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'[PICLIST] [OT] Sound Detector'
2000\12\22@055828 by Henry Low

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Hi all,
   Seasons Greetings.
   I was thinking of implementing beacons in a robot testing arena that
emits sonar signals or a buzzy sound for the robot to move towards. And the
beacon will be turned off upon sensing the robot's presence (which means the
beacon has got it's own sensor too). My aim is to see how fast the robot is
able to disable say 10 beacons in a reasonable robot testing ground. Is this
idea feasible?? How can I make the robot move closer to the buzzy sound (can
be modulated)?? Does it involve a complicated algorithm for it's decision to
move towards the beacon?? Any help, comments are most welcome.

Regards,
Henry

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2000\12\23@002306 by James Burkart

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       What about using a strobe light instead of a sound? Mount two CdS photo
cells facing the same way (eyes for the robot), and put a card between them.
Design a circuit to compare the difference of light levels between the
detectors. When the levels are equal you are facing the strobe. An easy way
to compare the input from the CdS's is to use an op-amp as a comparator.
It's sooo much easier to measure the difference between light levels than it
is to measure sound. I suppose that if you were to stay with the sound
instead of using light you might want to use a similar method to direct your
robot.

James Burkart

{Original Message removed}

2000\12\23@013911 by Henry Low

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Hi James,
   Thanks for your suggestion. I wonder if the strobe light will false
trigger my IR sensors?? I am using a photodiode together with an IR LED for
short range object detection. But this idea is very feasible. Thanks a lot.

Henry

----- Original Message -----
From: "James Burkart" <.....grafxjkbKILLspamspam@spam@PACBELL.NET>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Saturday, December 23, 2000 1:12 PM
Subject: Re: [OT] Sound Detector


>         What about using a strobe light instead of a sound? Mount two CdS
photo
> cells facing the same way (eyes for the robot), and put a card between
them.
> Design a circuit to compare the difference of light levels between the
> detectors. When the levels are equal you are facing the strobe. An easy
way
> to compare the input from the CdS's is to use an op-amp as a comparator.
> It's sooo much easier to measure the difference between light levels than
it
> is to measure sound. I suppose that if you were to stay with the sound
> instead of using light you might want to use a similar method to direct
your
> robot.
>
> James Burkart
>
> {Original Message removed}

2000\12\27@004740 by Henry Low

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hi james and everyone,
   I wonder if the strobe light will false trigger my IR sensors and
prevent my robot from getting close to it?? Is the strobe light just a
normal LED?? I am not too sure how to generate this strobe light. My IR
sensor module consists of an IR emitter and a receiver (i am using a
photodiode). Isn't the photodiode sensitive also to the strobe light?? or
any normal LED shining directly at it??
   Hope to hear from you soon.

Henry

----- Original Message -----
From: "James Burkart" <.....grafxjkbKILLspamspam.....PACBELL.NET>
To: <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Saturday, December 23, 2000 1:12 PM
Subject: Re: [OT] Sound Detector


>         What about using a strobe light instead of a sound? Mount two CdS
photo
> cells facing the same way (eyes for the robot), and put a card between
them.
> Design a circuit to compare the difference of light levels between the
> detectors. When the levels are equal you are facing the strobe. An easy
way
> to compare the input from the CdS's is to use an op-amp as a comparator.
> It's sooo much easier to measure the difference between light levels than
it
> is to measure sound. I suppose that if you were to stay with the sound
> instead of using light you might want to use a similar method to direct
your
> robot.
>
> James Burkart
>
> {Original Message removed}

2000\12\27@034108 by James Burkart

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  Well, If you use something like a super-bright blue or white LED the
spectrum they emit is very narrow, no IR. But I really don't think that they
are bright enough.
  The light emitted by the "beacon" would ideally be diffused or at least a
wider dispersion than the calumniated beam of an LED. The best light source
should be an incandescent bulb. They do produce a lot of IR, but the IR LED
would be much brighter in comparison. You could also do some things to make
the IR sensor less sensative to the "beacon", like a filter of some kind.
  Have you thought of using some kind of sonar for the collision detector
instead of IR? Jameco has a kit that might be able to be adapted. It's the
kind of thing that is used in newer cars to let you know if you are too
close to something. It would be easier to use "sonar" this way, then to use
it to home in on a specific something.

James

{Original Message removed}

2000\12\27@063346 by Henry Low

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HI James and everyone, thanks for the prompt reply. I am using both sonar
and IR for my collision detection. Is it advisable to have sonar sensor as
its only form of detection??
Anyway, do u know what the photodiode reacts to?? Normal light or IR?? It is
an important point for me.

