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This is a design for a simple capacitive water-level sensor. As the capacitive load on the oscillator increases, it oscillates more slowly. The frequency of oscillation is captured by a pulse counter on pin 1 with a 10ms window and this is then converted to a water level.



  • This is an old design, and uses an expensive low Iq boost converter. This works well, but burns 12μA of current at all times. We will be updating this design to use the Nora-style boost that is controlled by the imp, allowing a cheaper part to be used.
  • The battery voltage is fed directly into the imp, allowing the battery level to be monitored.
  • A thermistor is also provided, allowing the temperature to be read.
  • In production, these would likely need to be calibrated, as the inverter and capacitance can vary. This calibration value would be sent back to the server and stored. However, this is not yet implemented and hence does not appear in the code.

Device Firmware and Example Code

Revision-controlled firmware to test and use the Flora board is available on the Electric Imp GitHub examples page.

Hardware Design Files