OpenEnergyMonitor emonPi Energy Monitor

This lab introduces electrical power measurement, data acquisition, and IoT telemetry using the open-source OpenEnergyMonitor emonPi hardware platform. Working with an ATmega328P-based shield interfaced to a Raspberry Pi single-board computer, students sample AC voltage waveforms via an isolated step-down transformer and alternating currents using non-invasive current transformers. Students learn analog signal conditioning principles such as DC biasing, burden resistor selection, and RMS calculation algorithms to determine real power, apparent power, and power factor. In addition to electrical monitoring, students configure Dallas 1-Wire digital temperature sensors, handle pulse counting inputs, and establish serial and sub-GHz wireless telemetry. Through the local Linux-based Emoncms web server, Mosquitto MQTT broker, and time-series database stack, students analyze building energy consumption, evaluate renewable generation, and calibrate sensor telemetry for smart energy systems.

energy monitoring power measurement current transformer CT sensor AC voltage sensing real power apparent power power factor Raspberry Pi ATmega328P microcontroller Internet of Things IoT Emoncms 1-Wire DS18B20 temperature sensor MQTT embedded systems data acquisition smart meter

Uploaded by demo on 2026-09-03 · ready · Electronics · Original source ↗

Files: emonPi_V1.5.brd · emonPi_V1.5_brd_values.pdf · emonPi_V1.5_sch.pdf · emonSD_download_page.html · emoncms_README.md · emonpi_README.md · emonpi_V1.5_hardware_readme.md

Readiness checks

  • complete 2026-09-03 01:19 🛡 Cybersecurity: Do not place on an open network · 2 findings 62 searches · 4 pages · $0.54
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Latest report — 2026-09-03 01:19

Readiness: OpenEnergyMonitor emonPi Energy Monitor

Verdict: Ready with caveats · 2026-09-03 · est. parts cost $105–$160 ($35 shield only) Cybersecurity — software & network: Do not place on an open network

All essential components are procurable today. The sub-GHz radio module (HopeRF RFM69CW) is not stocked at US tier-1 franchised distributors (DigiKey/Mouser) and must be ordered from European or specialist distributors (such as TME or LowPowerLab), where stock is plentiful. Several generic passive, protection, and connector components (0.1 µF and 1 µF 0603 MLCCs, the 1812 PTC resettable fuse, and the Multicomp DC barrel jack) are discontinued or obsolete under the snapshot's exact part numbers, but all have verified, pin- and footprint-identical drop-in substitutes available in volume from DigiKey. This is the cold check; it establishes the baseline for future drift monitoring.

Action required

Part Problem Recommended action
HopeRF RFM69CW-868S2 / RFM69CW-433S2 Not stocked by US tier-1 franchised distributors (DigiKey, Mouser). Procure directly from European or specialist distributors (TME stocks RFM69CW-868S2; LowPowerLab stocks 868/915 MHz). Do not substitute RFM69HCW due to footprint incompatibility.
Murata GRM188R71E104KA01D (C1, C2, C5, C6, C7) Obsolete; 0 stock at authorized distributors. Substitute KEMET C0603C104K3RACTU (0.1 µF, 25V, X7R, 0603).
Murata GRM188R61A106KE69D (C3, C4, C10) Zero distributor inventory; 19-week factory lead time. Substitute TDK C1608X5R1A106K080AC (10 µF, 10V, X5R, 0603).
Murata GRM188R71C105KA12D (C14, C15) Obsolete; 0 stock at authorized distributors. Substitute TDK C1608X7R1C105K080AC (1 µF, 16V, X7R, 0603).
Bourns MF-MSMF150-2 (F1) Obsolete; residual stock critically low (105 at DigiKey). Substitute Bourns MF-MSMF150/24X-2 (1.5A hold, 24V max, 1812).
Multicomp SPC4077 / SPC-4077 (J4) Obsolete and unlisted across distributors. Substitute Same Sky PJ-002AH (2.1 mm ID × 5.5 mm OD barrel jack, THT).
Wurth Elektronik 651005161859 (U$7) Part number unlisted at distributors. Procure snapshot alternate Amphenol 10033526-N3212LF (Mini-USB Type B SMD).
Kycon STX-3100-5N (CT1, CT2) Zero inventory at DigiKey (18-week factory lead time). Order from Mouser (1,010 units in stock).

Cybersecurity — software & network

Do not place on an open network — The system images ship with published default credentials across multiple network services and legacy releases run an end-of-life operating system.

Component Version How known Support status
Debian bookworm inferred (inferred from emonSD-01Feb24 base OS documentation in snapshot) extended/LTS support only until 2028-06-30
Debian bullseye inferred (inferred from legacy emonSD-20Nov23 base OS documentation in snapshot) unsupported since 2024-08-14
emonSD 01Feb24 inferred (inferred from lab snapshot documentation) —
EmonScripts v1.7.10 inferred (inferred from emonSD-01Feb24 documentation in snapshot) —
emonPi AVR Firmware not determined not determined —
emoncms/emoncms 11.4.11 inferred (inferred from emonSD-01Feb24 documentation in snapshot) unsupported since 2024-08-14
Apache HTTP Server 2.4.57 inferred (inferred from emonSD-01Feb24 documentation in snapshot) —
Mosquitto MQTT 2.0.11 inferred (inferred from emonSD-01Feb24 documentation in snapshot) —
Redis 7.0.11 inferred (inferred from emonSD-01Feb24 documentation in snapshot) —
MariaDB 10.11.3-MariaDB inferred (inferred from emonSD-01Feb24 documentation in snapshot) —
PHP 8.1.27 inferred (inferred from emonSD-01Feb24 documentation in snapshot) —
Component Finding Severity Fix available?
Debian The legacy emonSD-20Nov23 image runs Debian 11 Bullseye, which reached end of life on 2026-08-31 and receives no further security updates. posture No — requires platform migration
emonSD The system images ship with published default credentials for the Emoncms web interface, MQTT broker, Wi-Fi access point, and SSH. posture Mitigation only — change all default passwords for Emoncms, MQTT, Wi-Fi AP, and SSH before connecting the device to any network

What this means for your lab

Anyone on the same local network can access the emonPi web dashboard and MQTT broker using published default credentials, allowing unauthorized users to observe energy telemetry and modify system configurations. If SSH access is enabled or the initial setup Wi-Fi access point is active, unauthorized actors can obtain complete shell control over the Raspberry Pi using default login passwords. Before placing this device on any network, instructors must change all default credentials for Emoncms, SSH, MQTT, and Wi-Fi, verify that the unit runs a currently supported operating system release rather than legacy Debian Bullseye, and isolate the system on a restricted network segment.

Not checked

  • emonPi AVR Firmware: Custom microcontroller firmware and Arduino libraries without a vulnerability database; version not determined.
  • EmonScripts: Vendor deployment scripts repository without a public vulnerability database.
  • System packages (Apache, MariaDB, Redis, Mosquitto MQTT, PHP): Operating system distribution packages not checked against a package advisory database in this lookup.
  • Emoncms submodules: Application submodules (Emonhub, Dashboard, Device, Graph, etc.) lack individual vulnerability database entries.

Parts

1. Integrated Circuits and Active Semiconductors

Part Spec/Package Status Stock Price Source
Microchip ATMEGA328P-AU 8-bit AVR MCU, 32 KB Flash, 16 MHz, TQFP-32 Active 29,655 $2.66 DigiKey
onsemi CAT24C32WI-GT3 32 Kbit I2C Serial EEPROM, SOIC-8 Active 2,645 $0.47 DigiKey
Microchip MCP1700T-3302E/TT LDO Regulator, 3.3V, 250 mA, SOT-23-3 Active 67,588 $0.51 DigiKey
HopeRF RFM69CW-868S2 Sub-GHz ISM RF Transceiver, 14-pad SMD edge castellated Active 423 ~$3.11 (£2.36) TME
onsemi 1N4148WT (D1, D2, D3) Switching Diode, 75V, 200 mA, SOD-523F Active 8,000 $0.17 DigiKey
Kingbright APT2012EC (LED) Red SMD LED, 625 nm, 0805 SMD Active 111,551 $0.20 DigiKey

2. Passive Components

Part Spec/Package Status Stock Price Source
Yageo RC0603FR-07470KL (R11, R12, R21, R23, R25, R27) Resistor, 470 kΩ, 1%, 0.1W, 0603 SMD Active 419,648 $0.10 DigiKey
Yageo RC0603FR-071KL (R2, R3, R4, R6, R10) Resistor, 1 kΩ, 1%, 0.1W, 0603 SMD Active 4,091,047 $0.10 DigiKey
Yageo RC0603FR-073K9L (R8, R9) Resistor, 3.9 kΩ, 1%, 0.1W, 0603 SMD Active 520,629 $0.10 DigiKey
Yageo RC0603FR-0710KL (R7, R14) Resistor, 10 kΩ, 1%, 0.1W, 0603 SMD Active 3,367,404 $0.10 DigiKey
Yageo RC0603FR-07120KL (R1, R13) Resistor, 120 kΩ, 1%, 0.1W, 0603 SMD Active 112,407 $0.10 DigiKey
Yageo RC0603JR-070RL (R29, R30) Resistor, 0 Ω Jumper, 0603 SMD Active 8,086,253 $0.10 DigiKey
Vishay Dale CRCW120622R0FKEA (R17, R28) Resistor, 22 Ω, 1%, 0.25W, 1206 SMD (burden option) Active 14,009 $0.11 DigiKey
TE Connectivity LR1F22R (R22, R26) Resistor, 22 Ω, 1%, 0.6W, Axial THT (burden option) Active 11,252 $0.10 DigiKey
Yageo RC0603FR-074K7L (R24) Resistor, 4.7 kΩ, 1%, 0.1W, 0603 SMD (1-Wire option) Active 1,596,664 $0.10 DigiKey
TE Connectivity LR1F4K7 (R5) Resistor, 4.7 kΩ, 1%, 0.6W, Axial THT (1-Wire option) Active 5,216 $0.12 DigiKey
Murata GRM188R71E104KA01D (C1, C2, C5, C6, C7) Capacitor, 0.1 µF, 25V, X7R, 0603 SMD Obsolete 0 — DigiKey
Murata GRM188R61A106KE69D (C3, C4, C10) Capacitor, 10 µF, 10V, X5R, 0603 SMD Active 0 — DigiKey
Murata GRM188R71C105KA12D (C14, C15) Capacitor, 1 µF, 16V, X7R, 0603 SMD Obsolete 0 — DigiKey
TDK CGA3E1X7R1E105K080AC (C8) Capacitor, 1 µF, 25V, X7R, 0603 SMD Active 1,400,622 $0.17 DigiKey
Murata GRM1885C1H220JA01D (C9, C11) Capacitor, 22 pF, 50V, C0G/NP0, 0603 SMD Not For New Designs 107,791 $0.11 DigiKey
Bourns MF-MSMF150-2 (F1) Resettable PTC Fuse, 1.5A hold, 6V max, 1812 SMD Obsolete 105 $0.71 DigiKey
Abracon ABLS-16.000MHZ-B4-T (Q1) Crystal Resonator, 16.000 MHz, 18 pF, HC49/US SMD Active 13,646 $0.24 DigiKey

