bat detector

[captaincaveman]

hi again, has anyone got a schematic for construction of a bat detector, this is the next project i'd like to get into and never done anything with detecting ultrasonics before

any help would be appreciated

thanks

 

[ClydeCrashKop]

Digikey has a card type piezo speaker that is good for 100 kHz. Would it work as a microphone? Is bat sonar higher frequency than that?

 

[dknguyen]

The range frequencies that a bat can emit depends on the species (an individual can tune it's frequency between a certain range). If I remember right 100kHz would be a frequency that the bat uses when it is near it's target and requires more accurate sensing of the target. I would choose a lower frequency range to get the long-range navigational echoes. I would find something able to detect a range of frequencies...since you might not get any bats if you go with one frequency since they themselves use a range that varies from species to species.

EDIT: "frequency echolocation calls produced by bats range from 20-200 kilohertz (kHz) or more "

Whew, quite a range huh? A bat's echolocation transmitter pretty much kicks the ass of every man made transmitter, and their receivers? Well if you read up on what they can do with echolocation (even their multi-frequency transmittion/reception capability is amazing, and they use this to account for the doppler effect as they fly!). Comparing human made ultrasonics to bat echolocation is like comparing stones to ballistic missiles.

I mean if you ever used sonar you'd find that the resolution on 120kHz sonar is 15cm or something from a few feet away and useless beyond that. Comparitively, a bat can tune it ultrasonic frequency (amazing in it's own right) to account for the doppler effect (even more amazing) and the range of the target to get the most precision. And then, it can interpret a 120kHz echo so well that it can achieve the resolution required to pinpoint a moth- try doing that with human 120kHz sonar with a lousy resolution measured in the cm! It's like using a magnifying glass as a microscope...and having it work! I'm still not quite sure how they seem to increase the resolution of an ultrasonic wave by so much (but then again, neither are researchers).

 

[dknguyen]

"The pipistrelle is the first bat you are likely to come across, and these are usually listened for with the bat detector set to 50kHz. There are three types of pipistrelle in the UK, but fortunately for bat workers, they have different 'best listening' frequencies, one at 45kHz and the other at 55kHz. The rarer Nathusius pipistrelle echolocates at about 37kHz. Pipistrelles usually sound like irregular 'smacks' that tend to vary in the pitch and are at a medium repetition rate.

The noctule is entirely different, and is usually best heard with the detector set to 20 to 25kHz. The sounds from the bat detector are usually alternate 'smacks' and 'tocks' at a fairly slow repetition rate which together sounds like a fairly irregular 'chip-chop'.

The Myotis bats like the Daubenton's bat, all sound rather similar, generally coming out as a series of 'clicks' when listened to with the bat detector set to 45 to 50 kHz. The Daubenton's, Whiskered and Brandt's bats have fast repetition rates but the Natterer's bat tends to be even faster, quieter and more irregular. The long-eared bats have a similar sound to the Myotis species, but at a faster repetition rate, and are so quiet that they are generally nearly impossible to pick up.

Perhaps the most unusual sound from bats in the UK are from the horseshoe bats. These use a constant frequency call and rely more on doppler effects for their echolocation. These sound like a warble on a heterodyne bat detector with the greater horseshoe being best heard at around 80kHz and the lesser horseshoe at 115kHz. "

 

[dknguyen]

Some basic bat detectors (conceptual, not circuit schematics):
https://njsas.org/projects/bat_detector/

 

[Roff]

Did you try Googling "bat detector schematic"?. I got several hits.

 

[captaincaveman]

Did you try Googling "bat detector schematic"?. I got several hits.

thanks for all the help guys, never thought to google(how obvious is that )

heres a couple i found

**broken link removed**

https://njsas.org/projects/bat_detector/populel_sch.html

**broken link removed**


just have to decide which one to use now

thanks again guys, loads of quick responses on here

 

[jjw]

This is a good page: https://bertrik.sikken.nl/bat/index.html

I have built the heterodyne detectors NE612 and BD4066 ( the correct link is: **broken link removed** )
I simplified the BD4066 detector by omitting two amplifier transistors and using one inverter as 180 degree phase shifter before the switching mixer and used electret microphone in place of the ultrasound transducer.