September 13, 2017 by Robin Mitchell
Track bats by making a circuit that can detect the clicks they emit.
Bats come out at night and can be difficult to spot—but with this bat detector, you will be able to track them down!
While some bats do make audible clicks, most produce inaudible clicks that are between 20kHz and 200kHz. Since vision is severely restricted at night and in caves, bats rely on echolocation, which works in a nearly identical fashion to submarine SONAR.
Essentially, the bat generates a high-frequency click that bounces off surrounding objects. The reflected click is detected by the bat and this is enough information for the bat to determine the size and type of object nearby, as well as the distance from it.
Luckily for us, these sound waves diffract and spread in mostly all directions—so if we can create a circuit that can detect these clicks then we should be able to track bats!
View the full-size schematic.
The next step is to convert the high-frequency pulse to a lower-frequency pulse for further processing. While this circuit uses an indicator LED to show that ultrasonic pulses have been detected, the circuit could easily be connected to a pair of headphones. However, the ultrasonic frequencies would be inaudible—so to make them audible, a frequency divider (4040) is used (using a division of 16 makes 200kHz signals sound like 12kHz signals).
The last step is to turn on an LED but this LED cannot directly connect to the output of the 4040 because if the counters Q4 output remains on then so will the LED. To get around this, a 555 monostable is used which turns on the LED for a brief amount of time when the trigger pin is pulsed. Therefore, even if Q4 remains on, the monostable remains off once C2 charges.
All the CNC files can be found in the project folder and include all the needed G-Code for a CNC 3020 (also included is auto leveled code).
Once the circuit has been built, it would not be a bad idea to make the circuit portable by integrating it into a box, adding a portable power supply (such as a battery), and adding a switch so that the power can be turned off when not in use.
Graduated from the University Of Warwick in Electronics with a BEng 2:1 and currently runs MitchElectronics.