3. Connectors, Switches, and Controls

Part Spec/Package Status Stock Price Source
Omron / Aratas B3F-3150 (S1) Tactile Push Button, SPST-NO, extended actuator, THT Active 10,136 $0.54 DigiKey
Kycon STX-3100-5N (CT1, CT2) 3.5 mm Stereo Audio Jack, 5-pin switched, THT R/A Active 1,010 $1.60 Mouser
Phoenix Contact 1984617 (J1, J2, J3) Terminal Block, 2-pos, 3.5 mm pitch, screw clamp, THT Active 48,088 $0.59 DigiKey
Multicomp SPC4077 / SPC-4077 (J4) DC Power Barrel Jack, 2.1 mm ID × 5.5 mm OD, THT Obsolete 0 — Unlisted
Amphenol RF 132136 (J$1) SMA Female RF Connector, 50 Ω, edge-mount Active 6,497 $11.53 DigiKey
Wurth 651005161859 / Amphenol 10033526-N3212LF (U$7) Mini-USB Type B Receptacle, 5-pin female SMD R/A Active 9,947 $0.80 DigiKey
Stewart Connector SS-6488-NF (U$13) RJ45 8P8C Modular Jack, unshielded, THT Active 27,211 $1.97 DigiKey
Raspberry Pi 40-Pin GPIO Stacking Header (X1/X4) 2x20 Female Socket Header, 2.54 mm pitch, extra tall Active In stock $0.63 DigiKey
Harwin M20-9980346 (ISP1) Pin Header, 2x3 male, 2.54 mm pitch, vertical THT Active 51,391 $0.25 DigiKey
Harwin M20-9990446 (JP2) Pin Header, 1x4 male, 2.54 mm pitch, vertical THT Active 36,844 $0.17 DigiKey
Harwin M20-9990646 (JP3) Pin Header, 1x6 male, 2.54 mm pitch, vertical THT Active 18,505 $0.25 DigiKey
Harwin M20-9990246 (JP4, JP5) Pin Header, 1x2 male, 2.54 mm pitch, vertical THT Active 184,254 $0.10 DigiKey

4. Unpopulated Options, Footprint Alternatives, and Mechanical Features

Part Spec/Package Status Stock Price Source
U1_MLF ATmega328P co-footprint, MLF-32 / QFN-32 unpopulated — — —
OOK 433 MHz OOK transmitter footprint, 4-pin 0.1" SIP unpopulated — — —
ANT1, ANT2 Wire antenna direct solder pads, PAD-01 PCB feature — — —
TP1, TP2, TP3 Production test pads, P1-13 PCB feature — — —
U$1, U$3, U$4, U$5 Optical fiducial marks, 1.0 mm bare copper PCB feature — — —
U$9 Standoff mounting hole for M2.5 hardware PCB feature — — —
LOGO1 Open Source Hardware graphic logo PCB feature — — —

5. Required External Off-Board Hardware

Part Spec/Package Status Stock Price Source
Raspberry Pi 4 Model B (or 3B+) Single-Board Computer, 40-pin GPIO, quad-core ARM Active In stock $35.00 CanaKit
YHDC SCT-013-000 Current Transformer, 100A:50mA split-core, 3.5mm plug Active In stock $9.50 RocketController
Ideal Power 77DE-06-09 (EU) / 77DB-06-09 (UK) AC-AC Step-Down Adapter, 9V AC 670 mA, 2.1mm plug Active 85 $8.78 DigiKey
Olimex SNS-TMP-DS18B20-MAXIM Dallas DS18B20 digital temperature sensor probe Active 256 $5.25 DigiKey
Inland 1602 I2C Display Module 16x2 Character LCD with PCF8574 I2C daughterboard Active In stock $4.99 Micro Center
U.S. Converters 5VDC Mini USB Power Supply 5V DC 2.0A–2.5A Power Supply Adapter, Mini-USB Active In stock $10.50 U.S. Converters

Substitutes

For part Substitute Differences Verified Judgment
Murata GRM188R71E104KA01D (0.1 µF, 25V, X7R, 0603) KEMET C0603C104K3RACTU 0.1 µF (100 nF), 25V (meets ≥ 16V snapshot constraint, matches original 25V), X7R dielectric (-55°C to +125°C), ±10% tolerance, 0603 SMD. package + dimensions (DigiKey parametrics: 0603, 1.60 mm × 0.80 mm MLCC), capacitance, voltage rating, dielectric grade Acceptable
Murata GRM188R61A106KE69D (10 µF, 10V, X5R, 0603) TDK C1608X5R1A106K080AC 10 µF, 10V (meets ≥ 10V snapshot constraint), X5R dielectric (-55°C to +85°C), ±10% tolerance, 0603 SMD. package + dimensions (DigiKey parametrics: 0603, 1.60 mm × 0.80 mm MLCC), capacitance, voltage rating, dielectric grade Acceptable
Murata GRM188R71C105KA12D (1 µF, 16V, X7R, 0603) TDK C1608X7R1C105K080AC 1 µF, 16V (meets ≥ 16V snapshot constraint), X7R dielectric (-55°C to +125°C), ±10% tolerance, 0603 SMD. package + dimensions (DigiKey parametrics: 0603, 1.60 mm × 0.80 mm MLCC), capacitance, voltage rating, dielectric grade Acceptable
Murata GRM1885C1H220JA01D (22 pF, 50V, C0G, 0603) KEMET C0603C220J5GACTU 22 pF, 50V, C0G/NP0 dielectric, ±5% tolerance, 0603 SMD. Active replacement for NFND Murata part. package 0603, capacitance 22 pF, voltage 50V, C0G dielectric Acceptable
Bourns MF-MSMF150-2 (PTC fuse, 1.5A, 6V, 1812) Bourns MF-MSMF150/24X-2 1.5A hold, 3.0A trip; maximum voltage 24V (exceeds original 6V, meets ≥ 6V constraint); resistance 30 mΩ min, 120 mΩ max post-trip; 1812 Concave SMD package. package + dimensions (DigiKey parametrics: 1812 Concave, 4.55 mm × 3.24 mm), hold/trip current ratings, resistance parameters, voltage rating (24V ≥ 6V) Acceptable
Multicomp SPC4077 (2.1 mm ID × 5.5 mm OD DC jack) Same Sky PJ-002AH 2.1 mm center pin ID × 5.5 mm OD barrel jack, through-hole right-angle mounting, 2 conductors, 3 contacts (shunt switch), rated 24V DC / 5A (exceeds 9V AC requirement). barrel pin dimensions (2.1 mm / 5.5 mm), mounting type (through-hole, right angle), current/voltage ratings Acceptable
HopeRF RFM69CW-868S2 (14-pad SMD transceiver) HopeRF RFM69HCW-868S2 Higher RF output (+20 dBm vs +13 dBm), but footprint is LCC-16 (16-pad, incompatible pinout) vs 14-pad edge-castellated footprint on the PCB. not stated Disqualified

Always verify any substitute against its datasheet and PCB footprint before ordering.

