG_2PIN_HOLE0.7	P12, P19, P103, P112, P117, P124, P131, P138, P147, P152, P159, P166, P173, P182, P187, P194 +24
40	PROG_PAD	footprint:PAD_1.0x1.8_SMD	P11, P14, P105, P116, P119, P126, P133, P140, P151, P154, P161, P168, P175, P186, P189, P196 +24
40	Test	footprint:Test_4pin_2mm	P10, P13, P104, P115, P118, P125, P132, P139, P150, P153, P160, P167, P174, P185, P188, P195 +24
40	UDZV5.1B	footprint:UMD2	D10, D15, D100, D105, D110, D115, D120, D125, D130, D135, D140, D145, D150, D155, D160, D165 +24

The 1,280 most common of 1,296 parts.

Questions

How big is the Switchdecoder3 PCB?

It measures 87.5 × 72 mm and has 2 copper layers, 0.6 mm thick.

What parts does the Switchdecoder3 use?

1,296 parts, built around the ATTINY406-MN, SS2040FL, DMG6601LVT and 2SC4116. 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 Switchdecoder3 KiCad files?

From the ytsurui/SwitchDecoder3 repository on GitHub, at the commit this page was made from: the board is Board/Panelized/switchdecoder3.kicad_pcb and its schematic Board/KiCad/switchdecoder3.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Switchdecoder3 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).

Category and platform

AVR (ATmega, ATtiny)

Project files

Show this board on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/boards/ytsurui-switchdecoder3-switchdecoder3-2" title="Switchdecoder3 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/ytsurui-switchdecoder3-switchdecoder3-2.jpg" alt="Switchdecoder3" width="1200" height="900">

A picture that opens the board, for a README

[![Switchdecoder3](https://pcbkit.io/embed/boards/ytsurui-switchdecoder3-switchdecoder3-2.jpg?size=s)](https://pcbkit.io/boards/ytsurui-switchdecoder3-switchdecoder3-2)

Source

Repository: ytsurui/SwitchDecoder3
Board file: Board/Panelized/switchdecoder3.kicad_pcb
Commit: 8bc3eb4
Licence: MIT

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