----- Original Message -----
From: "James Burkart" <grafxjkbspamspam_OUTPACBELL.NET>
To: <@spam@PICLISTKILLspamspamMITVMA.MIT.EDU>
Sent: Wednesday, December 27, 2000 4:37 PM
Subject: Re: [OT] Sound Detector


>    Well, If you use something like a super-bright blue or white LED the
> spectrum they emit is very narrow, no IR. But I really don't think that
they
> are bright enough.
>    The light emitted by the "beacon" would ideally be diffused or at least
a
> wider dispersion than the calumniated beam of an LED. The best light
source
> should be an incandescent bulb. They do produce a lot of IR, but the IR
LED
> would be much brighter in comparison. You could also do some things to
make
> the IR sensor less sensative to the "beacon", like a filter of some kind.
>    Have you thought of using some kind of sonar for the collision detector
> instead of IR? Jameco has a kit that might be able to be adapted. It's the
> kind of thing that is used in newer cars to let you know if you are too
> close to something. It would be easier to use "sonar" this way, then to
use
> it to home in on a specific something.
>
> James
>
> {Original Message removed}

2000\12\27@070121 by Roman Black

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Henry Low wrote:
>
> HI James and everyone, thanks for the prompt reply. I am using both sonar
> and IR for my collision detection. Is it advisable to have sonar sensor as
> its only form of detection??
> Anyway, do u know what the photodiode reacts to?? Normal light or IR?? It is
> an important point for me.


Hi Henry, good to see you got the photodiode
trans/receive pair working ok. The photodiode
type you have responds MAINLY to IR, but remember
that includes sunlight and some heat sources.

To get reliable IR you need to modulate it,
and sense for that modulated frequency with
the photodiode. There are many sources of info
on the web that already have circuits and pictures
and may be a quicker source of info for you than
the piclist.

Try doing a Yahoo.com search for "robot infrared"
:o)
-Roman

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'[PICLIST] [OT] Sound Detector'
2001\01\02@065324 by Michael Rigby-Jones
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> -----Original Message-----
> From: James Burkart [SMTP:RemoveMEgrafxjkbTakeThisOuTspamPACBELL.NET]
> Sent: Wednesday, December 27, 2000 8:38 AM
> To:   spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU
> Subject:      Re: [OT] Sound Detector
>
>    Well, If you use something like a super-bright blue or white LED the
> spectrum they emit is very narrow, no IR. But I really don't think that
> they
> are bright enough.
>
Surely a white LED, by definition, does not have a narrow specturm?

Mike

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2001\01\02@085515 by mike

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On Tue, 2 Jan 2001 11:51:55 -0000, you wrote:

>> -----Original Message-----
>> From: James Burkart [SMTP:TakeThisOuTgrafxjkbEraseMEspamspam_OUTPACBELL.NET]
>> Sent: Wednesday, December 27, 2000 8:38 AM
>> To:   RemoveMEPICLISTspamTakeThisOuTMITVMA.MIT.EDU
>> Subject:      Re: [OT] Sound Detector
>>
>>    Well, If you use something like a super-bright blue or white LED the
>> spectrum they emit is very narrow, no IR. But I really don't think that
>> they
>> are bright enough.
>>
>Surely a white LED, by definition, does not have a narrow specturm?
Not narrow, but spiky - white LEDs are blue LEDs with a phosphor to
convert some of the blue to yellowish, so the output spectrum can be
rather uneven.
..having said that, I've just shone a white LED at  reflective
diffraction grating (otherwise known as a CD!), and at the right angle
you do see most of the colours of the visible spectrum with no obvious
colour banding.
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2001\01\02@232941 by James Burkart

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Yes, it is very narrow as compared to an incandescent bulb. A white LED is
not what you would call a true white light. It doesn't emit anything even
close to the IR spectrum.

----- Original Message -----
From: "Michael Rigby-Jones" <mrjonesEraseMEspam.....NORTELNETWORKS.COM>
To: <EraseMEPICLISTspamMITVMA.MIT.EDU>
Sent: Tuesday, January 02, 2001 3:51 AM
Subject: Re: [OT] Sound Detector


> > {Original Message removed}

2001\01\03@030844 by Michael Rigby-Jones

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> ----- Original Message -----
> From: "Michael Rigby-Jones" <RemoveMEmrjonesEraseMEspamEraseMENORTELNETWORKS.COM>
> To: <RemoveMEPICLISTspam_OUTspamKILLspamMITVMA.MIT.EDU>
> Sent: Tuesday, January 02, 2001 3:51 AM
> Subject: Re: [OT] Sound Detector
>
>
> > > {Original Message removed}

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