Other dependencies

  • PCB Fabrication: Standard 2-layer FR4 PCB, 99.10 mm × 76.00 mm, 1.6 mm board thickness, 1 oz (35 µm) outer copper, minimum 8 mil trace / 8 mil clearance, white silkscreen over solder mask, lead-free HASL or ENIG finish with 4 optical fiducials. Status: Readily fabricable.
  • Hardware Schematic and Board Design Files (https://github.com/openenergymonitor/emonpi/tree/master/hardware): External repository containing Gerber and CAD files. Status: not checked.
  • OS Image Downloads Mirror (https://openenergymonitor.org/files/emonSD-01Feb24.zip): External file download host. Status: not checked.
  • System Provisioning Scripts Link (https://github.com/openenergymonitor/EmonScripts): External repository link. Status: not checked.
  • Emoncms Application Repository Link (https://github.com/emoncms/emoncms): External repository link. Status: not checked.
  • OpenEnergyMonitor Documentation Server (https://docs.openenergymonitor.org/): External documentation portal. Status: not checked.

Watch list

  • HopeRF RFM69CW Transceiver Module: Completely unstocked across US tier-1 franchised catalog distributors (DigiKey, Mouser, Newark). Sourcing is dependent on European specialist distributors (TME) or hobby vendors (LowPowerLab). If TME inventory drops, procurement lead times and supply chain friction will increase.
  • Obsolete Passive and Protection Components: Murata 0603 MLCCs (0.1 µF, 1 µF) and the original Bourns 1812 PTC fuse (MF-MSMF150-2) are discontinued. Active substitute part numbers must be transitioned into ordering workflows.
  • Kycon STX-3100-5N Audio Jacks: DigiKey shows zero inventory with an 18-week lead time, leaving catalog stock reliant on Mouser.
  • Ideal Power AC-AC Adapters: Factory-terminated 9V AC unrectified reference adapters (77DE-06-09 / 77DB-06-09) have limited distributor inventory (85 units at DigiKey).
Snapshot What the lab depended on when it was uploaded — the baseline the readiness checks research against.

This snapshot documents the hardware, software, and fabrication dependencies for the OpenEnergyMonitor emonPi Energy Monitor (Hardware Revision V1.5, dated January 2015).

The emonPi V1.5 is an open-source energy, temperature, and environmental monitoring shield designed to mount directly onto a 40-pin Raspberry Pi single-board computer (such as Raspberry Pi 2B, 3B, 3B+, 4B, or Zero 2 W). The shield features an onboard Atmel/Microchip ATmega328P 8-bit microcontroller running at 16 MHz that samples analog signals from two current transformers (CT1, CT2) and one 9V AC-AC voltage reference transformer (J4). The system logic and microcontroller operate entirely at 3.3V DC, regulated on-board by an MCP1700 low-dropout regulator from a 5V DC rail supplied either by an onboard Mini-USB receptacle or the Raspberry Pi GPIO bus. Communication between the microcontroller and the Raspberry Pi occurs via UART (/dev/ttyAMA0) or SPI, with sub-GHz ISM radio telemetry handled by an onboard HopeRF RFM12B or RFM69CW transceiver module.

Bill of Materials

1. Integrated Circuits and Active Semiconductors

  • U1_TQFP — 8-bit AVR Microcontroller, 32 KB Flash

    • Manufacturer / Part Number: Microchip / Atmel ATMEGA328P-AU
    • Quantity: 1
    • Package / Footprint: TQFP-32 (TQFP32-08)
    • Electrical constraints: Supply voltage 3.3V DC, external 16 MHz clock.
    • Note: Co-located with footprint U1_MLF. ATmega328P is operated at 3.3V with a 16 MHz crystal (technically exceeding the 13.3 MHz nominal operating limit at 3.3V per Microchip datasheet specifications, but standard for the OpenEnergyMonitor platform). Requires at least 32 KB flash memory to hold the emonPi firmware.
    • Sourcing plan: distributor lookup: ATMEGA328P-AU

  • U1 — 32 Kbit I2C Serial CMOS EEPROM (Raspberry Pi HAT ID)

    • Manufacturer / Part Number: Onsemi CAT24C32WI-GT3
    • Quantity: 1
    • Package / Footprint: SOIC-8 (SO08)
    • Electrical constraints: Supply voltage 3.3V DC, I2C address lines configured via pull-downs.
    • Substitution latitude: Pin-compatible 32-Kbit I2C EEPROMs (such as Microchip 24LC32A or ST M24C32) in SOIC-8 operating at 3.3V can be substituted if programmed with the Raspberry Pi HAT ID tree blob.
    • Sourcing plan: distributor lookup: CAT24C32WI-GT3

  • U$8 — Low-Dropout Voltage Regulator, 3.3V, 250 mA

    • Manufacturer / Part Number: Microchip MCP1700T-3302E/TT
    • Quantity: 1
    • Package / Footprint: SOT-23-3 (SOT95P237X112-3N)
    • Electrical constraints: Input voltage 5.0V DC (from USB/Pi), output 3.3V DC fixed, 250 mA max current, ultra-low quiescent current (approx 1.6 µA).
    • Substitution latitude: Any LDO regulator in SOT-23 pinout (1: GND, 2: VOUT, 3: VIN) capable of delivering ≥ 250 mA at 3.3V with an input rating ≥ 6V.
    • Sourcing plan: distributor lookup: MCP1700T-3302E/TT

  • U$14 — Sub-GHz ISM RF Transceiver Module

    • Manufacturer / Part Number: HopeRF RFM69CW (or RFM12B)
    • Quantity: 1
    • Package / Footprint: RFM12B / RFM69CW SMD edge-castellated footprint (JeeParts library, 14-pad SMD)
    • Electrical constraints: Supply voltage 3.3V DC, SPI bus interface, operating frequency 433 MHz or 868 MHz depending on geographic region.
    • Substitution latitude: Must match the HopeRF pinout and register command set expected by the emonLib / JeeLib AVR firmware.
    • Sourcing plan: distributor lookup: RFM69CW-868S2 or RFM69CW-433S2

  • D1, D2, D3 — Small Signal Switching / Protection Diodes

    • Manufacturer / Part Number: Unspecified (SOD-523 small signal diodes)
    • Quantity: 3
    • Package / Footprint: SOD-523
    • Electrical constraints: Reverse voltage VR ≥ 20V, forward current IF ≥ 100 mA.
    • Substitution latitude: Standard small-signal switching or Schottky barrier diodes (e.g. 1N4148WT or BAT54WS).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): 1N4148WT

