Bonus bat fact: In a single midsummer night, the 15 million Mexican free-tailed bats from Bracken Cave in central Texas eat more than 140 tons of insects.That’s about the same weight as 20 elephants or one medium sized Blue Whale.
Disclaimer: the following is probably not practical but is definitely fun.
While experimenting with these bat detectors I tried to think of simple ways to display frequency; one of the main ways of identifying different kinds of bats. Since an oscilloscope is essentially a dot that scans across a screen at specific rates to display frequency and voltage, why not spin a bat detector to simulate the moving dot?
In that spirit I designed an elongated board using the same schematic and blue tacked it to a USB fan.It is difficult to see in the video and photo but it is possible to see some of the components of the ultrasonic chirps.Varying the speed and setting up triggers might provide better details but that will have to wait for another day.
Feel free to make suggestions in the comments.