LoRa PLC Receiver PCB

Thought for 19 sec

Existing project files were recovered, so I’m consolidating and upgrading them rather than creating duplicate specifications.

Worked for 2 mins 50 sec

Created a project doc

Preliminary BOM

View Document

Preliminary BOM Status and Use

Preliminary architecture BOM for schematic capture and sourcing review. Quantities are per receiver. MPNs must be rechecked against current datasheets, distributor stock, lifecycle, module certification, and Flux footprint quality before purchase or PCB release.

Recommended Core Components Power Input and Protection Buck Regulator Support Components Logic, Reset and Decoupling Relay Drivers and Indicators Field and RF Connectors Timing Components for External Watchdog Mechanical and Assembly Items Preliminary Cost and Sourcing Notes

Relays, pluggable terminals, radio module, enclosure, and assembly labor are expected to dominate unit cost.

flux

The detailed specification and BOM are now drafted. I found and corrected a critical inconsistency in the earlier notes: communications relays must be energized when healthy and use COM–NC so loss of receiver power produces an alarm.

Thought for 7 sec

flux

Created the detailed Project Specification and Preliminary BOM, including architecture, fail-safe COM–NC communications alarms, power budget, interfaces, PCB/enclosure requirements, verification criteria, recommended MPNs, and alternatives. Remaining work is final datasheet/availability verification for the radio SKU, relays, power supply, antenna certification conditions, Siemens input module, and enclosure; further execution is paused because no ACUs are currently available.

Check BOM availability

Verify critical datasheets

Create receiver schematic

Document open items

No schematic yet

Talk to Flux to get started.

Preliminary BOM

Status and Use

Recommended Core Components

Table

Ref. group	Qty	Function	Preferred part / MPN	Key requirement and rationale	Alternatives / notes
U1	1	Host MCU	STM32G030C8T6	3.3 V Cortex-M0+, LQFP-48, UART, I2C/SPI, timers, SWD, independent watchdog, sufficient GPIO	STM32G071CBT6 for more memory/peripherals
U2	1	EU868 LoRa module	RAK3172, EU868 SKU	Pre-certified STM32WLE5-based module, EU868 support, external 50-ohm RF connection	Seeed LoRa-E5; Ezurio 453-00139R after certification/interface review
U3	1	24 V to 5 V buck	TI LM5013DDAR	6–100 V input gives strong industrial transient margin; output configured to 5 V; ample current	TI LMR36510/LMR38010 family if a 60–65 V part with simpler implementation is preferred; LMR50410 only if 36 V limit is acceptable after transient analysis
U4	1	5 V to 3.3 V LDO	AP7361C-33E-13 or equivalent 1 A thermally capable LDO	At least 300 mA rating with package/copper capable of about 0.32 W worst-case preliminary dissipation	TLV75533PDBVR may be used only after thermal verification; buck-to-3.3 V is an option if measured radio load is high
U5	1	GPIO expander	MCP23017T-E/SO	16 I/O over I2C for reel relays and indicators	Omit if MCU GPIO allocation allows direct drive
U6	1	Reel relay driver	ULN2803ADWR	Eight low-side channels with integrated clamp diodes	Eight individual 2N7002-class MOSFETs plus flyback diodes
U7	1	Dual missing-pulse watchdog	CD74HC4538PWR	Dual retriggerable monostable; firmware services each channel only while corresponding radio link is healthy	Two dedicated TPS3431-class watchdogs; timing network and startup behavior must be verified
U8	1	Communications relay driver/buffer	74HC14 or dual transistor/MOSFET stage	Conditions watchdog outputs and ensures relay energizes only on valid recurring service pulses	Two discrete 2N7002 MOSFET stages with defined pull-downs
K1–K10	10	Form-C dry-contact relay	Omron G5V-1-DC5	5 V coil, low approximately 150 mW coil power, SPDT/Form-C, compact THT signal relay	Omron G6S-2-DC5 DPDT using one pole; confirm exact suffix, footprint, contact rating, and stock

Power Input and Protection

Table

Ref. group	Qty	Function	Preferred part / class	Preliminary rating	Notes
J1	1	24 V input connector	Phoenix Contact MSTB 2,5/2-ST-5,08 compatible pair	At least 5 A, 30 VDC+	Select exact horizontal/vertical header and mating plug
F1	1	Input fuse	0.5 A time-delay replaceable fuse or coordinated PTC	Voltage rating at least 32 VDC, preferably 60 VDC	Final rating from inrush, wiring and TVS fault study
Q1	1	Reverse-polarity MOSFET	60 V P-channel MOSFET, low RDS(on)	At least 1 A and suitable SOA	Example family: DMP-series 60 V P-MOSFET; exact MPN after topology calculation
D1	1	Input TVS	SMBJ33CA-class bidirectional TVS	Standoff compatible with 30 V max input	Verify clamp against buck absolute maximum and panel transient standard
FB1/L1	1	Input EMI element	Ferrite bead or small common-mode/differential choke	At least 0.5 A DC without saturation	Select from conducted-emissions testing needs
CIN1	1	Input bulk capacitor	47–100 uF, 50 V low-ESR electrolytic	105 C preferred	Add 1 uF and 100 nF ceramics locally
RIN/CIN	AR	TVS damping/EMI network	Resistor, ferrite and capacitors	Datasheet/test determined	Do not populate an unverified high-energy LC network without damping review