  • LED — Status / Activity Indicator LED, Red

    • Manufacturer / Part Number: Unspecified 0805 Surface Mount LED
    • Quantity: 1
    • Package / Footprint: 0805 SMD (CHIPLED_0805)
    • Electrical constraints: Forward current driven through 1 kΩ resistor (R10) from 3.3V logic (approx 1.5–2 mA).
    • Substitution latitude: Any standard 0805 red SMD LED.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Kingbright APT2012EC

2. Passive Components

  • Resistors, 470 kΩ, 0603 SMD, 1%

    • Reference designators: R11, R12, R21, R23, R25, R27
    • Quantity: 6
    • Package / Footprint: 0603 SMD (R0603)
    • Electrical constraints: 470 kΩ, 1% tolerance, 0.1W, mid-rail VCC/2 bias dividers for AC voltage and CT analog inputs.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RC0603FR-07470KL

  • Resistors, 1 kΩ, 0603 SMD, 1%

    • Reference designators: R2, R3, R4, R6, R10
    • Quantity: 5
    • Package / Footprint: 0603 SMD (R0603)
    • Electrical constraints: 1 kΩ, 0.1W, series protection and LED current limiting.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RC0603FR-071KL

  • Resistors, 3.9 kΩ, 0603 SMD, 1%

    • Reference designators: R8, R9
    • Quantity: 2
    • Package / Footprint: 0603 SMD (R0603)
    • Electrical constraints: 3.9 kΩ, 0.1W, I2C pull-up resistors for EEPROM ID bus.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RC0603FR-073K9L

  • Resistors, 10 kΩ, 0603 SMD, 1%

    • Reference designators: R7, R14
    • Quantity: 2
    • Package / Footprint: 0603 SMD (R0603)
    • Electrical constraints: 10 kΩ, 0.1W (R7 reset pull-up, R14 AC voltage divider low side).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RC0603FR-0710KL

  • Resistors, 120 kΩ, 0603 SMD, 1%

    • Reference designators: R1, R13
    • Quantity: 2
    • Package / Footprint: 0603 SMD (R0603)
    • Electrical constraints: 120 kΩ, 1% tolerance, 0.1W (R13 is the AC voltage divider high-side resistor).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RC0603FR-07120KL

  • Resistors, 0 Ω (Jumpers), 0603 SMD

    • Reference designators: R29, R30
    • Quantity: 2
    • Package / Footprint: 0603 SMD (R0603)
    • Electrical constraints: 0 Ω jumper links for selecting between SMA antenna connector and wire antenna pad.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RC0603JR-070RL

  • Resistors, 22 Ω, 1206 SMD, 1% (CT Burden Resistors, SMD option)

    • Reference designators: R17, R28
    • Quantity: 2
    • Package / Footprint: 1206 SMD (R1206)
    • Electrical constraints: 22 Ω, 1% tolerance, ≥ 0.25W power rating. Burden resistors converting CT secondary current to voltage.
    • Note: Alternate co-footprints to through-hole axial resistors R22 and R26.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Vishay CRCW120622R0FKEA

  • Resistors, 22 Ω, Axial Through-Hole, 1% (CT Burden Resistors, THT option)

    • Reference designators: R22, R26
    • Quantity: 2
    • Package / Footprint: Axial 0204/7 (through-hole, 7.5 mm lead spacing)
    • Electrical constraints: 22 Ω, 1% tolerance, ≥ 0.25W.
    • Note: Alternate co-footprint for R17 and R28. Populate either SMD or THT, not both.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): TE Connectivity LR1F22R

  • Resistor, 4.7 kΩ, 0603 SMD, 1% (1-Wire Pull-up, SMD option)

    • Reference designator: R24
    • Quantity: 1
    • Package / Footprint: 0603 SMD (R0603)
    • Electrical constraints: 4.7 kΩ, 0.1W, pull-up for Dallas 1-Wire temperature bus.
    • Note: Alternate co-footprint to axial resistor R5.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Yageo RC0603FR-074K7L

  • Resistor, 4.7 kΩ, Axial Through-Hole, 1% (1-Wire Pull-up, THT option)

    • Reference designator: R5
    • Quantity: 1
    • Package / Footprint: Axial 0204/7 (through-hole, 7.5 mm lead spacing)
    • Electrical constraints: 4.7 kΩ, 0.25W.
    • Note: Alternate co-footprint to R24.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): TE Connectivity LR1F4K7

  • Capacitors, Ceramic, 0.1 µF (100 nF), 0603 SMD

    • Reference designators: C1, C2, C5, C6, C7
    • Quantity: 5
    • Package / Footprint: 0603 SMD (C0603)
    • Electrical constraints: 0.1 µF (100 nF), X7R or X5R dielectric, rated ≥ 16V. Decoupling and AC coupling for reset.
    • Note: Schematic lists C1, C6, C7 as "0.1uF" and C2, C5 as "100nF"; these are identical 100 nF parts.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Murata GRM188R71E104KA01D

  • Capacitors, Ceramic, 10 µF, 0603 SMD

    • Reference designators: C3, C4, C10
    • Quantity: 3
    • Package / Footprint: 0603 SMD (C0603)
    • Electrical constraints: 10 µF, X5R or X7R dielectric, rated ≥ 10V (typically 10V or 16V). DC bias stabilization on analog mid-rail reference nodes.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Murata GRM188R61A106KE69D

  • Capacitors, Ceramic, 1 µF, 0603 SMD

    • Reference designators: C14, C15
    • Quantity: 2
    • Package / Footprint: 0603 SMD (C0603)
    • Electrical constraints: 1 µF, X7R dielectric, rated ≥ 16V. Input and output decoupling for MCP1700 LDO regulator.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Murata GRM188R71C105KA12D

  • Capacitor, Ceramic, 1 µF, 25V, 0603 SMD

    • Reference designator: C8
    • Quantity: 1
    • Package / Footprint: 0603 SMD (C0603)
    • Electrical constraints: 1 µF, X7R dielectric, rated ≥ 25V. AC voltage input coupling capacitor.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): TDK CGA3E1X7R1E105K080AC

