Bats

[j0e_bl0ggs (deceased)]

Well, had a little peace this morning so assembled this kit quickly.
A simple Bat detector!



Populated with parts



Test drive tonight as the Bats are around [Pipistrellus pipistrellus].
Will be a nice educational tool for some young tearaways that I know...

[JaDub]

OK,   I give..............     a BAT detector ??   I  can see having  a bat attractor.    ???????

[gitano]

Very COOL!

I see "REC1". What are you using and where did you get it? Do you know the frequency response curve for it? I suppose that the FRC is relatively immaterial if 'detection' is all that is desired and the receiver's response includes the bat's primary frequency somewhere in the FRC. But... It's simply my 'nature' to look at FRCs because they so influence the "data". Even when only one only wants 'detection'.

Been a long time since I proto-boarded any circuits. It's great fun. As I think of it, this device could have applications in my house. Each fall we get little brown bats (Myotis lucifugus) passing through on southerly migrations. I can't hear their calls, but my daughter can. They find their way into my house, and I am often asked, "Did you hear that?" (Knowing that it is the sound of a bat, there is a certain elevated 'strain' in the voice of the inquirer.) Ihave to say - honestly - "No". Those frequencies are long gone from my FRC.

Anyway, again, cool!

Paul

[j0e_bl0ggs (deceased)]

Have the article with some response graphs regarding the transducer and filter spec, will send it to you when next at work!

[j0e_bl0ggs (deceased)]

You want to tell your daughter enjoy being able to hear bats, it will not last for long!

[drinksgin (deceased)]

Yep, my wife finally stopped hearing them at about 45, though I still maintain the sounds she heard were in her mind, not from some little furry critter.
I never heard many highs, but I can hear thunder as much as an hour before other people.
An audio chart showed my 50 cps threshold at  - 80 db, but + 60 db at 5000 cps.
Talk about a steep curve!

[j0e_bl0ggs (deceased)]

Well successful bat detection, think I'll build a 'hetrodyne' type next!

[gitano]

Without tracing the signal processing, I assumed you were "converting" the detected signal to something more audible for an old guy with tinnitus. I still assume that until you tell me otherwise, which of course is not necessarily heterodyning. Are you going to heterodyne because you want to record the bat "call"?

Heterodyning - for those that my not know - is a way to convert one signal (frequency) to another by mixing the "wild" signal with a known one. So for the bat example, let's say the bat is producing a sound somewhere in the 14,000 Herz (cycles per second) range, but 'you' can only hear sounds below 10,000 Herz and you would like to hear/record the 'characteristics' of the bat's call. You would have ONE input to your "mixer" (heterodyne IC) be a sine wave of 10,000 Herz, and the OTHER input would be the sound from the bat at something around 14,000 Herz. When these two frequencies are combined, they produce two results: 1) A "sum" output that would be about 24,000 Herz (14,000 + 10,000), and a "difference" output of about 4,000 Herz (14,000 - 10,000). While the output frequency would be shifted to your audio band, the "character" of the bat's call - "chirps", "whistles", click-trains, etc., would be preserved but audible because they had been frequency-shifted down to your audio range.

I looked at this http://pw1.netcom.com/~t-rex/ and see why you are using the 4024.

Personally, I kinda like the analog domain even though you might have to "tune" it for certain specific responses.

Paul

[recoil junky]

Had a bat in the bedroom t'other night. I told her to get  back on her broom and fly back out too.

JUST KIDDING!!!

No really there was one flew in the open sliding glass door and t'missus hid under the covers until I caught it and released it ALIVE back outside. Cute little brown bat. Madder'n a wet hen though.

RJ

[j0e_bl0ggs (deceased)]

Having never been able to hear 45kHz...

The detector is a simple frequency divider so the 'audio' output is just like a Geiger counter - a series of clicks - one pulse out of every sixteen is what we hear so lots of info is missing!

The heterodyne [basically what we know as a radio] will have the bandwidth to give us some idea of the bats call and fill in the blanks as Paul said.

[j0e_bl0ggs (deceased)]

Had a bat in the bedroom t'other night. I told her to get  back on her broom and fly back out too.

Been there!

[recoil junky]

I've been on graveyard shift the past couple of nights getting to watch bats fly around the light plants catching moths while waiting to get loaded. Very fascinating.

RJ