ChrisOfBristol
Member
rogs
The bat was back last night and I couldn't hear a thing, so it's time I abandoned the original circuit. I won't mess about just replacing the two 386s with two opamps as you obviously wouldn't have used more than 2 if 2 were enough, although it's possible you only needed three but used all four since there were four in the package. I'll use your circuit as is, although I'll leave the 4024 for the present as that seems to work.
The bat was back last night and I couldn't hear a thing, so it's time I abandoned the original circuit. I won't mess about just replacing the two 386s with two opamps as you obviously wouldn't have used more than 2 if 2 were enough, although it's possible you only needed three but used all four since there were four in the package. I'll use your circuit as is, although I'll leave the 4024 for the present as that seems to work.
Thanks for identifying it, I'll make a note.This is the HEF4017 I used : **broken link removed**
Not all versions have a Schmitt trigger on the clock input. I found it made a 'cleaner' divide by 10 division of the 40KHz signal - especially as the ambient state is at the half rail voltage od the opamp output. Bit unconventional, but it's simple and it works.
I've found what looks like a buzzer, probably from a PC. I think it has a 30-40 Ohm coil so I might have to buy a piezo sounder. I think that's much better than the earpiece although I'll leave the jack socket for the voice recorder and add a potential divider for it.Again, driving the output of the 4017 directly into the output transducer required the use of a high impedance AC piezo buzzer, rather than a low impedance speaker or earpiece. The 4017 probably doesn't have enough drive capacity to make a useful noise from a low impedance device.
Since I've got a TL074 I'll use that. I could replace it if the battery goes flat too quickly.Don't use the 74HC4017 version unless you are using a 5V DC supply. The one I linked to can cope with a 3-18 V supply.
The TL074 will be a better choice, spec wise, but will draw a lot more current (relatively speaking)
Nigel has suggested a circuit too, but I'll leave heterodynes for later.I do have a (relatively!) simple circuit for a heterodyne version as well if you'd like me to dig that out. You will need a better transducer though.
Shall note for later.Farnell do one: https://uk.farnell.com/knowles-acoust...4/dp/1367846RL but it's not cheap!!
Not actually tried one out (yet!), but it's a much better spec than the electret capsules I was using.
If you do get your freq div one working well, you'll want to try a heterodyne!
I think that the idea is that you record the sound then play it back later slowly, so you hear what it actually sounds like apart from being slower. I suppose with a hetorodyne you miss a bit because it is so fast. Some computer sounds cards will record at a sample rate of 96KHz so it might be possible to use one of those on a laptop and software like Audacity to record it. For higher frequencies it might be possible to build/buy an analogue/digital converter with a higher sample rate to plug into the laptop USB socket.I would love to go the whole hog, and do a 'real time' one, without paying the 'research' type prices the commercial units cost. Some of the audio recorders like this one: **broken link removed** look promising --especially if use with the transducer I suggested above.
You'd still need a freq div or heterodyne to find them though!!
But we are talking real money now.........
I think this sort of thing should be researched more - we might find that animal communication is a lot more sophisticated than we think.Your last point.. must be something like that, but think of the difference in levels. Listening for your own attenuated 'echo', while ignoring direct ultrasonic 'blasts' from other nearby bats which would be many times 'louder' than you own echoes.......quite remarkable....
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