Buck Regulator Support Components

Table

Ref. group	Qty	Function	Preliminary selection	Notes
LBUCK	1	Buck inductor	Value from LM5013 design calculation, Isat above peak current	Use shielded inductor and account for ripple/current/temperature
DBUCK	1	Catch diode if required	Schottky, voltage rating matched to input	LM5013 topology/datasheet dependent
C5V	2–4	5 V output capacitors	Effective 44–100 uF total plus 100 nF	Double nominal ceramic value for DC-bias derating
RFB1/RFB2	2	5 V feedback divider	1% resistors	Calculate directly from chosen regulator reference voltage
CSS/COMP	AR	Soft-start/compensation	Datasheet-derived	Do not copy between regulator families

Logic, Reset and Decoupling

Table

Ref. group	Qty	Function	Preferred part / class	Notes
CDEC	12–20	IC decoupling	100 nF, X7R, 16 V, 0603	One close to every supply pin/group
CBULK3V3	2	3.3 V bulk	10 uF, X7R, 10 V, 0805/1206	Verify effective capacitance at bias
RNRST	1	MCU reset pull-up	10 kohm	Pair with optional 100 nF reset capacitor if ST guidance permits
SW1	1	Reset switch	SMD momentary tactile	Pull NRST low
SW2	1	Pair/commission switch	SMD momentary tactile	Firmware-defined input with debounce
JTAG1	1	SWD connector	Tag-Connect TC2030 footprint or 10-pin Cortex header	Include SWDIO, SWCLK, NRST, 3.3 V and grounds
JDBG1	1	UART diagnostics	1x4 2.54 mm header/test pads	3.3 V logic only; label TX/RX/GND/VREF

Relay Drivers and Indicators

Table

Ref. group	Qty	Function	Preferred part / class	Notes
DCOIL1–10	10	Flyback suppression	1N4148W or 1N400x-class diode	May be omitted where ULN2803 clamp is used correctly; communications drivers still need clamps
QCOMM1–2	2	Communications relay low-side driver	2N7002 or AO3400A	Logic-level N-MOSFET with adequate VDS/current margin
RG1–10	10	MOSFET gate resistor	47–220 ohm	Only for discrete MOSFET channels
RPD1–10	10	Default-off pull-down	47–100 kohm	Mandatory on relay-driver gates/bases
LED1–14	14 max	Power/status/channel indication	Green/amber/red 0603 or 0805 LEDs	Keep typical current around 1–2 mA each
RLED	14 max	LED current limiting	Approximately 1–3.3 kohm depending on rail/color	Calculate per LED forward voltage and desired current

Field and RF Connectors

Table

Ref. group	Qty	Function	Preferred part / class	Notes
J2–J11	10	Relay contact terminal	3-position 5.08 mm pluggable terminal	Label NC-COM-NO on PCB and enclosure documentation
J12	1	PCB RF connector	U.FL/I-PEX MHF-compatible 50-ohm connector	Use manufacturer land pattern and qualified pigtail
A1	1	External antenna	EU868 50-ohm enclosure-mount antenna	Gain and cable type must be allowed by module certification/integration rules
CMC/ESD-RF	Optional	RF connector protection	Ultra-low-capacitance RF ESD device	Only if insertion loss and RF layout are acceptable

Timing Components for External Watchdog

Table

Ref. group	Qty	Function	Preliminary value	Notes
RWD1–2	2	Monostable timing resistor	Sized for approximately 1–3 s timeout	Use datasheet equation and tolerance limits
CWD1–2	2	Monostable timing capacitor	Stable low-leakage capacitor	Avoid relying on a 30 s analog timeout; firmware decides link health, hardware verifies continued execution
RWD-BIAS	AR	Defined startup state	10–100 kohm range	Ensure communications relays are de-energized until valid service pulses occur

Mechanical and Assembly Items

Table

Item	Qty	Recommendation	Notes
PCB	1	Four-layer, 1.6 mm FR-4, 1 oz copper	Approximate 160–220 mm x 100–140 mm pending enclosure and connector layout
Enclosure	1	DIN-rail control enclosure, flame-retardant, IP20 or better	Size after terminal and antenna placement
SMA bulkhead pigtail	1	U.FL-to-SMA female bulkhead, 50 ohm	Mechanically retained by enclosure
Mounting hardware	4+	M3 standoffs/screws or enclosure PCB clips	Maintain clearances below PCB
Terminal plugs	11	Matching pluggable terminal bodies	One 2-way input and ten 3-way relay outputs

Preliminary Cost and Sourcing Notes

Relays, pluggable terminals, radio module, enclosure, and assembly labor are expected to dominate unit cost.
Ten separate 3-position pluggable terminals significantly increase board width and cost but provide the clearest serviceable field interface.
Use distributor-authorized supply for the radio module and relays to preserve traceability.
Do not purchase the antenna until the exact radio module SKU and its permitted antenna-gain/integration conditions are confirmed.
At least one second-source strategy should be qualified for the buck converter, LDO, terminal family, and relay family before production.

Items Requiring Final Selection Before Schematic Release

Exact RAK3172 regional/orderable SKU, firmware model, certification evidence, and RF pin/connector arrangement.
Exact Omron G5V-1 5 V relay suffix and verified footprint/contact life.
Exact buck regulator implementation and calculated inductor/capacitor/feedback values.
Input surge environment and coordinated fuse/TVS/reverse-polarity network.
Exact Siemens S7-1500 digital-input module and field wiring convention.
Enclosure dimensions, antenna bulkhead position, ambient temperature, and terminal orientation.
Whether direct MCU GPIO or MCP23017 expansion is preferred after final pin allocation.

Status and Use
Recommended Core Components
Power Input and Protection
Buck Regulator Support Components
Logic, Reset and Decoupling
Relay Drivers and Indicators
Field and RF Connectors
Timing Components for External Watchdog
Mechanical and Assembly Items
Preliminary Cost and Sourcing Notes
Items Requiring Final Selection Before Schematic Release