Wednesday, July 21, 2021

A DIY Ultrasonic Microphone For The AnaBat Walkabout

A DIY Ultrasonic Microphone For The AnaBat Walkabout from Titley

Below, I describe some details of my experiences:

I've tried making some DIY-type ultrasonic Mics, to plug into The Walkabout's 2.5mm microphone jack... However, there are a few reasons why I wasn't successful. Without going into a bunch of (unnecessary) technical details, suffice it to say that The Walkabout's Mic jack is a bit too advanced to "suffer the foolishness" of my amateur attempts!

The Walkabout's jack provides approx. 6.4 v DC - Not suitable for most DIY Mic capsules, etc. This equated to more tinkering.

Here is just one (of several!) examples, of a (home-built) ultrasonic microphone; which I wired to a (male) 2.5mm plug, for testing with The Walkabout.

The photos below, show a quick wiring-up, for testing. A DIY Mic utilizing the Panasonic WM-61A Mic capsule.

Quick wiring-up
Panasonic WM-61A


Here is another Mic, which I initially thought would be perfect for The Walkabout. It is an adorable little circuit board (complete with Mic capsule already attached).

Prior to attaching Arduino-type pins
AA battery shown for scale

These are available from FEL Communications Ltd. (in UK).

In order to get the output voltage of The Walkabout's (2.5mm) jack, to a safe and usable level for the Micbooster Mic board: 

I found that a 180K Ohm resistor (on the [+] voltage wire) reduced the voltage from 6.4v to 4.6v - Which is acceptable for the Micbooster ultrasonic board (voltage must be kept below 5v when working with this board).
However, I still had no success in recording any bats through it (attached to The Walkabout). All of my early attempts/tests, with DIY microphones, were unsuccessful.
It was fun trying though. And I was thankful that The Walkabout gives one the opportunity to experiment with such external microphones.

Experiments involving The AnaBat Walkabout have ceased. There is a limit to how much (careful) experimenting I'm wiling to do on a high-end bat detector. Especially one generously loaned to me for testing and review.

I eventually came to the conclusion, that it would be best for someone to just purchase the official Titley microphone adapter and Mic, if there is a need.

In my case, while spending a lot of time trying to build a working Mic:
It only served to bolster my appreciation of the quality recordings captured with The Walkabout's built-in (Knowles) microphone. 

But, experiments with this cute little (Micbooster) Mic board continue...
Recent tests, involving the ultrasonic mic board and regular digital recorders seem promising.

Happy bat detecting!

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