BattyBirdNet-Pi

Its 7 or 8 years since I last did any bat monitoring.

 

To be honest, I got a bit bored with it.

But now I've set up a BattyBirdNet-Pi system ...I'm back!

Electret Microphone Preamplifier

This design runs from a 5Volt USB supply and attempts to minimise electrical noise.

I wanted to create a simple preamp for an electret mic insert using components from my bits box.

So component values and transistor types are not critical.

DodoPi Bat Recorder: "hey, we have a live one!"

Bats flying around in mid-winter! ...whatever next?

It may be relatively rare compared to the number of recordings made each night during the summer...

...but just one recording shows that there are bats out there.

Gambas Bat Recording Software for the UltraMic + Pi 3

As soon as Christmas was behind me, I found some time to progress my bat detector project.

I've been running the Dodotronic UltraMic with a Raspberry Pi 3 using re-written Gambas code...

...but the problem at the moment is a distinct lack of bats.

the Dodotronic UltraMic: first impressions

I just splashed out £225 on this USB microphone.

Initially I just plan to experiment & compare it with my home-made analogue bat recorder.

If all goes well this may turn into yet another bat detector/logger project.

Bats, Hogs & Hibernation

I used to think that 'hibernation' meant 'sleeping through the winter' in the sense that an animal went to sleep in November and woke up at the end of March.

Maybe this is why my tortoise died.

I stuck him in a cardboard box when I was 7, and only went back to wake him up in April.

BatGuru: a British bat ID helper

My BatGuru is a program written in Gambas which helps me identify British bat species based upon echolocation call data.

It simply saves me having to juggle the key parameters in my head as I scan the charts in my reference book.

But identifying bats from their calls is tricky due to the wide variability of their calls.

Common Pipistrelle Feeding Buzz

Bat echolocation is all about catching a meal.

After all, if bats could safely feed during the day, they wouldn't bother to stumble around in the dark of night. 

So its good to catch the occasional ultrasonic recording of bats catching their prey.

Bat Call Logger: more on call analysis

Following my last post I have had some time to analyse a few more bat recordings and consider how to streamline my work flow.

Until recently, I've been carrying out all file operations using Audacity.

But there are a few things I can do via the command line, which I've pulled together in a Gambas GUI program.

Bat Call Logger: full-spectrum analysis

With the recent step change in the weather, I was able to run the system last night and capture bat calls for the first time this year.

It looks like my modifications to the system are paying off.

I'm now getting full-spectrum (ultrasonic) recordings which are much easier to analyse than the previously used Frequency Division recordings.

Bat Camera: just a wild idea!

What if I triggered a camera from my bat detector?

I'm not looking for prize winning bat photos, just a possible aid to identification.

Would the system capture anything recognisable?

Bat Call Logger: implementing pre-capture

My bat call logger uses a very simple/crude means to trigger recording.

This seems to work, but a few recordings are blank, as if the triggering signal has stopped before the recorder kicked in.

By having a pre-capture function, I should be able to capture a sequence before the trigger takes affect.

Bat Call Logger: Wolfson audio card frequency response

Having got my Wolfson Audio card working happily with a Raspberry Pi 2, I decided to try and check the frequency response.

As this card is described as a 'audio card' and the only figures I've seen relate to the audible range, I didn't have high expectations regarding its use in my Bat Call Logger.

Anyway, to find the answer, it was just a question of setting up some test gear and running a few checks.

Bat Call Logger: recording ultrasound

My bat project has been on the back-burner for the last few months, as I understand that bats don't venture out much during the winter.

However, the Weather Man on BBC's Winterwatch did say he had seen them flying around on a few mild evenings during January!

So maybe its time to do a bit more work on my Bat Call Logger and check if there are any out there.

Bat Call Analysis: second thoughts

I'm still trying to reconcile my bat call recordings with the data provided in the Jon Russ book "British Bat Calls".

This caused me to question whether my home-brew bat detector was a reliable witness.

Just how much faith can I have that my FD detector is producing sensible recordings?

Bat Call Analysis: more difficult than it looks!

So I've now got a few hundred recordings from my Bat Logger, collected over a number of nights.

Time to settle down with Audacity and a pint of IPA, and analyse a bunch of waveforms.

Identifying the bat in question is easy, right? Its just a matter of determining frequency, repetition rate...

Bat Call Logger: the hardware

My bat call logger combines a frequency division bat detector with a Pi based audio recorder.

Recordings are simply triggered by a short stream of pulses from the detector (i.e. "activity").

Having spent a bit of time trying to optimise the hardware, I now need to document what I've done, before I forget why I've done it!

Bat Detector: automatic recording

Following on from my last post, this one gives revised details of my Pi based automatic recording system.

My original software just didn't work with real bat calls, and the microphone didn't have a very good response at high frequencies. 

But now this has been sorted out I'm getting 10-20 recordings per hour!

Bat Detector: electret microphones

Building your own Bat Detector is a relatively easy electronics construction project.

The tricky bit can be locating a suitable transducer or microphone that has a useful frequency response into the ultrasonic range used by common bats.

During the last few weeks I have been testing a number of devices, and here are my notes.

Bat Detector Overhaul: Portable Field Unit

Sooner or later I'm going to have to accept that the bats are not coming to me, so I need to get out and find them!

I could do that now just using the hand-held bat detector. But I'm thinking it would be nice to test the whole automatic design illustrated in an earlier post.

So I've put together a rough outline schematic and started collecting bits & pieces.