  • Capacitors, Ceramic, 22 pF, 0603 SMD

    • Reference designators: C9, C11
    • Quantity: 2
    • Package / Footprint: 0603 SMD (C0603)
    • Electrical constraints: 22 pF, C0G/NP0 dielectric, rated ≥ 25V. Crystal load capacitors for 16 MHz resonator.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Murata GRM1885C1H220JA01D

  • Resettable Fuse, PTC, 1.5A, 1812 SMD

    • Reference designator: F1
    • Quantity: 1
    • Package / Footprint: 1812 SMD (PTC1812L)
    • Electrical constraints: Hold current 1.5A, trip current approx 3.0A, maximum voltage Vmax ≥ 6V. Overcurrent protection on the 5V power input.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Bourns MF-MSMF150-2

  • Crystal Resonator, 16 MHz, HC49/US

    • Reference designator: Q1
    • Quantity: 1
    • Package / Footprint: HC49/US SMD (HC49UP)
    • Electrical constraints: Frequency 16.000 MHz, load capacitance 18 pF, tolerance ±30 ppm.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Abracon ABLS-16.000MHZ-B4-T

3. Connectors, Switches, and Controls

  • S1 — Tactile Push Button Switch

    • Manufacturer / Part Number: Omron B3F-31xx series (e.g. B3F-3150 / B3F-3122)
    • Quantity: 1
    • Package / Footprint: 6x6 mm through-hole tactile switch with extended round actuator (B3F-31XX)
    • Electrical constraints: Single Pole Single Throw (SPST-NO), rated 12V DC, 50 mA.
    • User-operated control: Yes. This is an external user-facing control operated during lab usage to scroll through LCD display pages, initiate graceful Raspberry Pi shutdown, and enable SSH access (long press for 5 seconds). The actuator must extend sufficiently through the enclosure front panel.
    • Sourcing plan: distributor lookup: Omron B3F-3150

  • CT1, CT2 — 3.5 mm Stereo Audio Jacks (Current Transformer Inputs)

    • Manufacturer / Part Number: Adafruit STX3100 footprint (standard 3.5mm stereo switched phone jack)
    • Quantity: 2
    • Package / Footprint: 3.5mm through-hole jack (STX3100)
    • Electrical constraints: Mates with standard 3.5mm 3-pole TRS / stereo audio plugs from YHDC SCT-013 current transformer sensors.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Kycon STX-3100-5N or CUI Devices SJ1-3515-SMT

  • J1, J2, J3 — 2-Pin 3.5 mm Pitch Screw Terminal Blocks

    • Manufacturer / Part Number: Adafruit 1X2-3.5MM terminal block footprint
    • Quantity: 3
    • Package / Footprint: 2-position through-hole terminal block, 3.5 mm pin pitch
    • Electrical constraints: Rated ≥ 100V, ≥ 2A. Used for pulse counter input and off-board 1-Wire temperature sensor wiring.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Phoenix Contact 1984617

  • J4 — 2.1 mm DC Power Barrel Jack (AC Voltage Sensing Input)

    • Manufacturer / Part Number: Multicomp SPC4077 / SPC-4077
    • Quantity: 1
    • Package / Footprint: 2.1 mm ID x 5.5 mm OD center pin through-hole barrel jack (SPC4077)
    • Electrical constraints: Input for 9V AC-AC step-down voltage reference transformer (unrectified AC).
    • Sourcing plan: distributor lookup: Multicomp SPC4077 (or CUI Devices PJ-002AH)

  • J$1 — SMA Female RF Connector, Edge-Mount

    • Manufacturer / Part Number: SparkFun SMA-EDGE footprint
    • Quantity: 1
    • Package / Footprint: Edge-mount SMA female connector for 1.6 mm PCB thickness
    • Electrical constraints: 50 Ω RF impedance, DC to 1 GHz.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Amphenol RF 132136

  • U$7 — Mini-USB Type B Receptacle (5V Power Input)

    • Manufacturer / Part Number: Ciseco USB-MINIB-CISECO footprint (standard 5-pin Mini-USB Type B SMD)
    • Quantity: 1
    • Package / Footprint: Mini-USB Type B female 5-pin surface-mount with through-hole shield retention posts
    • Electrical constraints: 5.0V DC power input rating ≥ 1.5A.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Wurth Elektronik 651005161859 or Amphenol 10033526-N3212LF

  • U$13 — RJ45 8P8C Modular Jack

    • Manufacturer / Part Number: SparkFun RJ45-8 footprint
    • Quantity: 1
    • Package / Footprint: 8P8C unshielded through-hole modular PCB jack
    • Electrical constraints: Connects DS18B20 1-Wire sensors (data, 5V/3.3V power, ground) and optical pulse sensor inputs.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Stewart Connector SS-6488-NF

  • X1 / X4 — Raspberry Pi 40-Pin GPIO Header (2x20 Pin Header, 2.54 mm pitch)

    • Manufacturer / Part Number: Raspberry Pi B+ 40-pin GPIO connector footprint (X1 is SMT: RASPI_SMT_GPIO_B+_PIN; X4 is THT: RASPI_GPIO_B+_PIN)
    • Quantity: 1 (populate either X1 or X4)
    • Package / Footprint: 2x20 female header socket, 2.54 mm (0.1") pitch, extra-tall stacking style recommended to clear Raspberry Pi USB and Ethernet jacks.
    • Sourcing plan: retail shopping search: Raspberry Pi 40-pin stacking header 2x20 2.54mm

  • ISP1 — AVR In-System Programming (ICSP) Header

    • Manufacturer / Part Number: SparkFun 2X3 footprint
    • Quantity: 1
    • Package / Footprint: 2x3 male pin header, 2.54 mm (0.1") pitch, through-hole.
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Harwin M20-9980346

  • JP2 — 4-Pin I2C Display Header

    • Manufacturer / Part Number: con-lstb MA06-1 footprint (4 pins used)
    • Quantity: 1
    • Package / Footprint: 1x4 male pin header, 2.54 mm pitch, through-hole (GND, 5V, SDA, SCL).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Harwin M20-9990446

