Amateur Weather Stations

Transcription

1 Amateur Weather Stations Part 2 Baro Sensor / GPS Receiver / Anemometer Kurt Kochendarfer, KE7KUS Sacramento Mountains Radio Club

2 Overview Review Barometric Pressure Sensors Temperature / Pressure / Humidity GPS Receivers Position Sensor Time Sensor Ultrasonic Anemometers

3 Review In Part 1 we investigated basic requirements to develop a personal amateur weather station Stations can be tailored to your custom needs Temperature Pressure Relative Humidity GPS Lightning Detector Anemometer Rain gauge Bus communications

4 Barometric Pressure Sensor Many different pressure sensors are available on the market Which sensor do I use? System design redundancy / data averaging considerations Backup sensors Required level of precision Voltage levels BEWARE!

5 Barometric Pressure Sensor MPL3115A2 I2C bus sensor Altitude resolution to 0.3 meters Interrupt outputs / low power consumption Built in temperature sensor (+/- 1 C) MPL3115A2 Baro Sensor $6.37

6 Barometric Pressure Sensor BME280 I2C Bus Temperature (+/-1 C) Humidity (+/-3%) Pressure (+/- 1 hpa) BME280 vs. BMP280 Can replace DS18B20 & DHT22 w/ single unit BME280 Pressure Sensor $3.28

7 Barometric Pressure Sensor BME680 Similar in function to BME280 Adds MOX gas sensor Detect VOCs...measure air quality BME680 Pressure Sensor $

8 Barometric Pressure Sensor Baro sensor can be used as an altimeter as long as SLP is known Rough approximations yield values within 10 s of meters Arduino libraries support BME280 & MPL3115A2 Baro pressure trends can predict: Air mass movement / frontal boundaries = precipitation Sharp pressure gradients = windy conditions

9 GPS Receiver NEO-6M 50-channel GPS receiver SBAS: WAAS (2.0m precision) ~160dBm sensitivity 1 PPS time pulse RMS accuracy: 30ns NMEA 0183 Serial Output GLONASS & others support via Arduino libraries NEO-6M GPS Receiver $7.60

10 GPS Receiver ublox NEO-7M 56-channel GPS receiver SBAS: WAAS (2.0m precision) ~160dBm sensitivity 1 PPS time pulse GPS RMS accuracy: 30ns GLONASS RMS accuracy: 50ns NMEA 0183 Serial Output GLONASS support built-in (4.0m precision) NEO-7M GPS Receiver $9.28

11 GPS Receiver Enables precision position reporting (if desired) Micro/nano climate reporting GPS altitude vs. barometrically computed altitude Enables precision time reporting (definitely desired) Timestamp weather observations Keeps up with even highest sensor sample rates Enables secondary function of Stratum 1 NTP time server

12 GPS Receiver Network Time Protocol (NTP) Utilized to automatically sync time amongst all network participants Used by virtually every computer operating system in use Stratum 1 Time Server Next most accurate timepiece to an atomic clock Time precision is only limited by GPS timepiece Can be used to provide network time for entire home network If internal Stratum 2 server used network time accuracy ~100μs

13 Ultrasonic Anemometer In Part 1 we investigated the cost of a traditional spinning cup / wind vane anemometer ($88) Not particularly desired due to mechanical moving parts Parts wear out and must be replaced High end weather stations use ultrasonic transducers to measure wind direction/speed Gill Windobserver Anemometer $

14 Ultrasonic Anemometer Theory of operation Wind Velocity 20mph 40KHz Transducer Sound Velocity* ~750 mph 40KHz Transducer Distance (d) = Time (T) x Velocity (V) * Sound velocity highly dependent on temperature/humidity calculations

15 Ultrasonic Anemometer Several different sensor configurations All use variations in time-of-flight to measure wind velocity/direction Sound pulse PRF allows extreme precision wind sampling Sample rates of up to 20Hz are possible NWS current reporting standard is a 5 second average Our station gives better idea of peak gusts Allows us a higher fidelity picture of damaging wind gusts

16 Ultrasonic Anemometer JSN-SR04T Waterproof Ultrasonic Transducer 40kHz 30mA Working Current Weatherproof Remote Sensor JSN-SR04T Transducer $8.85

17 Ultrasonic Anemometer Significant programming required to turn sound waves into usable data Amateur-built Ultrasonic Anemometer Significantly less than $

18 Summary With quality BME280-type sensors, we can simplify our station or add redundancy GPS brings VERY affordable precision time standards to our station (+ our home network, if desired) With simple ultrasonic sensors we can obtain precision wind measurements (and rain?) Questions? Kurt Kochendarfer, KE7KUS Sacramento Mountains Radio Club