BACKGROUND:
It's time to think "outside the box" ... this module can be much more than a "Bat Detector"
This "kitset" may hold some interest for those who like to experiment or discover the world of ultrasonic sounds, both from living creatures and equipment such as motors etc. My interest was as a custom test instrument so that I could listen to motor bearing noise (often way above the normal audible frequency range for humans) and at times it came in handy locating high voltage arcing, without having to turn the lights off! Instead of seeing and smelling the ozone odour, I could hear the arcing taking place. I actually modified one of these kitsets slightly to suit my purposes, nothing dramatic, but I created a tube arrangement which sat on the front of the microphone to act as a "sound waves" focus. The native angle of response of these ultrasonic transducers is around 30 degrees and I wanted to narrow it down a bit.
Oh, I forgot ... you can listen to "bat sounds" if that is your thing (we have thousands of bats around Western Sydney in the warmer months and I had no desire to listen to their constant screeching!)
Actually I began to become interested in listening to "bird sounds" a while back, but not bats. We have a cockatiel and when it demands attention, the bird "shrieks" when it wants something such as "put me outside with my friends" (the wild birds). I found with this detector that the cockatiel was creating human audible sounds AND ultrasonic sounds when it did this shrieking. Outside with its "wild mates" it continued to use audible (to humans) sounds plus ultrasonic "noises" ... I think this is why when we stream a video on Youtube for our bird, it doesn't react anywhere near as much as when it is placed in the backyard and it then begins talking to other "real" birds. The streamed video would have the ultrasonic sounds "filtered out" by the digital streaming process, so it could be like our bird was listening to another bird who wasn't producing the "right sounds" and it was therefore quite disinterested in striking up a conversation with that bird.
I may well pursue this little adventure into the world of bird communications with my other unit, if ever I get some spare time (I need a time machine, that works!) Perhaps others may come up with even more interesting ideas to use this type of detector for?
This kitset is almost completely assembled when supplied, nice SMD based main board and it is basically just a case of plugging in the correct connectors and you are in business!
This is a quality designed product which is intended for those who have an understanding of electronic principles so that you can understand how this works and this is evidenced by the well written booklet (not Chinglish) which explains ultrasonic sound waves in detail, the operating principles of this detector and even supplies a full schematic diagram and board layout diagram.
Designed in United Kingdom, the functioning of this detector revolves around the clever use of a CD2003 LSI, this chip is actually a single chip AM/FM radio. The design of this detector works by mixing the ultrasonic sound waves detected by the microphone with a local oscillator signal (555 timer chip is used here), producing a beat signal. This signal is then sent to a common LM386 low power audio amplifier.
Just two user controls, the volume and a control of the "beat frequency"
Now I was working around the 40Khz region so this transducer suited my purposes fine (roughly 38KHz ~ 45KHz 3dB points) but if you were going to take a listen on much higher frequencies, say 100KHz or above then another transducer would need to be found - this one just isn't designed for those higher frequencies. This would particularly apply if listening to some animals which emit ultrasonic sound waves as a means for communication, often way above 40KHz
This is what attracted me to this kitset, there was a time when I wanted to investigate some ultrasonic "noise" and this kit fits the bill perfectly. I actually had two of these kits, one was shifted to a "proper" metal enclosure once I had checked that the detector would suit my purposes ... I have kept that unit.
Seems almost criminal to call this a "kitset" ... there are no "spring connections" nor soldering required, plug in 4x sets of connectors and you are in business!
This kit set is the "spare one" that I originally imported from UK (more cost effective shipping to send two) that I have opened, connected the speaker, battery & transducer to the main board to ensure it is working properly and then, as all was well, I have re-boxed it as I had no need for this second unit.
EIGHT Innovation Ltd - Build Your Own Bat Detector
Conceived & designed in United Kingdom
Manufactured in China
Product code: EBD2766
Comes with all components to put together a compact ultrasonic sound wave detector or receiver. Not really a kitset as the main board is fully constructed and it is just a matter or interconnecting the audio output to the 2" diameter loudspeaker, the battery lead (with 9V battery clip fitted) and the "push on" gold plated connectors for the ultrasonic transducer. Putting the kit together takes perhaps 10 seconds and there is no need for soldering, just a bit of pushing when fitting the plugs into the keyed sockets on the main board - easy! Of course there is also a small packet containing the two control knobs along with the washer and nut for the pots.
Runs off a standard 9V alkaline battery
The volume control also has the ON-OFF switch
CUSTOMISING HINTS:
I took this basic unit and modified it to suit my purposes, nothing drastic but it just suited me better. I placed my unit into an all metal enclosure and allowed for the input of an external DC power source in addition to the existing internal battery.
I did the same with the audio output, while the internal speaker and LM386 audio level is "acceptable", I wanted to have more volume so I enabled the audio to be fed into an external portable amplifier via a 3.5mm socket.
I also wished to narrow the angle of the ultrasonic microphone field, which is typically 30 degrees. This was just a mechanical modification using a tube fitted over the face of the microphone to make the microphone much more directional. I left the current arrangement of Gold plated pin sockets to the microphone alone, they are actually really convenient when testing different transducers at the front end.
TESTING:
While this particular unit was opened, I never used it as such ... but to be sure all is ok, I connected all the components and made some simple tests.
Powers up fine (with my test battery measuring 9.2V, the quiescent current measures 17mA)
No strange noises when there is no ultrasonic sound waves detected, not even a hiss!
Best "quick and nasty" way to test this was to rub my fingers together in front of the transducer ... all good here and I could hear my finger rubbing even at a reasonable distance away - not bad because we are talking very, very low level ultrasonic sound waves in this test situation.
I am satisfied that all is well with this unit and have placed all the components back inside the original inner box (still interconnected for convenience) but with the transducer disconnected and packed in bubblewrap along with the knobs etc in another small packet. This is all inserted inside the original outer box and then within sealed clear plastic to keep everything clean and dust free.