  • JP3 — 6-Pin FTDI Serial Programming Header

    • Manufacturer / Part Number: SparkFun FTDI_BASIC footprint
    • Quantity: 1
    • Package / Footprint: 1x6 right-angle or straight male pin header, 2.54 mm pitch (DTR, RXI, TXO, VCC, CTS, GND).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Harwin M20-9990646

  • JP4, JP5 — 2-Pin Configuration Jumper Headers

    • Reference designators: JP4, JP5
    • Quantity: 2
    • Package / Footprint: 1x2 male pin header, 2.54 mm pitch (SparkFun 1X02)
    • Function: Hardware option selection (JP5 selects 1-Wire IRQ/pin mapping).
    • Sourcing plan: distributor lookup (representative example — sources give spec only): Harwin M20-9990246

4. Unpopulated Options, Footprint Alternatives, and Mechanical Features

  • U1_MLF — Microcontroller Alternative Footprint

    • Manufacturer / Part Number: Atmel ATMEGA168MLF (or ATMEGA328P-MU)
    • Quantity: 0 (optional co-footprint)
    • Package / Footprint: MLF-32 / QFN-32 (MLF32)
    • Note: Overlaid at identical board coordinates with U1_TQFP; left unpopulated in standard builds.

  • OOK — 433 MHz OOK RF Transmitter Module Footprint

    • Manufacturer / Part Number: SparkFun RF-LINK_TX footprint
    • Quantity: 0 (optional / unpopulated in standard build)
    • Package / Footprint: 4-pin 0.1" SIP header (GND, DATA, VCC, ANT)
    • Function: Footprint for low-cost 433 MHz amplitude-shift keyed transmitter module.

  • ANT1, ANT2 — Wire Antenna Solder Pads

    • Reference designators: ANT1, ANT2
    • Quantity: 2
    • Package / Footprint: Single through-hole solder pad (PAD-01)
    • Function: Direct solder connection for quarter-wave solid copper wire antenna (alternative to SMA connector J$1).

  • TP1, TP2, TP3 — Production Test Points

    • Reference designators: TP1, TP2, TP3
    • Quantity: 3
    • Package / Footprint: Surface copper test pad (P1-13)

  • U$1, U$3, U$4, U$5 — Optical Fiducial Marks

    • Reference designators: U$1, U$3, U$4, U$5
    • Quantity: 4
    • Package / Footprint: FIDUCIAL_1MM (bare circular fiducial dot on top copper layer, no component).

  • U$9 — PCB Standoff Mounting Hole

    • Reference designator: U$9
    • Quantity: 1
    • Package / Footprint: STAND-OFF (through-hole for M2.5 standoff / mounting screw).

  • LOGO1 — Open Source Hardware Logo

    • Reference designator: LOGO1
    • Quantity: 1
    • Package / Footprint: OSHW_10X200_NOTEXT (copper / silkscreen graphic).

5. Required External Off-Board Hardware

  • Single-Board Computer (Host Platform)

    • Model: Raspberry Pi 3B, 3B+, 4B, or Zero 2 W with 40-pin GPIO header.
    • Function: Runs the Linux operating system, emonHub serial bridge daemon, and local Emoncms server stack.
    • Sourcing plan: retail shopping search: Raspberry Pi 3B+ or Raspberry Pi 4 Model B

  • Current Transformer (CT) Sensors

    • Model: YHDC SCT-013-000 (100A:50mA non-invasive clip-on current transformer) terminated with 3.5mm stereo jack.
    • Quantity: Up to 2 (one for CT1, one for CT2).
    • Sourcing plan: retail shopping search: YHDC SCT-013-000 current transformer

  • AC-AC Voltage Reference Transformer

    • Model: Ideal Power 77DB-06-09 (UK), 77DE-06-09 (EU), or 77DA-06-09 (US), 9V AC nominal output, 2.1mm barrel connector.
    • Quantity: 1 (connects to J4).
    • Function: Provides galvanic isolation and an unrectified proportional voltage waveform for accurate real-power and RMS voltage calculations.
    • Sourcing plan: retail shopping search: Ideal Power 9V AC-AC adapter 77DB-06-09

  • 1-Wire Temperature Sensors

    • Model: Dallas / Maxim DS18B20 digital temperature probe encapsulated with cable terminated in RJ45 plug or bare leads.
    • Quantity: 1 or more (connects to U$13 or J1/J2/J3).
    • Sourcing plan: distributor lookup: DS18B20

  • I2C Character LCD Display

    • Model: 16x2 Character LCD display with PCF8574 I2C daughterboard (5V supply, 3.3V tolerant I2C lines).
    • Quantity: 1 (connects to JP2).
    • Function: Displays IP address, AC voltage, power readings, and safe-shutdown prompts.
    • Sourcing plan: retail shopping search: 1602 LCD I2C display module

  • 5V DC Power Supply

    • Model: 5V DC 2.0A or 2.5A power adapter with Mini-USB connector (or Micro-USB / USB-C powering the Raspberry Pi directly).
    • Sourcing plan: retail shopping search: 5V 2.5A Mini-USB power supply

Software and network dependencies

  • Operating System / Base Disk Images (emonSD)

    • Image distribution: emonSD pre-built Raspberry Pi OS Lite images available from the OpenEnergyMonitor documentation server (https://docs.openenergymonitor.org/emonsd/download.html).
    • Documented releases:
      • emonSD-10Mar26 (Raspberry Pi OS Lite 64-bit trixie base, release date 21 Apr 2026; MD5 d51d6b6c7c319a7ed8bf14ece35ca4a1).
      • emonSD-01Feb24 (Raspberry Pi OS Lite 32-bit Bookworm base, 2023-12-11; Linux kernel 6.1.0-rpi8-rpi-v8 #1 SMP PREEMPT Debian 1:6.1.73-1+rpt1; MD5 b64503d08704d1605a7ea23745f0a6fc).
      • emonSD-20Nov23 (Debian Raspberry Pi OS 64-bit Legacy Lite base, 2023-05-03; Linux kernel 6.1.21-v8+; MD5 ed9ecc0d8930d7f7422890e462b3020c).
      • emonSD-10Nov22 (Debian Raspberry Pi OS 32-bit Lite base, 2021-03-04; Linux kernel 5.15.76-v7l+; MD5 271d8d502e822e3703500a5762519c1d).
    • Version source: stated in documentation (emonSD_download_page.html).
    • Check plan: support-status lookup: Debian Bookworm (for emonSD-01Feb24) or Debian Bullseye (for emonSD-20Nov23).

