Although the EE2016 ultrasonic bat detector as published on this website works quite well (using the kit's 40kHz transducers), I felt there was potential to improve on both sensitivity, frequency range and functionality. Since I am fond of using the SA612A (NE602A) mixer chip (see the superhet radio), I stumbled upon Bertrik Sikken's analog design for a bat detector and extended it with a broad-range MEMS-microphone (20 - 120kHz), a different audio circuit (based on the TDA7052A) and a microcontroller (PICAXE-08M2) to allow for a LCD/OLED display and an automatic frequency sweeping mode. The initial setup is shown here, which reveals that another goal was to see how designing my own front panel for the EE1000 works out in practice:


The resulting device is actually performing very well, also through the help of many contributors (see links below) and I can really recommend building it (but then please check these links). Note that one can easily exchange the audio circuit and the microcontroller type with another one that suits better.

Here follows more information on the latest versions of the design and the discussion links:

Electrical Circuit Diagram and required microcontroller software to have it operational:


The bat detector in action:


Finally, after being fully satisfied with the electrical design, I took the soldering iron and developed a version for practical use in a nice wooden box and ditto layout:


The design (electrical, as well as the final box version) benefitted greatly from the contributions of others: