PCB Assembly Challenges
Worked for 1 min 30 sec
Completed the full no-consign JLCPCB audit. Every BOM component now has an LCSC part number, and unavailable/uncertain passive parts were changed to stocked, same-package, equal-or-better electrical alternatives; no footprint or routing changes were required.
Key confirmed stock included:
- ESP32 module
C701346: ~2,358 - DRV8873-Q1
C2150479: ~2,381 - LM5146-Q1
C1850329: ~2,300 - L2
C2047831: ~446 - Q1/Q2
C396083: ~1,990 - F1
C135417: ~825
Checks show no current sourcing/manufacturing or DRC errors. Stock can change before checkout, so JLCPCB’s live BOM matching page remains the final authority.
Updated files:
- Gerbers ZIP
JLCPCB BOM
Comment Designator Footprint JLCPCB Part # LCSC Part # 35YXF2200MFFC16X31.5 C1 C88844 C3225X7R1H106KT000E C2 C432929 CC0603KRX7R7BB224 C3 C106249 CL21A226MPQNNNE C10, C6, C7, C8, C9 C29277 TCC0603X5R105M500CT C11, C13, C15, C5 C20539427 CL10B104KB8NNNC C12, C16, C28, C4 C1591 CL10B473KO8NNNC C14, C29 C2762284 GRM31CR72A225KA73L C17, C18, C19, C20, C21 C913599 CC1210MKX7R9BB226 C22, C23, C24, C25, C26 C914881 CL10A225KL8NNNC C27 C307463 CL10B472JB8NNNC C30 C159797 TCC0603COG101J500CT C31 C344186 SS510 D1, D2, D3, D4 SMC_L6.9-W5.9-LS7.9-R-RD C717458 SMBJ26A-TR D5 SMB_L4.6-W3.6-LS5.3-RD C133666 A30-600 F1 FUSE-TH_L19.1-W3.0-P10.20-D1.2-S2.0 C135417 B2P-VH(LF)(SN) J1, J2 CONN-TH_B2P-VH-LF-SN C160315 VLS6045EX-6R8M L1 C415364 SPM10065VT-6R8M-D L2 IND-SMD_L10.5-W10.0 C2047831 P0603P1N46G12 LED1 C5123548 KT-0603R LED2 C2286 SED10070GG Q1, Q2 DFN-8_L5.1-W5.7-P1.27-LS6.1-BL C396083 RC0603FR-07100KL R1, R8 C14675 AC0603FR-0743K2L R2 C227902 RC0603FR-07820RL R5 C114638 SCR0603F68K R7 C3016380 RC0603FR-07215KL R9 C22954 RC0603FR-0710KL R10, R13, R3, R4, R6 C98220 RC0603FR-0724K9L R11 C137761 CRCW0603174KFKEA R12 C2076698 CR0603FA6190G R14 C101134 RC0603FR-078K06L R15 C131052 RC0603FR-071KL R16, R17 C21190 DRV8873HPWPRQ1 U1 HTSSOP-24_L7.8-W4.4-P0.65-LS6.4-BL-EP5.2 C2150479 74LVC1G04SE-7 U2 SOT-353_L2.2-W1.4-P0.65-LS2.4-BR C264081 LMR33630BDDAR U3 SOIC-8_L4.9-W3.9-P1.27-LS6.0-BL-EP2.8-1 C544370 ESP32-WROOM-32UE-N16 U4 C701346 LM5146QRGYRQ1 U5 VQFN-20_L4.5-W3.5-P0.50-BL-EP-1 C1850329 JLCPCB Pick-and-place
Designator Layer Rotation Mid X Mid Y C1 Top 90 -5mm -27.25mm C2 Bottom 0 -4mm 34mm C3 Bottom 0 -12.5mm 8mm C4 Bottom 90 3.5mm 34mm C5 Bottom 270 0mm 34mm C6 Bottom 180 -12mm 25mm C7 Bottom 180 -8mm 25mm C8 Bottom 180 -4mm 25mm C9 Bottom 180 0mm 25mm C10 Bottom 180 -12mm 30mm C11 Bottom 270 -8mm 30mm C12 Bottom 0 -4mm 30mm C13 Bottom 270 5mm 8mm C14 Bottom 0 8mm 8mm C15 Bottom 180 10.8mm 8mm C16 Bottom 90 12mm 5.5mm C17 Bottom 0 -11.4mm -9mm C18 Bottom 0 -6.8mm -9mm C19 Bottom 0 -2.2mm -9mm C20 Bottom 0 2.4mm -9mm C21 Bottom 0 7mm -9mm C22 Bottom 0 11.2mm -9mm C23 Bottom 0 -10.8mm -13mm C24 Bottom 270 -7mm -13mm C25 Bottom 90 -2mm -13mm C26 Bottom 0 3mm -13mm C27 Bottom 180 -12mm 1mm C28 Bottom 0 -9mm 1mm C29 Bottom 270 -5.5mm 1mm C30 Bottom 90 -2mm 1mm C31 Bottom 0 1.5mm 1mm D1 Top 180 -9.2mm -14mm D2 Top 180 -9.2mm -7mm D3 Top 180 2mm -14mm D4 Top 180 2mm -7mm D5 Top 90 9.5mm -26mm F1 Top 180 0mm -20mm J1 Top 180 9mm -37mm J2 Top 0 10.07mm 36mm L1 Bottom 0 -2.2mm 15mm L2 Top 0 -7mm 4mm LED1 Top 0 -12.2mm 32.2mm LED2 Top 0 -5mm 32.2mm Q1 Top 0 9.63mm -0.8mm Q2 Top 0 10.83mm -8.6mm R1 Bottom 180 -11mm 6mm R2 Bottom 90 -8mm 6mm R3 Bottom 90 0mm 30mm R4 Bottom 0 4mm 30mm R5 Bottom 0 5mm 12mm R6 Bottom 180 8mm 12mm R7 Bottom 0 11mm 12mm R8 Bottom 0 12mm 14mm R9 Bottom 0 5mm -1mm R10 Bottom 270 8mm -1mm R11 Bottom 270 11mm -1mm R12 Bottom 0 -12.5mm -5mm R13 Bottom 180 -9mm -5mm R14 Bottom 0 -5.5mm -5mm R15 Bottom 0 -2mm -5mm R16 Top 0 -8.8mm 32.2mm R17 Top 0 -1.6mm 32.2mm U1 Top 180 9.5mm 7.5mm U2 Bottom 270 11.5mm 18mm U3 Bottom 270 -10.3mm 14.995mm U4 Top 0 -3.4mm 21.03mm U5 Top 180 3mm 1.5mm
Validate and prepare order
Run final DRC
Review 5 A copper
Verify JLCPCB files
Explain BOM matching
Refine this doc
Ask about this doc
Project Specification — TMCC WiFi DCC 5A Module
Project Overview
Draft design for a compact per-locomotive module that accepts 18 VAC from track pickups, rectifies it to a ~24 V DC bus, and regenerates a 5 A bipolar DCC waveform for a stock DCC/MTH decoder. The design uses an assembler-friendly ESP32-WROOM-32UE module instead of a bare Espressif chip.
Intended Use
Installed inside an O-scale locomotive/tender. Prototype-to-small-build design intended for standard PCB fabrication and assembly.
What the Device Should Do
- Take 18 VAC from locomotive track pickups.
- Generate a bipolar DCC output to a decoder at up to 5 A.
- Connect over WiFi to JMRI/WiThrottle and synthesize DCC timing in firmware.
- Monitor H-bridge fault and current-sense signals for overload shutdown.
- Provide an external USB-UART programming/debug header.
Main Features
- 18 VAC input through inline 6 A PTC protection.
- Discrete SS510 Schottky bridge rectifier.
- VBUS transient protection with SMBJ26A TVS.
- DRV8873 H-bridge output stage.
- ESP32-WROOM-32UE WiFi/Bluetooth module with u.FL antenna connection.
- 3.3 V buck regulator from VBUS.
- JST-VH high-current input/output connectors.
System Architecture
Diagram
Power Tree and Power Budget
- 18 VAC input, nominal rectified peak about 25 V.
- DCC output design target: 5 A intermittent/decoder load.
- 3.3 V rail loads: ESP32 WiFi module, 74LVC1G04, DRV8873 logic. Provisional regulator target: >=600 mA peak.
- Open thermal item: DRV8873 continuous 5 A copper/thermal validation.
Manufacturing and Assembly Expectations
- Use real library parts with standard assembler-compatible footprints.
- Avoid bare Espressif chip/RF design; use ESP32-WROOM-32UE certified module with onboard u.FL.
- Prefer SMD passives/power semiconductors except JST-VH and programming header.
- Target board size from source spec: about 30 mm x 24 mm, subject to thermal copper area.
Firmware-Relevant Hardware Requirements
- ESP32 GPIO25 outputs DCC signal via RMT.
- Complementary signal generated through 74LVC1G04 inverter.
- ESP32 controls DRV8873 enable/sleep, reads nFAULT, and samples IPROPI current sense by ADC.
- Programming header exposes 3V3, GND, TX, RX, EN, and IO0.
Physical Design Expectations
- Compact two-layer PCB unless thermal/EMI review requires more copper or layers.
- ESP32-WROOM-32UE u.FL antenna must route to an external antenna suitable for metal locomotive shells.
- DRV8873 PowerPAD requires large copper pour and thermal vias if available.
Important Design Decisions
- Use ESP32-WROOM-32UE module rather than a bare Espressif chip because PCBWay rejected bare Espressif assembly and module RF assembly/certification is safer.
- Use DRV8873 single H-bridge instead of discrete FET gate-driver bridge for compactness and protection.
- Use a high-voltage buck regulator for 3.3 V instead of an LDO due to VBUS near 24 V.
Assumptions
- Transformer nominal is 18 VAC and decoder tolerates DCC amplitude in the expected VBUS range.
- 5 A is intermittent/peak; continuous thermal performance must be bench-verified.
- External USB-UART adapter provides 3.3 V logic only, not 5 V UART.
Change Notes
- Initial project file created from attached DCC-module-design.md.
Project Overview
Intended Use
What the Device Should Do
Main Features
System Architecture
Power Tree and Power Budget
Manufacturing and Assembly Expectations
Firmware-Relevant Hardware Requirements
Physical Design Expectations
Important Design Decisions
Assumptions
Change Notes
