Bill of materials

Description

The field MVP BOM is the first outdoor kit. It should be weatherproof, battery-powered, and useful for pilot beekeepers, but still built from common modules rather than a custom PCB.

Functionality covered

  • Measures hive weight with one 100-200 kg load cell or four 50 kg bar cells.
  • Measures internal temperature with a waterproof DS18B20 probe.
  • Measures ambient temperature and humidity in a vented protected location.
  • Measures battery voltage or charge state for low-battery warnings.
  • Reports every 10-15 minutes and batches data when WiFi is unavailable.
  • Uses a weatherproof enclosure, cable glands, and field-safe wiring.

Bill of materials

Tier Component Example part Qty Rough cost Purchase links Notes
Required Microcontroller ESP32 DevKit / ESP32-WROOM-32 board 1 €4-10 Existing AliExpress ESP32, Espressif ESP32-DevKitC at DigiKey, ESP32-DevKitC at Mouser Same board as lab keeps support simple.
Required Weight ADC HX711 breakout 1-4 €1-16 SparkFun HX711 breakout, Adafruit HX711 breakout, Existing HX711/bar-cell notes Use one HX711 per independent load-cell channel.
Required Load cell option A 100-200 kg single-point load cell 1 €12-35 Alibaba industrial load-cell examples, Amazon single-point load-cell search, AliExpress load-cell search Best for simpler mechanics if the frame transfers load correctly.
Required Load cell option B 50 kg bar load cells 4 €8-25 total Existing 50 kg bar load cells, Amazon HX711 4-load-cell kit search, AliExpress 50 kg load-cell search Easier to source, harder to make mechanically repeatable.
Required Internal temperature Waterproof DS18B20 probe 1 €2-10 Existing AliExpress DS18B20, Adafruit waterproof DS18B20, Amazon DS18B20 search Place near brood-area edge or under cover without disturbing colony.
Required Ambient humidity/temperature SHT31, SHTC3, or BME280 module 1 €3-15 Adafruit SHT31-D breakout, SparkFun Qwiic SHTC3, Adafruit BME280 breakout Prefer SHT31/SHTC3 over DHT-style sensors for field reliability.
Required Weather enclosure IP65 electrical junction box 1 €6-18 Amazon IP65 junction-box search, AliExpress waterproof junction-box search, local electrical supplier Cheaper and easier than custom aluminium for MVP.
Required Cable glands PG7/PG9 waterproof cable glands 3-6 €3-10 Amazon cable-gland search, AliExpress cable-gland search, local electrical supplier Required for probe, load-cell, solar, and battery cables.
Required Battery power Protected 18650 cells plus holder or USB power bank 1 set €8-25 Existing 18650 battery notes, Existing 18650 shield, Amazon 18650 holder search Use protected cells and conservative charging design.
Recommended Battery telemetry MAX17048, INA219, LC709203, or resistor divider 1 €1-10 Adafruit MAX17048 fuel gauge, Adafruit LC709203F fuel gauge, Adafruit INA219 current sensor Needed for low-battery alerts and field support.
Recommended Solar charging 5-6 V solar panel plus Li-ion charger module 1 €8-25 Adafruit USB/DC/Solar LiPo charger, Amazon 6 V solar panel search, AliExpress CN3065 solar charger search Use only after battery-only baseline is measured.
Recommended Mechanical frame Aluminium profile or stainless mounting parts as needed €20-80 Existing aluminium profile, Existing screws, local hardware store MVP can use commodity profile before production frame design.
Recommended Wire ferrules / Wago / screw-terminal blocks Small field-wiring kit 1 set €3-12 Local electrical supplier, Amazon wiring-terminal search Makes cable replacement cleaner than soldered wire bundles.
Optional Bench/service display LCD1602 I2C display 1 €2-6 Existing LCD1602 notes Use only for service/debug builds, not default field kit.

Connector and cable plan

Cable Minimum MVP approach Better MVP approach Production upgrade path
Load cell Cable gland directly into enclosure Gland plus internal screw-terminal strain relief Shielded cable to M12 or rated circular connector.
DS18B20 Probe cable through PG7 gland 3-pin waterproof inline connector M8 3-pin sensor connector.
Solar panel Dedicated gland 2-pin waterproof inline connector Locking keyed connector with polarity marking.
Ambient sensor Inside vented enclosure pocket Remote small sensor pod Replaceable pod with gasket and hydrophobic vent.

Installation consumables

  • UV-resistant zip ties or stainless cable clips.
  • Butyl tape or silicone gasket sheet only where the enclosure vendor allows it.
  • Rubber feet or anti-slip pads between frame and hive stand.
  • Stainless screws/bolts for wet outdoor use.
  • Labels for device ID, hive ID, firmware version, and calibration date.

Exit criteria

  • Device survives rain-protected outdoor operation without water ingress.
  • Weight trend is useful enough to detect daily gain/loss and sudden movement.
  • Battery telemetry is visible or at least logged locally.
  • The device can run for a realistic pilot interval with the selected report cadence.
  • A beekeeper can install it without soldering inside the hive body.