  • Automated OS Provisioning Scripts

    • Tool name: EmonScripts
    • Repository: https://github.com/openenergymonitor/EmonScripts
    • Version: v1.7.10 (active on emonSD-01Feb24) and v1.6.25 (active on emonSD-20Nov23).
    • Version source: stated in documentation (emonSD_download_page.html).
    • Version pinning: Versions are tagged in git, but installation scripts perform unpinned package pulls (apt-get install without explicit package versions) from Debian/Raspbian repositories.
    • Check plan: not checkable: vendor git build script repo without public vulnerability database.

  • Microcontroller Firmware

    • Project: OpenEnergyMonitor emonPi Discrete Sampling / Continuous Monitoring AVR Firmware
    • Target: Atmel ATmega328P running at 16 MHz, 3.3V
    • Repository: https://github.com/openenergymonitor/emonpi (path hardware/firmware)
    • Build environment: Arduino IDE / avr-gcc / avrdude
    • Dependencies: JeeLib, emonLib (OpenEnergyMonitor energy monitoring library)
    • Version: not stated in hardware files.
    • Flashing path: Programmed in-situ via Raspberry Pi serial port /dev/ttyAMA0 using the avrdude-rpi bridge daemon or externally via FTDI header JP3 / ICSP header ISP1.
    • Check plan: not checkable: vendor custom embedded firmware.

  • Web Application and Logging Stack (Emoncms)

    • Repository: https://github.com/emoncms/emoncms.git
    • Version: low-write 11.4.11 (on emonSD-01Feb24) and low-write 11.4.2 (on emonSD-20Nov23), tracking git branch stable.
    • Version source: stated in documentation (emonSD_download_page.html and emoncms_README.md).
    • Runtime dependencies stated in emoncms_README.md and distribution info:
      • PHP: version 8.1.12 tested (8.1.27 installed on emonSD-01Feb24)
      • Apache: version 2.4.54 tested (2.4.57 installed on emonSD-01Feb24) with mod_rewrite enabled
      • MariaDB / MySQL: version 10.5.15 tested (10.11.3-MariaDB installed on emonSD-01Feb24)
      • Redis Server: version 6.0.16 tested (7.0.11 installed on emonSD-01Feb24)
      • Mosquitto MQTT: version 2.0.11 installed on emonSD-01Feb24
      • PHP Modules: php-curl, php-gd, php-mysql, php-redis (v6.0.3-dev), mosquitto (v0.4.0)
    • Emoncms Submodules / Components (versions recorded in emonSD-01Feb24 runtime info):
      • App: v2.8.1
      • EmonHub Config: v2.1.5
      • Dashboard: v2.3.3
      • Device: v2.2.3
      • Graph: v2.2.3
      • Network Setup: v1.0.5
      • Backup: v2.3.3
      • Network: v3.1.2
      • Postprocess: v2.4.7
      • Sync: v2.1.5
      • Usefulscripts: v2.3.11
      • RFM2Pi: v1.4.2
      • Avrdude-rpi: v1.0.3
      • EmonPiLCD: v2.0.1
      • Emonhub: v2.6.5
    • Check plan: vulnerability lookup: emoncms / GitHub / 11.4.11

  • Network Exposure and Default Credentials

    • Network joining: The Raspberry Pi joins local area networks via 10/100 Ethernet (RJ45) or Wi-Fi (802.11 b/g/n). In factory/initial setup mode, it hosts a standalone Wi-Fi Access Point.
    • Active Listening Ports:
      • Port 80 / 443 (TCP): Apache web server serving the Emoncms web dashboard.
      • Port 22 (TCP): OpenSSH server. SSH access is disabled by default; enabled by creating /boot/ssh on the boot partition or by pressing the front panel button (S1) for 5 seconds.
      • Port 1883 (TCP): Eclipse Mosquitto MQTT broker.
      • Port 6379 (TCP): Redis server (bound to localhost 127.0.0.1).
      • Port 3306 (TCP): MariaDB / MySQL database (bound to localhost 127.0.0.1).
    • Documented Default Credentials (explicitly cited in emonSD_download_page.html):
      • Local Emoncms: username emonsd, password emonsd
      • SSH: username pi, password emonsd (default — user prompted to change)
      • Wi-Fi Access Point: SSID emonpi, WPA2 Password emonpi2016 (or SSID emonsd / Password emonsd2022 on 2022 images)
      • MQTT Broker: username emonpi, password emonpimqtt2016
      • MySQL Database: username emoncms, password emonpiemoncmsmysql2016

External URLs and Downloads

  • Hardware schematic and board design files: https://github.com/openenergymonitor/emonpi/tree/master/hardware
  • OS image downloads (UK mirror): https://openenergymonitor.org/files/emonSD-01Feb24.zip
  • System provisioning scripts: https://github.com/openenergymonitor/EmonScripts
  • Emoncms repository: https://github.com/emoncms/emoncms
  • Documentation portal: https://docs.openenergymonitor.org/

PCB Fabrication Specifications

  • Layer count: 2-layer PCB (Layer 1 Top, Layer 16 Bottom)
  • Outline dimensions: 99.10 mm width × 76.00 mm height (rectangular outline with standard Raspberry Pi HAT corner radius and connector cutouts)
  • Board thickness: 1.6 mm nominal
  • Copper weight: 1 oz (35 µm) outer layers
  • Minimum trace width / clearance: Approx 8 mil (0.2 mm) trace / 8 mil clearance
  • Solder mask: White silkscreen over red or blue solder mask (standard OpenEnergyMonitor style)
  • Surface finish: Lead-free HASL or ENIG (recommended for 0603 passives, TQFP-32, and castellated RFM69CW pads)
  • Fiducials: 4 optical fiducials (1.0 mm exposed copper with solder mask pull-back) located near board corners for automated SMT assembly.