Published February 29, 2016 © CC BY-NC-ND

Wireless Temperature and Humidity Sensor with Encryption

Arduino based wireless temperature and humidity sensor, can run for 1 year on single 14505 battery, and data transmission is encrypted.

IntermediateWork in progress1 hour3,872

Wireless Temperature and Humidity Sensor with Encryption

Things used in this project

Hardware components

Moteino

moteino

HopeRF TH02 Humidity Module

Single AA battery holder

3.6V 2.4Ah Li-SOCl2 battery

Custom Moteino Shield from OSH Park

Software apps and online services

Arduino IDE

Hand tools and fabrication machines

Soldering iron (generic)

Story

Monitor the temperature and humidity with a small wireless, battery powered Arduino based sensor. Data is transmitted every 60 seconds to a central hub, utilizing AES-128 encryption. Using a Moteino R4 with onboard RFM69W transceiver transmitting at 434Mhz, along with a custom shield with a HopeRF TH02 temperature and humidity sensor, and powered with a 3.6v 14505 Li-SOCl2 battery.

1 / 3 • Parts for project

Parts List:

Moteino R4 with RFM69W 434Mhz radio
HopeRF TH02 Temperature and Humidity Sensor
Custom Moteino Shield from OSH Park
Single AA battery holder
14505 3.6V 2.4Ah Li-SOCl2 battery

Basic Idea:

Every 60 seconds the Moteino wakes up, takes temperature, humidity, dewpoint, and transmit data to a central hub. The battery voltage level is also transmitted.
The TH02 is powered from a digital pin, digitalWrite() is used to turn on/off (for power savings).
radio.sleep() is used to power down the RFM69W radio after transmission.
LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF) is used to sleep the Moteino between transmissions.
The max draw during transmission is very close to the pulse capability of the battery (~250 mA).
Utilizing the built-in AES-128 encryption provided by RFM69W radio.
Data is written to a SQLite3 database, with processing being handled by NodeJS.

Code

Untitled file

  //  sample of how I'm shutting down the MCU for power-savings
  //
  void setup() {
  //
    //  power on TH02
    pinMode(si7005Vcc, OUTPUT);
    digitalWrite(si7005Vcc, HIGH);
    //
    //  disable heater and enable fast measurement (less time spent sampling)
    Si.disableHeater();
    Si.enableFastMeasurements();
  }
  //
  void loop() {
  //  Turn serial back on
    Serial.begin(SERIAL_BAUD);
    //
    //  turn TH02 back on
    digitalWrite(si7005Vcc, HIGH);
    //
    .....
    //
    //  shutdown devices and idle for ~60 seconds
    Serial.flush();
    Serial.end();
    radio.sleep();
    digitalWrite(si7005Vcc, LOW);
    //
    for (int count = 0; count < 7; count++) {
      LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
    }
  }