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

J_D8 Pin_5 - U_LVL 2A
K1 COIL_2 - Q1 C
K1 NC - J_RELAY 3
R_RELAY_B P1 - J_D8 Pin_8
U_LVL 3Y - J_SD D3
R_RELAY_B P2 - Q1 B
K1 NO - J_RELAY 2
K1 COIL_2 - Q1 C
K1 COIL_2 - Q1 C
U_LDO VOUT - C_LDO_OUT P1
J_D8 Pin_4 - J_SD D0
U_LDO VOUT - C_LDO_OUT P1
L_BUCK P2 - C_BUCK_OUT P1
U_LDO VOUT - C_LDO_OUT P1
K1 COM - J_RELAY 1
L_BUCK P2 - C_BUCK_OUT P1
J_D8 Pin_6 - U_LVL 1A
U_LDO EN - K1 COIL_1
U_LDO VOUT - C_LDO_OUT P1
J_D8 Pin_2 - U_LVL 4A
U_LVL 4Y - U_RFID NSS/P50_SCL/HSU_RX
U_BUCK SW - L_BUCK P1
J_D8 Pin_2 - U_LVL 4A
J_D8 Pin_3 - U_LVL 3A
J_D8 Pin_3 - U_LVL 3A
U_BUCK GND - C_BUCK_OUT P2
C_BUCK_IN
Capacitance
10uF
C1
Capacitance
0.1uF
C_LVL
Capacitance
0.1uF
U_BUCK GND - C_BUCK_OUT P2
U_RFID TVSS2 - U_RFID EP
U_RFID TVSS2 - U_RFID EP
U_BUCK GND - C_BUCK_OUT P2
U_LVL *2OE - U_LVL *3OE
GND
U_RFID TVSS2 - U_RFID EP
Q1 E - R_RELAY_PD P2
U_BUCK GND - C_BUCK_OUT P2
U_LVL *2OE - U_LVL *3OE
C_LDO_OUT
Capacitance
1.0uF
C2
Capacitance
0.1uF
GND
C_LDO_IN
Capacitance
1.0uF
C_BUCK_OUT
Capacitance
22uF
U_LVL
Q1
J_RELAY
J_D8
J_PWR
K1
D_FLY
Not Recommended for New Designs
L_BUCK
Inductance
10uH

Arduino RFID SD Relay Shield

Arduino RFID SD Relay Shield thumbnail