How to get 1.5Volts from a microphone.

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I have cobbled together several devices for triggering remote cameras, based
on a Passive Infrared Receiver.
Briefly, the PIR, which is designed to sense a passer-by and turn on six
white LEDs for a few seconds to illuminate a stairway or whatever, has one
of the LEDs replaced with a connection to an analogue-to-digital input of a
Picaxe. The Picaxe program waits until the passer-by (in this case a wild
lyrebird singing and displaying on his performance mound ) triggers the PIR
and takes photographs every five seconds for one minute. After the minute,
the Picaxe program tries again, the assumption being that if the bird is
still performing, the PIR will pick him up again.
Not so. What happens is that the bird stands stock still for up to twenty
minutes and doesn't trigger the PIR again until he leaves. Our only
photographic record of his memorabloe performance is the first minute after
he arrives, and a brief shot of his retreating backside as he leaves.
But all the time he is there he is singing, and deafeningly. So what I need
is a signal from a microphone. I have programmed  the Picaxe to recognise a
level, however fleeting, of 1.5Volts from the PIR, and I'd like to add to
the existing setup a similar, ~1.5Volts from a microphone. Just a voltage.
No attempt to reproduce the actual sound. I would need some kind of level
control, in order to adjust the output to respond to the target bird's
close-up song and not respond to his rivals who are some distance away and
nowhere near as loud.
I have looked at a kit for a voice-controlled microphone which would
probably work but needs 12Volts worth of batteries. I need at least four of
these devices and possibly eight, so they must be cheap. I feel that there
must be a simple way to achieve this. On past experience, if there is a
simple answer, this is the newsgroup where I will find it.
Can anyone help?



Re: How to get 1.5Volts from a microphone.


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Why not just have to camera trigger for 20 minutes instead of 1 minute then?
Storage is cheap...

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You'll have to experiment a bit and figure out what levels you get out of
your electret mic, and what the background levels are.
That will require some form of data logging capture of the actual audio
levels (or waveforms) so you'll have some reference levels to work from for
your final solution. That starts getting a bit messy and potentially
unreliable I suspect. This solution doesn't give good vibes...
You might get better background sound discrimination with a directional
shotgun mic.

I'd just shoot images for longer using your existing setup and sort through
the images later.

Silly question, but if you want to capture the bird "performing", wouldn't a
video camera be a better option?
i.e. if the bird is just sitting their "stock still" as you say (singing?),
what's the point getting that on still camera?

Dave.
--
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Check out my Electronics Engineering Video Blog & Podcast:
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Re: How to get 1.5Volts from a microphone.



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................. He can come for a couple of minutes or for up to twenty.
..................The warmth of the sun reflecting off the clay, interrupted
by moving branches, gives two or three false triggers each session.
..................The camera batteries will last for up to seven hours while
waiting, but will run out after less than an hour and a half of shooting.
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.................The cameras' CF cards are limited to 2Gig.

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...........................The Mics will be directional.
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..........................On any given day, we will have six to eight mounds
staked out.
...........................On most days he won't perform where we want him.
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.......................We have eight Canon G2 cameras. Most were bought on
eBay for about $150 each. Video cameras are too expensive. (YET. Maybe in a
year or so).
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................. Sorry, a bit of hyperbole there. He is displaying his
amazing tail feathers in a most photogenic series of poses.
..................His warm, infrared-emitting body is not moving enough to
affect the PIR.
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Re: How to get 1.5Volts from a microphone.




   You could always a microwave or ultrasonic doppler sensor instead of
a PIR, alternatively the better quality PIR's had different Fresnel lenses
for the front for different applications: longer range/better gain.

    It may well be that a really cheap PIR is better suited as it won't
tune out the lyrebird as background noise.

Re: How to get 1.5Volts from a microphone.


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No matter what quality of lens the PIR only triggers if there is
movement - then bird standing still and singing won't qualify.

Re: How to get 1.5Volts from a microphone.



David Eather wrote:
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   How about one of the rare tap dancing birds? ;-)


--
You can't have a sense of humor, if you have no sense!

Re: How to get 1.5Volts from a microphone.


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A PIR Fresnel lens assembly is comprised of smaller lenses, it's
possible to buy different types that trade off range with the amount
of movement detected: If you fitted a lens with many more smaller
lenses in it, the range suffers but it will now trigger with only
slight sideways movements as the IR light from the bird is focussed
onto the sensor by different parts of the array.

     With the right lens the bird would have to be totally stock still
to avoid detection.

Re: How to get 1.5Volts from a microphone.



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Using sound detection here is an interesting problem that I've dealt with
several times in other scenarios. Just measuring level is likely to result
in a spurious trigger rate that's far too high if the setup is sensitive
enough to detect anything. I'd be considering some processing of the sound
input, as far as I know, Lyre bird song can contain single frequency sounds,
it's easy to pick this with a small microprocessor these days, with fast
fourier processing. It would require someone with micro programming skills,
however there's tons of FFT code googleable. Bird song whistle will show as
a clear spike in a data array that will stand out from typical background
noise in a bush environment, which will be mostly white noise or close to
it. You wouldn't need to know the frequency, just that there was one or a
few isolated frequencies present which are significantly above the
background.

I'd get a recording of the sort of thing you expect, and use that to test
the algorithm.

 Sorry if that all sounds high-tech, but I believe it could be a viable
solution.



Re: How to get 1.5Volts from a microphone.


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How about a notch filter tuned to the bird's frequency? - simple, cheap
and plenty of info on how available on the net.

Re: How to get 1.5Volts from a microphone.


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Have you tried motion dection using using the camera?
http://chdk.wikia.com/wiki/CHDK

Dave.

--
================================================
Check out my Electronics Engineering Video Blog & Podcast:
We've slightly trimmed the long signature. Click to see the full one.
Re: How to get 1.5Volts from a microphone.



snip>
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....................Alas, this so0ftware works on Canon G7 and G9.
....................Our cameras are Canon G2, which are seven? years old.
.....................When we were capturing images to laptops. we used
ZoneAlarm, with limited success.
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