OWB Monitor - Bill of Materials
Parts list for the outdoor wood boiler monitoring node. Monitors supply/return temperatures on two hydronic loops and pump current draw on each circulator pump.
Sensors
| Part | Qty | Interface | Purpose | Est. Cost (CAD) |
|---|---|---|---|---|
| DS18B20 waterproof probe (2m lead) | 4 | 1-Wire | Supply and return temp on house loop and barn loop | ~$14 |
| SCT-013-030 CT clamp (30A, voltage output) | 2 | Analog (0-1V) via ADS1115 | Current draw on each circulator pump | ~$17 |
| ADS1115 16-bit ADC breakout | 1 | I2C (addr 0x48) | Converts CT clamp analog signal to digital for ESP32 | ~$6 |
DS18B20 Notes
- Use the waterproof probe version with a stainless steel tip, not the bare TO-92 package
- Pipe-clamp mounting: thermal paste between probe and pipe, secured with a hose clamp
- All four sensors run on a single 1-Wire data bus (one GPIO pin)
- Each sensor has a unique address burned into the chip - run a 1-Wire scan to discover addresses before configuring
SCT-013-030 Notes
- The SCT-013-030 is the voltage output version with a built-in burden resistor
- Output: 0-1V AC proportional to 0-30A measured current
- Clamps around a single conductor only - clamping around both wires in a cable produces a null reading (currents cancel)
- No external signal conditioning needed - connect directly to ADS1115 input
ADS1115 Notes
- 16-bit ADC, 4 channels, I2C interface
- Default address 0x48 (addr pin to GND)
- Two differential channels used: A0_A1 for house pump, A2_A3 for barn pump
- Gain setting: 0.256V in config.json (tightest usable range for 0-1V CT clamp signal, best resolution)
- Calibration: multiply factor in firmware config – fine-tune against a clamp meter reading on-site
Controller
| Part | Qty | Purpose | Est. Cost (CAD) |
|---|---|---|---|
| LILYGO T-SIM7080-S3 | 1 | Main controller (ESP32-S3 + Cat-M1 cellular) | ~$46 |
Pin Assignments
Confirmed against the LILYGO T-SIM7080-S3 board:
| Function | GPIO | Notes |
|---|---|---|
| 1-Wire (DS18B20) | GPIO12 | Single data bus for all four temp sensors |
| I2C SDA (ADS1115) | GPIO1 | |
| I2C SCL (ADS1115) | GPIO2 |
Monitored Outlet Box (Planned)
A custom plug-in enclosure that the circulator pumps plug into. Each outlet is wired through a CT clamp for current monitoring. No panel work or hardwiring required.
| Part | Qty | Purpose | Est. Cost (CAD) |
|---|---|---|---|
| 2-outlet box (120V, standard) | 1 | Enclosure for monitored outlets | ~$10 |
| 14 AWG cable + plug | 1 | Input cable with standard plug | ~$8 |
The pumps plug into the box. The box plugs into a standard wall outlet. Each CT clamp goes around the hot conductor inside the box for each outlet.
Mounting and Consumables
| Part | Qty | Purpose | Est. Cost (CAD) |
|---|---|---|---|
| Hose clamps, 1” range (e.g. 3/4” - 1-1/4” adjustable) | 4 | Secure DS18B20 probes to ~1” OD pipes | ~$4 |
| Thermal paste | 1 tube | Thermal contact between probe and pipe | ~$5 |
| USB-C cable + 5V/2A power supply | 1 | Power for the LILYGO board | ~$12 |
| Temporary enclosure | 1 | Protects the board during initial deployment | ~$8 |
Enclosure Notes
The initial deployment uses a temporary enclosure. Permanent housing will be 3D-printed in ASA (heat and UV resistant). That is a separate future step.
Total Estimated Cost
| Category | Est. Cost (CAD) |
|---|---|
| Sensors (DS18B20, CT clamps, ADC) | ~$37 |
| Controller (LILYGO T-SIM7080-S3) | ~$46 |
| Monitored outlet box | ~$18 |
| Mounting and consumables | ~$29 |
| Total | ~$130 |
Sourcing
Almost everything comes from AliExpress. Lead times to Canada are typically 2-4 weeks, so order early. The cost savings are significant - most components are 30-60% cheaper than domestic alternatives.
Amazon or Digi-Key are fallbacks for when you need something fast (2-3 day shipping) and are willing to pay the premium for it.
| Source | When to use | Parts |
|---|---|---|
| AliExpress | Default for everything | DS18B20 probes, SCT-013-030 clamps, ADS1115, LILYGO board, USB-C supply, hose clamps, enclosures |
| Amazon | Need it this week | Thermal paste, USB cables, hose clamps if sizing is wrong |
| Local hardware store | Same day | Outlet box, 14 AWG cable, wire nuts |
| Digi-Key | Specific part not on AliExpress, or need exact specs fast | ADS1115 breakout (verified datasheet), precision resistors |
The BOM prices above are based on AliExpress pricing. Sourcing the same parts from Amazon or Digi-Key would roughly double the total cost.