Arduino Hat Design Inquiry


I’ll build this as a fully integrated Arduino Uno shield: select ICs/connectors, size the 28 V→5 V power path, wire the schematic per datasheets, then run checks and create the required documentation.
Part selection is underway. I found a PN532 RFID IC and a 5 V relay with verified 120 VAC-capable contacts; the wide-input buck IC search needs a library fallback because the first pass only found module-style entries.
Main ICs are added. I’m now adding the required passives and will wire power, SPI level shifting, microSD, relay driver, and safe relay contact terminals.
I started the fully integrated Arduino Uno shield schematic and renamed the project to Arduino RFID SD Relay Shield.
Completed:
  • Added PN532 RFID IC, microSD socket, relay, relay driver, flyback diode, MP1584 buck, 3.3 V LDO, SPI level shifter, terminal blocks, Arduino header placeholders, and support passives.
  • Wired the initial 28 V input, 5 V rail, 3.3 V rail, SPI level-shift path, relay driver, and relay contacts.
  • Created:
Important: the schematic is not layout-ready yet. Review still reports unresolved floating pins, mainly because the MP1584 buck support network and PN532 crystal/antenna/matching/reset circuitry need to be completed from the datasheets before moving to PCB layout.
Complete missing circuits
Fix ERC warnings
Improve Arduino headers
Add protection features
Prepare for layout

3D view of the PCB of Arduino RFID SD Relay Shield

Arduino RFID SD Relay Shield

Arduino RFID SD Relay Shield thumbnail