This is a wireless sensor network system as a part of an ongoing project for smart home sensing and security. The intent is to create easily deployable, low-maintenance (thereby low-power) sensors for real-time collection of non-sensitive data. The various sensors have a battery life typically between 1-4 years off a CR2032 (excl. CO2SN - 4 months, Li-ion).
The data is collected in InfluxDB and can be viewed graphically in Grafana.
These devices either contribute to the WMNS database or utilize it for their functions.
PMS - Particulate matter sensor.
IN-16 Display - IN-16 tubes for displaying database information.
E-Paper Display - Simple Wi-Fi/BLE enabled e-paper display. Designed for displaying real-time sensor data.
Lamp - Mood lamp simulating candle flicker.
Transposer - Python script to transfer data from InfluxDB to Firebase RTDB.
This wireless mesh network is a proprietary, decentralized flood type network. The network consists of three distinct node types: routers (R), gateways (GT) and low-power end devices (LP).
Routers retransmit received data to form the backbone of the network.
Gateways are similar to routers and forward mesh network data to a server/cloud.
End devices are low-power nodes that sleep for most of the time, periodically transmitting data.
Currently, the following data is collected by the system through multiple sensor types (sensors in brackets, not necessarily utilized as such):
- Temperature (BME280, BME680, Si7021, SCD41, BMA400, mcu_internal)
- Relative humidity (BME280, BME680, Si7021, SCD41)
- Barometric pressure (BME280, BME680)
- Illuminance (OPT3001, VEML6030, Si1133/5)
- UV levels (Si1133/5)
- Sudden/discontinous motion (BMA400)
- Person counter (VL53L1X)
- CO2 concentration (SCD41)
- VOC concentration (BME680)
- Battery levels (ADC)
- Signal strength (radio)
| GPSN | LRSN | CO2SN | ALSN |
|---|---|---|---|
 General-purpose configurable sensor for: temperature, humidity, air pressure, light, VOCs, motion |
 Person counter sensor |
 Carbon dioxide concentration sensor |
 Specialized light sensor for visible, UV, IR |
| GATEWAY | ROUTER32PA | ROUTER40 | LTSN | TERMINAL |
|---|---|---|---|---|
 Internet gateway node |
 Power amplified router node |
 USB-powered router node |
 Specialized temp sensor for sub-zero |
 Security node and gateway redundancy. |
The following performance factors were considered during the design of the WMNS:
- Low maintenance - essentially long battery life and reliability
Low power circuit and software design from bottom up. Certain sensors (i.e those expected to face harsher conditions) are conformally coated to increase reliability.
Network has no central "coordinator" type node which is required to sustain the network. Packets can take multiple paths to the gateway. Gateways can be configured as redundancies.
Connectionless protocol. No risk of runtime disconnections, failed acks etc. Sensors only need initial positioning in an area with good RSSI and reasonable packet loss from multipath fading. - Ease of use - able to easily add more sensors (and more types), and modify configurations.
Easy plug-and-play to add more sensors. Only the gateway needs modifications to add new sensor types (for database side processing).
Sensors can easily be configured for different sample rates. - Range - good wireless range vs power consumption compromise
Tuned internal antennas allow for lower tx power (and less power consumption).
- Low-cost - cheap sensors
Runs off comparatively low-cost and widely used nRF52 series SoCs. Same design template was used across sensors to drop development time and costs.
No protocol overhead or IP costs involved.
This system has been deployed in stages since Q1 21 with zero system failures (e.g gateway restarts, sensor malfunctions and drops out of network, hardware failure).
Deployed devices: 28
This repo is released under the GPL-2.0 License. Related repos DO NOT INHERIT licenses.