# Arduino RFID SD Relay Shield ## Description Fully integrated Arduino Uno shield with 13.56 MHz RFID reader, microSD card interface, isolated relay output for a 120 VAC signal circuit, and 28 VDC to 5 V buck power input. ## Project Details - **Owner:** jrmyhrt - **Created:** 6/8/2026 - **Last Updated:** 6/8/2026 - **Visibility:** Public ## Key Components ### D_FLY — [1N4148W](https://www.flux.ai/vasy_skral/1n4148w~vq5.md) - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Clamp relay coil inductive kick when Q1 turns off - Datasheet URL: https://mm.digikey.com/Volume0/opasdata/d220001/medias/docus/7158/5272_1N4148W.pdf - Manufacturer Name: EVVO - Manufacturer Part Number: 1N4148W - Part Type: Diode - Role: Flyback Protection **Pins:** - A [pin 2] - K [pin 1] ### J_D8 — [Pin Header 01x08 2.54mm Horizontal](https://www.flux.ai/adrian95/pin-header-01x08-254mm-horizontal~0e0.md) - Part Type: Connector - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: Uno shield digital header position placeholder - Role: Arduino Header **Pins:** - Pin_1 [pin 1] - Pin_2 [pin 2] - Pin_3 [pin 3] - Pin_4 [pin 4] - Pin_5 [pin 5] - Pin_6 [pin 6] - Pin_7 [pin 7] - Pin_8 [pin 8] ### J_IN — [DB127V-5.08-2P-GN-S](https://www.flux.ai/cherepanyadima/db127v-5p08-2p-gn-s~ic.md) - Datasheet URL: https://www.lcsc.com/datasheet/C3018698.pdf?spm=wm.sxq.inf.ggs&lcsc_vid=ElhbUlFSRlUNBF0CQlQIBQBUFFILBFEAQVVWUgZWE1gxVlNRQVVdVFRSQ1daVDsOAxUeFF5JWBYZEEoBGA4JCwFIFA4DSA%3D%3D - Manufacturer Part Number: DB127V-5.08-2P-GN-S - Part Type: Connector - Role Details: 28 VDC input terminal block for buck regulator - Role: Power Input - Manufacturer Name: DORABO **Pins:** - 1 [pin 1] - 2 [pin 2] ### J_PWR — [Pin Header 01x06 2.54mm PROGRAMMING CONNECTOR](https://www.flux.ai/zalak201285/pin-header-01x06-2p54mm-programming-connector~ji.md) - Role Details: Uno shield header footprint placeholder for power pins - Role: Arduino Header - License: https://creativecommons.org/licenses/by/4.0/ - Part Type: Connector **Pins:** - JTCK [pin 2] - JTDI [pin 1] - JTDO [pin 3] - JTMS [pin 4] - NJTRST [pin 5] - RESET [pin 6] ### J_RELAY — [1729131](https://www.flux.ai/adrian95/1729131~00i.md) - License: https://creativecommons.org/licenses/by/4.0/ - Role: Relay Output Connector - Manufacturer Part Number: 1729131 - Datasheet URL: http://www.phoenixcontact.net/product/1729131 - Role Details: COM/NO/NC terminal for isolated 120 VAC signal circuit - Part Type: Connector - Manufacturer Name: Phoenix Contact - Package or Case Code: 1729131 **Pins:** - 1 [pin 1] - 2 [pin 2] - 3 [pin 3] ### J_SD — [DS1139-06-08SS4BSR](https://www.flux.ai/adrian95/ds1139-06-08ss4bsr~yrz.md) - Part Type: Connector - Role: Memory Card Socket - Datasheet URL: https://www.lcsc.com/datasheet/C86574.pdf - Connector Type: Card Edge Connectors - Role Details: microSD socket wired for SPI mode - Manufacturer Part Number: DS1139-06-08SS4BSR - LCSC Part Number: C86574 - Manufacturer Name: CONNFLY Elec - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - CLK [pin 5] - CMD [pin 3] - D0 [pin 7] - D1 [pin 8] - D2 [pin 1] - D3 [pin 2] - GND [pin 9] - GND [pin 12] - GND [pin 10] - GND [pin 11] - VDD [pin 4] - VSS [pin 6] ### J1 — [Pin Header 01x08 2.54mm Horizontal](https://www.flux.ai/adrian95/pin-header-01x08-254mm-horizontal~0e0.md) - License: https://creativecommons.org/licenses/by/4.0/ - Role: Arduino Header - Role Details: Uno shield digital header position placeholder - Part Type: Connector **Pins:** - Pin_1 [pin 1] - Pin_2 [pin 2] - Pin_3 [pin 3] - Pin_4 [pin 4] - Pin_5 [pin 5] - Pin_6 [pin 6] - Pin_7 [pin 7] - Pin_8 [pin 8] ### K1 — [PR2-5V-450-1C](https://www.flux.ai/adrian95/pr2-5v-450-1c~nlr.md) - Role Details: SPDT 5 V relay; contacts rated up to 250 VAC, use for 120 VAC signal circuit with isolation spacing - Datasheet URL: https://www.cuidevices.com/product/resource/pr2.pdf - Manufacturer Part Number: PR2-5V-450-1C - Manufacturer Name: CUI Devices - Role: Relay - Part Type: Relay - License: https://creativecommons.org/licenses/by/4.0/ **Pins:** - COIL_1 [pin 