2 layers66 × 117 mm
2 layers66 × 117 mm
Input32DC
DavidMFlynn/SerialMRRC1Serial Model Railroad Control
- Size
- 66 × 117 mm
- Copper layers
- 2
- Thickness
- 1.6 mm
- Parts
- 224
- Nets
- 158
- Pads
- 587
- Tracks, vias
- 1,458, 204
- Pours
- 1
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 23 Mar 2025
- Updated
- 2 Oct 2026
Overview
Input32DC is an open-source printed circuit board by DavidMFlynn, from the DavidMFlynn/SerialMRRC repository on GitHub, published under the MIT licence. It is a 2-layer board of 66 × 117 mm with 224 parts on 158 nets, routed with 1,458 tracks and 204 vias.
It is built around the 74HC251D, 74HC138 and 1N4148W. Its parts include 100 resistors, 40 capacitors, 37 diodes, 32 transistors and 6 ICs. It belongs with the interfaces and adapters boards of this library.
Main components
3
74HC251D
SOIC-16-40℃~+125℃ 14ns@6.0V,50pF 160uA 2V~6V 5.2mA 5.2mA 74HC 8/2 Multiplexer Output enable high-impedance、Tri-state output Single Supply SOIC-16 Signal Switches, Multiplexers, Decoders ROHSNexperiaSignal Switches, Multiplexers, Decoders74HC138
SOP-160℃~+70℃ 24ns@5.0V,16pF 2V~6V 3/8 5.2mA 5.2mA 5uA 74HC Decoder Reverse function Single Supply SOP-16 Signal Switches, Multiplexers, Decoders ROHSGRSignal Switches, Multiplexers, Decoders
1N4148W
SOD-123150mA 1A 1V@50mA 1uA@75V 400mW 4ns 75V Independent SOD-123 Switching Diodes ROHSSTMicroelectronicsSwitching Diodes
README
README.mdSerialMRRC
Serial Model Railroad Control
This is a set of PCBs and software to control a model railroad with RS485 data buss.
Stand Alone Boards
Controller Board, PIC15F15345, 1KB Ram, 224B Flash, 8KW Program memory Switch Machine, 1 servo, 1 DPDT relay Switch Machine and Signals, 1 servo, 1 DPDT relay, 5 Signal heads
Daughter Cards
USB Daughter Board Input 32 Daughter Bouad, 32 Pull-to-Ground inputs Output 32 Daughter Board, 32 Open collector Pull-to-Ground outputs Lighting 8x Transistot Outputs, +12v resistor current limited outputs
Anamation Controller, 8 servos Block Detector, detects voltage across diode/resistor Optical Detector, broken beam or reflected beam
USB Operation
When a command packet is received from RX2 (USB): Source=Master, Destination=Me: Parse and Process the command. Send any requested data back to Master on TX2 (USB). Source=Master, Destination<>Me: Retransmit on TX1 (RS485)
When a command packet is received from RX1 (RS485): Source=any, Destination=Me: Parse and Process the command. Send any requested data back to the sender on TX1 (RS485). Source=any, Destination=Master: Retransmit on TX2 (USB) Source=any, Destination= other than Master or Me do nothing.
Node (w/o USB)
When a command packet is received from RX1 (RS485): Source=any, Destination=Me: Parse and Process the command. Send any requested data back to the sender on TX1 (RS485). Source=any, Destination<>Me do nothing.
Parts
224| Qty | Value | Footprint | References |
|---|---|---|---|
| 39 | 0.1uF | Capacitor_SMD:C_0805_2012Metric_Pad1.18x1.45mm_HandSolder | C2, C10, C11, C12, C13, C14, C15, C16, C17, C18, C19, C20, C21, C22, C23, C24 +23 |
| 32 | 10K | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R2, R5, R11, R14, R17, R20, R23, R33, R35, R37, R39, R41, R43, R45, R47, R57 +16 |
| 32 | 1N4148W | Diode_SMD:D_SOD-123 | D2, D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23, D24 +16 |
| 32 | 2K2 | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R1, R6, R12, R15, R18, R21, R24, R34, R36, R38, R40, R42, R44, R46, R48, R58 +16 |
| 32 | 2N3906 | Package_TO_SOT_THT:TO-92_Inline | Q2, Q10, Q11, Q12, Q13, Q14, Q15, Q16, Q17, Q18, Q19, Q20, Q21, Q22, Q23, Q24 +16 |
| 32 | 47K | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R3, R4, R10, R13, R16, R19, R22, R25, R26, R27, R28, R29, R30, R31, R32, R49 +16 |
| 4 | 1206 LED | LED_SMD:LED_1206_3216Metric_Pad1.42x1.75mm_HandSolder | D34, D35, D36, D37 |
| 4 | 1K0 | Resistor_SMD:R_0805_2012Metric_Pad1.20x1.40mm_HandSolder | R97, R98, R99, R100 |
| 4 | 74HC251 | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U2, U3, U4, U5 |
| 2 | Conn_01x16 | TerminalBlock_Phoenix:TerminalBlock_Phoenix_PT-1,5-16-3.5-H_1x16_P3.50mm_Horizontal | J2, J3 |
| 2 | MountingHole | MountingHole:MountingHole_4.3mm_M4 | H5, H6 |
| 2 | MountingHole | MountingHole:MountingHole_3.2mm_M3 | H1, H2 |
| 2 | SolderJumper_3_Bridged12 | Jumper:SolderJumper-3_P1.3mm_Bridged12_RoundedPad1.0x1.5mm | JP1, JP2 |
| 1 | 10uF | Capacitor_THT:CP_Radial_D5.0mm_P2.00mm | C1 |
| 1 | 74HC138 | Package_SO:SOIC-16_3.9x9.9mm_P1.27mm | U1 |
| 1 | Conn_02x06_Odd_Even | Connector_PinHeader_2.54mm:PinHeader_2x06_P2.54mm_Vertical | J1 |
| 1 | L78L05_SOT89 | Package_TO_SOT_SMD:SOT-89-3 | U6 |
| 1 | SMA | Diode_SMD:D_SMA_Handsoldering | D1 |
Questions
How big is the Input32DC PCB?
It measures 66 × 117 mm and has 2 copper layers, 1.6 mm thick.
What parts does the Input32DC use?
224 parts, built around the 74HC251D, 74HC138 and 1N4148W. 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 Input32DC KiCad files?
From the DavidMFlynn/SerialMRRC repository on GitHub, at the commit this page was made from: the board is Input 32 Daughter PCB/Input32DC.kicad_pcb and its schematic Block Relay PCB/BlockRelay.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Input32DC 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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