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Psychrometer

A family of miniature, ultra-low-power autonomous temperature, humidity and pressure sensors that report periodically to a single hub over a 2.4 GHz nRF24L01+ star network.

Version: 0.1.0 | Status: concept


Overview

Each sensor node samples a BME280 (temperature / humidity / pressure), transmits the reading to the hub, and returns to deep sleep. The MCU spends almost all of its life in low-power mode, waking once every transmit period. Battery life is measured in years; an outdoor variant runs from a small solar panel.

The hub collects readings from every node and displays them on an LCD.

graph LR
  S1[Indoor node<br/>MSP430G2553 + BME280] -->|2.4 GHz| HUB
  S2[Indoor node<br/>MSP430G2553 + BME280] -->|2.4 GHz| HUB
  SO[Outdoor node<br/>+ solar] -->|2.4 GHz| HUB
  HUB[Hub<br/>STM32F103C8T6 + LCD] --> LCD[(Display)]
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Hardware

Role Part Notes
Node MCU TI MSP430G2553 16 KB Flash, 512 B RAM, ~0.1 uA LPM3/4
Sensor Bosch BME280 T / H / pressure, ~0.1 uA sleep, I2C
Radio nRF24L01+ (GT-24-Mini) 2.4 GHz, SPI, 3.3 V supply and logic
Node power CR2032 / 2xAA Li battery
Outdoor power 5.28 V / 0.37 W solar + LiFePO4/supercap self-sustaining
Hub MCU STM32F103C8T6 64 KB Flash, 20 KB RAM, + LCD
Hub radio nRF24L01+ same RF, PRX role

Network

  • Topology: star - up to 20 nodes, ~10 planned plus expansion.
  • Range: single apartment / small house.
  • Transmit period: 10 minutes default (indoor and outdoor).
  • Reliability: nRF24L01+ auto-ACK with retransmit; each node has a unique pipe address.

Repository layout

Path Purpose
inc/ Public headers
src/ Common application sources
docs/ Doxygen config and diagrams
requirements.md Requirements and task backlog
HISTORY.md Milestone log
CHANGELOG.md Versioned change log

License

See LICENSE.

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A family of miniature, ultra-low-power autonomous temperature, humidity and pressure sensors.

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