Bill of materials
Description
The production BOM is for a repeatable kit that Gratheon can sell, support, calibrate, and service. It should be based on field MVP evidence, not guessed upfront. The goal is supply-chain resilience, waterproof serviceability, consistent scale mechanics, and device health telemetry.
Functionality covered
- Calibrated load-cell frame or repeatable calibration workflow.
- Secure device identity and web-app pairing.
- Battery, solar, and device-health telemetry.
- Waterproof connectors and strain relief for maintenance.
- Optional gateway connectivity for apiaries without WiFi.
- Optional research sensor variants after the base scale is reliable.
Bill of materials
| Tier | Component | Example part | Qty | Rough cost | Purchase links | Notes |
|---|---|---|---|---|---|---|
| Required | MCU module or carrier | ESP32-WROOM module, ESP32-C3 module, or pre-certified dev module | 1 | €3-12 | ESP32 module at DigiKey, ESP32 modules at Mouser, Existing ESP32 notes | Use pre-certified modules to reduce compliance risk. |
| Required | Custom PCB or carrier board | ESP32 carrier with HX711, power, connectors, and debug header | 1 | €5-25 | JLCPCB, PCBWay, LCSC components | Production should remove fragile jumper wiring. |
| Required | Scale frame | Aluminium or stainless calibrated hive-scale frame | 1 | €40-120 | Existing aluminium profile, local metal workshop, Alibaba platform-scale examples | Mechanical repeatability matters more than cheapest electronics. |
| Required | Load cell | 100-200 kg single-point or industrial platform-scale cell | 1 | €15-60 | Amazon 200 kg load-cell search, AliExpress 200 kg single-point load-cell search, Alibaba supplier examples | Select after testing frame geometry. |
| Required | Weight ADC | HX711 or production-grade 24-bit ADC | 1 | €1-10 | SparkFun HX711 breakout, Adafruit HX711 breakout, LCSC HX711 sourcing | HX711 is acceptable if field drift/noise is acceptable. |
| Required | Temperature probe | Waterproof DS18B20 with service connector | 1 | €3-12 | Adafruit waterproof DS18B20, Existing DS18B20 notes, industrial M8/M12 probe suppliers | Add connector and strain relief for replacement. |
| Required | Humidity/ambient sensor | SHT31/BME280 in vented protected housing or replaceable pod | 1 | €5-20 | Adafruit SHT31-D breakout, Adafruit BME280 breakout, distributor SHT31 modules | Use enclosure design that prevents condensation pooling. |
| Required | Power system | Protected battery pack, charger, fuse/protection, power switch | 1 | €15-45 | Adafruit solar LiPo charger, Adafruit PowerBoost 1000, local battery-pack supplier | Production must document safe charging and replacement. |
| Required | Battery telemetry | MAX17048/LC709203 fuel gauge and optional solar voltage sensing | 1 | €3-12 | Adafruit MAX17048 fuel gauge, Adafruit LC709203F fuel gauge, Adafruit INA219 | Enables support workflows and proactive alerts. |
| Required | Enclosure | UV-resistant IP65/IP67 enclosure | 1 | €10-35 | Hammond enclosure search at Mouser, Amazon IP67 enclosure search, local electrical supplier | Prefer consistent branded enclosures for production. |
| Required | Waterproof connectors | M8/M12, sealed circular connectors, or rated cable glands | as needed | €8-35 | M8 connector search at Mouser, Amazon M8 waterproof connector search, local electrical supplier | Makes probes, load cells, and solar panels replaceable. |
| Required | Strain relief and cable labels | Internal cable clamps, glands, ferrules, labels | 1 set | €3-12 | Local electrical supplier, Amazon ferrule kit search | Prevents cable pull from reaching PCB or solder joints. |
| Recommended | Solar panel | 5-6 V or 12 V panel sized from field energy data | 1 | €10-40 | Adafruit 6 V solar panel, Amazon 6 V solar panel search, local solar supplier | Size after measuring sleep current and radio duty cycle. |
| Recommended | Gateway option | ESP32 LoRa, Raspberry Pi, or cellular gateway | 1 per apiary | €20-120 | LilyGO LoRa32 examples, Raspberry Pi, Adafruit FONA/SIM module category | Prefer one gateway per apiary over cellular in every hive. |
| Recommended | Factory test fixture | Known weights, frame jig, pogo-pin flasher, seal inspection checklist | 1 set | varies | Local workshop, electronics lab suppliers | Required for repeatable production QA. |
| Optional | Tamper/vibration | IMU, tilt switch, or vibration module | 1 | €2-15 | Adafruit LIS3DH accelerometer, Existing tamper/vibration note, AliExpress vibration sensor search | Add only after weight and battery alerts are stable. |
| Optional research | Acoustic module | MEMS microphone or analog microphone module | 1 | €3-15 | Adafruit I2S MEMS microphone, Existing microphone note, SparkFun microphone boards | Requires placement and ML validation before product promise. |
| Optional research | CO2/VOC/air-quality | ENS160, SCD40/SCD41, or other environmental module | 1 | €10-60 | Adafruit SCD-40 CO2 sensor, Existing air-quality notes, Existing ENS160 todo | High power and condensation risk, keep as research variant. |
Connectorized subsystem BOM
| Subassembly | Included parts | Buy/build note |
|---|---|---|
| Load-cell harness | Shielded 4-wire or 6-wire cable, M12 connector or sealed gland, internal terminal | Keep analog cable short. Add shield/drain only if grounding plan is defined. |
| Temperature probe harness | Waterproof DS18B20, 3-pin connector, strain relief | Standardize pinout: 1 = 3.3 V, 2 = data, 3 = GND. |
| Ambient pod | SHT31/BME280 board, vented cap, short I2C cable, gasket | Treat as replaceable consumable if field drift appears. |
| Power harness | Battery connector, fuse/protection, switch, solar connector | Use keyed connectors to prevent reversed polarity. |
| Service harness | Internal UART/JTAG header or pogo pads | Avoid external USB openings on production enclosure. |
| Gateway kit | LoRa/ESP-NOW node firmware, apiary gateway enclosure, gateway power | Keep gateway as a separate SKU or add-on. |
Supplier examples to compare
These are prototype/vendor research links, not final approved suppliers:
- Alibaba industrial load-cell scale example
- Alibaba stainless waterproof scale example
- Pilot Scale bench-scale series
- Alibaba RS485 weighing scale example
- Alibaba X-type stainless scale example
Selection rules before ordering production parts
- Each critical part needs at least two acceptable suppliers or an approved substitute.
- Connector pinouts must be documented before harnesses are ordered.
- Enclosure, connector, and cable diameter must be checked together, not separately.
- The load-cell capacity must include hive weight, honey peak, beekeeper handling, and overload margin.
- The battery chemistry and charger must be documented for safe shipping and service.
- The frame and electronics revision must be recorded in telemetry metadata.
Exit criteria
- Two or more identical units produce comparable weight trends after calibration.
- Device can be paired to a Gratheon hive without manual database edits.
- Support can see battery, RSSI, firmware version, last seen, and reset reason.
- Enclosure and connectors can survive realistic rain, UV, and service handling.
- Supply chain has at least two acceptable sources for each critical component.