The signal from the microphone is filtered to remove interference and amplified then frequency divided using a counter.
Bat detector circuit diagram.
The by far most popular method for bat detectors appears to be the heterodyne down converting if you judge by the number of commercial and home built circuits frequency compression or time lapse this is the most advanced technology based on digital signal processing of the sampled bat sounds but it also requires the most advanced electronics.
This particular bat detector device can be run off 12 volt batteries and be deployed in the wild for days weeks at a time with data being transmitted every now and again via a lora radio link.
Resistors r3 and r4 were selected for high gain in ic1 a.
Firstly such transducers are very responsive to ultrasound and thus produce large output voltages upon detection as compared to a generic audio microphone.
This was first presented by popular electronics magazine as an ultrasound detector in 1994.
Schematic of a heterodyne bat detector.
For the bat detector circuit i didn t design a pcb but soldered the prototype on perfboard.
Schematic and construction the original design concept for this equipment was developed by john errington msc and sylvain frenehard at northumbria university.
The circuit has three stages.
I 3d printed an enclosure for the circuit and two knobs for the volume and frequency control.
Block diagram the block diagram shows the circuit sections for a simple frequency division bat detector.
The circuit diagram in figure 2 shows the complete project and it really is as simple as it looks.
From popular electronics 1994 the circuit shown here is for a heterodyne bat detector.
Recording and analysing bat call audio is a great way to achieve this monitoring especially if it can be fully automated.
The preamp is based on a standard dual opamp and although various types will work i found the tl072 to be the liveliest.
Click image for a larger jpeg view.
Build an enhanced simple bat detector view experiment home built frequency division bat detector view experiment chris eve s bat detector circuit view experiment bat detector circuit with leds to give a visual indication of a bat s presence instead of reproducing the audio at a lower frequency.
Construction is straight forward and can be laid out very much as the schematic shows.
How does the bat detector work.
If you want to design your own you can grab the kicad schematic here and design your own pcb version.
Detection of the high frequency clicks bats emit must be done with an ultrasonic transducer for two reasons.
A preamplifier to boost the signal from the microphone a divider to down convert the frequency of the bat to something we can hear and a power amplifier to drive the loudspeaker.
It has two.
