(under construction)

Project duration: ~6 months
Period: 2017
Activities: Idea, proof of concept, design electronics and firmware, prototyping, production, support & warranty
Technologies: STM32 Cortex M4, GPRS, C, USB,FreeRTOS, FatFs, LwIP (TCP/IP, NetConn, PPP), HTML, JSON, AJAX, GPS, micro-SD, Maxbotix, Arduino shield, DipTrace, EmBits

Description:

Development of a measurement and recording device for tidal water level for hydraulic survey applications.

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Specifications:

  • Ultrasonic water level meter, range 30-500cm with 1mm resolution
  • Temperature and barometric pressure sensing
  • Accelleration sensor for angle compensation and motion/shock detection
  • GPS for time synchronisation, position report and geofencing
  • Various analog and serial data inputs for third party sensors
  • Bi-stable relay output for water-level based switching (eg pump control)
  • Networking via 3G/GPRS, Xbee or LoRa
  • Supports HTTP, Telnet, FTP, MQTT, raw TCP and custom telemetry
  • Data reporting triggered by various events; geofence, G-force (shock), inputs, periodic, etc
  • Redundant data-logging to non-volatile memory and onto micro-SD card
  • Operating voltage 8-32VDC with maximum power point tracking
  • Battery option 1; 3pcs D-cell 1.5V alkaline or 3V lithium batteries
  • Battery option 2; 6V 2.5Ah lead acid
  • Arduino compatible shield headers for internal expansion possibilities
  • Optional DC/DC converter for power to third party sensors
  • IP67 Enclosure 12x12x8cm with pole mount
  • Various M16x1.5 cutouts for IP68 connectors & cable glands

Sensors:

An ultrasonic distance measurement sensor provides the primary function of water level measurements. This sensor is supplemented by an inclination sensor to compensate for angled installation and by ambient data for speed of sound correction. These additional sensor values can also be sent and logged as independent data.

Networking/telemetry:

Various radio systems can be used with the system. When real-time data is not required, then the system can also be configured for logging only, with the added benefit of less power consumption.

LoRa radios in combination with high-gain yagi antennas can provide a line of sight connection over a distance up to 100km.

Power supply:

The system can run off internal batteries or from an external power source in the range of 5V to 32V (8Vmin for charging). The internal battery is either a lead-acid based battery with about 15Wh capacity and rechargeable via the DC power input. Or a triple D-cell primary battery, which supplies up to about 70Wh with standard alkaline batteries or up to about 160Wh with 3V lithium batteries. All of these battery types allow operation with temperature ranging between -30°C and +85°C, although available energy will be affected at both extremes. Battery monitor and gauge provide estimates of consumed power and help in estimating remaining run time.

External power can come from a permanent source such as mains-powered 12V adaptor, or from a small solar panel. In applications with permanent power availability, no internal battery is required. In case of solar, the lead-acid battery is recommended. This stores enough power for substantial time without sunlight.

ARM Cortex M3

XBEE is a trademark of Digi International Inc.