User:Bertrik Sikken

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User info Bertrik Sikken
Name Bertrik Sikken
Nick bertrik
Tagline heb ik niet

You can reach me at or

Studied Electrical Engineering at Twente University.

Main interests:

  • reverse-engineering things (USB stuff, mp3 players), working on
  • studying bats and making electronics for recording/listening to bat sounds
  • radio stuff, in particular software-defined radio

Projects I work(ed) on (refresh):

 Project Status
DecodingLoraIn progress
EncodingLoraIn progress
EspWifiTrackerIn progress
LoraWanNodeIn progress
RevRadioIn progress

Project ideas

This is a list of ideas I'm thinking about, but have not fully developed into an actual project yet.

LoRa HAB receiver

This is a receiver for high-altitude balloons sending telemetry using LoRa modulation in the 70 cm radio band.

Status: ordered the Pi LoRa board, verified that the receiver software can be compiled (on a PC).

Basically we need the following:

Here's a guide for building a HAB LoRa "gateway".

Inexpensive CO2 sensor

Status: works as a basic MQTT sensor, see topic "bertrik/co2" on

Use the MH-Z19 sensor module (about E22,-) to measure the CO2 concentration and an ESP8266 (like a WeMos D1 mini board) to push the measurement data over the internet to a MQTT server. Possibly I can use ESPEasy which makes configuration easy (through a web interface), I'd have to add support for this particular sensor -> ESPEasy seems pretty complicated to get changes accepted, has existing bugs that are not addressed, probably better to write my own custom code.

Further Understanding LoRa

Ultimate goal is to create an SDR algorithm to decode LoRa without the need for dedicated LoRa hardware. This could be useful when tracking HABs transmitting LoRa for example. See DecodingLora.

Cypress PSOC5

Play with the Cypress PSOC5 platform, which combines a ARM Cortex-m3 processor with configurable analog blocks. I'm thinking of combining it with a 24 GHz doppler radar sensor, to process the signal and present it as a USB audio device (stereo signal contains I and Q parts). See RadarOnAStick.

Android HabAlert app

see HabAlertApp

Inexpensive ultrasonic player

Bat netting results can be improved by playing back ultrasonic bat calls near the net. This project idea is about creating an inexpensive ultrasonic player by cleverly combining inexpensive sub-modules available already on the market.

The ultrasonic player consists basically of the following parts:

  1. a device to store the bat calls (in wav-format) and playing them back in a particular sequence from storage, like a laptop, tablet or raspberry pi
  2. a device to convert the digital audio into an analog audio signal, like a USB "sound card"
  3. a device to amplify the analog audio signal
  4. a device to reproduce the analog audio signal into actual ultrasonic audio, i.e. a speaker
  5. a case to put everything together
  6. a power supply

Ultrasonic audio from bats can range to well over 100 kHz. Sampling theory says that to reproduce a bandwidth of B Hz, you need a sampling rate of at least 2*B.

An USB sound card supporting 96 kHz playback would allow ultrasonic audio up to 48 kHz to be reproduced, possibly enough for use in a bat lure. A possible inexpensive candidate is this ES9023 based USB sound card, costs about E22.-

To amplify the audio signal, I'm thinking of this TDA2030 based amplifier board, costs about E1,- The TDA2030 is an analog amplifier block. It takes (a minimum) of 12V and can output up to 14W. The datasheet claims it has a power bandwidth of 10 Hz to 140 kHz.

As a speaker, I'm thinking of this tweeter Vifa/Tymphany XT25SC90-04, costs about E22,-

As a case, I could create a simple box using our laser cutter, with some tie wraps to hold the parts inside the box.

Power supply:

  • the USB audio card uses USB 5V.
  • the amplifier needs 12V

Perhaps we can use a switching power supply to create the 12V from the USB 5V? It would be nice if everything could be fed off the USB 5V. Possible candidate: 5V-to-12V step-up cable, costs about E3,-

Another USB 5V to 12V converter, switching at 1MHz.