1] - COIL_2 [pin 2] - COM [pin 3] - NC [pin 5] - NO [pin 4] ### Q1 — [MMBT2222ALT3G](https://www.flux.ai/adrian95/mmbt2222alt3g~vum.md) - Manufacturer Name: onsemi - Manufacturer Part Number: MMBT2222ALT3G - Datasheet URL: https://www.onsemi.com/pdf/datasheet/mmbt2222lt1-d.pdf - License: https://creativecommons.org/licenses/by/4.0/ - Role: Relay Driver - Role Details: NPN low-side driver for 5 V relay coil - Part Type: Transistor **Pins:** - B [pin 1] - C [pin 3] - E [pin 2] ### U_BUCK — [MP1584](https://www.flux.ai/monolithicpower/mp1584~bk.md) - Role: Buck Regulator - Package or Case Code: SOIC8E_MPS - Product Info Url: https://www.monolithicpower.com/en/catalog/product/view/id/109?utm_source=ultralibrarian&utm_medium=component_search&utm_campaign=listing - Datasheet URL: https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP1584EN-LF-Z - Manufacturer Part Number: MP1584 - Role Details: 28 V input to 5 V rail; preliminary load budget about 500 mA peak including Arduino, relay, PN532, and microSD - Manufacturer Name: Monolithic Power Systems - Product Image Url: https://www.monolithicpower.com/pub/media/catalog/product/M/P/MP1584_109_1_3.jpg **Pins:** - BST [pin 8] - COMP [pin 3] - EN [pin 2] - FB [pin 4] - FREQ [pin 6] - GND [pin EPAD] - GND [pin 5] - SW [pin 1] - VIN [pin 7] ### U_LDO — [MIC5504-3.3YM5](https://www.flux.ai/kicad-part-library/mic5504-3p3ym5~ud0.md) - Part Type: Integrated Circuit - Role Details: 3.3 V rail for PN532, microSD, and SPI level shifting - Package or Case Code: SOT-23-5 - Manufacturer Name: Microchip Technology Inc. - Manufacturer Part Number: MIC5504-3.3YM5 - Role: LDO Regulator - Datasheet URL: http://ww1.microchip.com/downloads/en/DeviceDoc/MIC550X.pdf **Pins:** - EN [pin 3] - GND [pin 2] - NC [pin 4] - VIN [pin 1] - VOUT [pin 5] ### U_LVL — [SN74LVC125AQDRQ1](https://www.flux.ai/adrian95/sn74lvc125aqdrq1~e55.md) - License: https://creativecommons.org/licenses/by/4.0/ - Manufacturer Part Number: SN74LVC125AQDRQ1 - Role: Level Shifter - Role Details: 3.3 V powered LVC buffer for Arduino 5 V SPI outputs into PN532 and microSD - Part Type: Integrated Circuit - Manufacturer Name: Texas Instruments - Datasheet URL: https://www.ti.com/lit/ds/symlink/sn74lvc125a-q1.pdf **Pins:** - *1OE [pin 1] - *2OE [pin 4] - *3OE [pin 10] - *4OE [pin 13] - 1A [pin 2] - 1Y [pin 3] - 2A [pin 5] - 2Y [pin 6] - 3A [pin 9] - 3Y [pin 8] - 4A [pin 12] - 4Y [pin 11] - GND [pin 7] - VCC [pin 14] ### U_RFID — [PN5321A3HN/C106;55](https://www.flux.ai/adrian95/pn5321a3hnc10655~jbv.md) - Package or Case Code: QFN50P600X600X100-41N-D - Manufacturer Name: NXP - Datasheet URL: http://www.nxp.com/docs/en/nxp/data-sheets/PN532_C1.pdf - Manufacturer Part Number: PN5321A3HN/C106;55 - Integrated Circuit Type: RF Device - License: https://creativecommons.org/licenses/by/4.0/ - Role Details: 13.56 MHz PN532 RFID/NFC reader, SPI-connected to Arduino Uno header - Role: RFID Reader - Part Type: Integrated Circuit **Pins:** - AUX1 [pin 12] - AUX2 [pin 13] - AVDD [pin 8] - AVSS [pin 11] - DVDD [pin 39] - DVSS [pin 1] - EP [pin 41] - I0 [pin 16] - I1 [pin 17] - LOADMOD [pin 2] - MISO/P71 [pin 29] - MOSI/SDA/HSU_TX [pin 28] - N.C._1 [pin 20] - N.C._2 [pin 21] - N.C._3 [pin 22] - NSS/P50_SCL/HSU_RX [pin 27] - OSCIN [pin 14] - OSCOUT [pin 15] - P30/UART_RX [pin 24] - P31/UART_TX [pin 31] - P32_INT0 [pin 32] - P33_INT1 [pin 33] - P34/SIC_CLK [pin 34] - P35 [pin 19] - P70__IRQ [pin 25] - PVDD [pin 23] - RSTOUT_N [pin 26] - RSTPD_N [pin 38] - RX [pin 10] - SCK/P72 [pin 30] - SIGIN [pin 36] - SIGOUT [pin 35] - SVDD [pin 37] - TESTEN [pin 18] - TVDD [pin 5] - TVSS1 [pin 3] - TVSS2 [pin 7] - TX1 [pin 4] - TX2 [pin 6] - VBAT [pin 40] - VMID [pin 9] *The full schematic, PCB layout, bill of materials, and interactive design are available at [https://www.flux.ai/jrmyhrt/arduino-rfid-sd-relay-shield~05](https://www.flux.ai/jrmyhrt/arduino-rfid-sd-relay-shield~05).* --- *Generated from [https://www.flux.ai/jrmyhrt/arduino-rfid-sd-relay-shield~05](https://www.flux.ai/jrmyhrt/arduino-rfid-sd-relay-shield~05)*