Living at the edge of a field, there is often damage caused by martens, often also to the car. I have already tried a few things and can say with certainty that classic tips such as toilet stones, dog hair, wire mesh, etc. are of no use. There are a lot of 'marten/rodent protection' devices available for sale, especially for cars, but often the technical specifications are inconclusive or the devices are ineffective. One of them has even ruined the battery of our camper by deep-discharge after failure.

From experience I can say that the combination of high voltage and ultrasonic seems to work well: The animal gets a (harmless!) electric shock and learns from it to avoid places with this characteristic signal in the future. According to common opinion, about 0.1 - 0.25 joules are sufficient for the strength of the electric shock, and martens can hear up to >30kHz. Therefore, the ultrasonic signal is in the range between 18kHz and 26kHz and consists of 3 short tones. The signal is repeated every few seconds and is unpleasantly (but not yet harmful to health) loud (approx. 100 dB), but hardly perceptible to humans. Important: Even inaudible, extremely loud, continuous noises can cause hearing damage - in humans and animals. This was taken into account during development.

Special emphasis was placed on low power consumption for the 'Marderli', so that the device can be operated for months on batteries without any problems and still provide full performance. And, of course, on the operability via BLE: Thus, the technical data (e.g. voltage, triggers, quality of the high-voltage insulation, ...) can be queried or changed (e.g. BLE name or the setup) very easily at any time.

  • Designed for use with 9 - 14 volts (either from batteries or vehicle electrical system. Important: older vehicles sometimes have voltage peaks >14 volts, see HW documentation).
  • Power consumption consists of subcomponents:
  • BLE 'only', unconnected: <20uA
  • BLE 'only', connected with APP: <50uA
  • High-voltage generation with good insulation: approx. 32uA
  • High-voltage generation with poor insulation: up to 500uA
  • In case of short-circuit at the high-voltage output: (depending on the HW structure): approx. 0.1 - 10 mA
  • Generation of the periodic ultrasonic signal (depending on volume, see HW documentation): approx. 0.1 - 1.2 mA
In normal operation (and at moderate volume), the device remains well below 0.5mA, i.e. with standard batteries of the size '18650' and 3500mAh you can bridge more than 6 months without problems and without using the car battery! At voltages <9V, the unit switches off high voltage and ultrasonic!

  • Segger Embedded Studio (SES) Version 6.22a
  • Nordic SDK 17.1.0
  • (Almost any kind of) Module with NRF52832 (SoC from Nordic)
  • Complete sourcecode from https://github.com/joembedded/open_sensor_blue_public
  • Complete High-Voltage Simulation with LTSpice (free) in the Github-Repo