Alt-BEAM Archive
Message #13484
To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter wilf.rigter@powertech.bc.ca
Date: Sun, 16 Apr 2000 10:40:24 -0700
Subject: PIR detectors - was Re: A reply to Zoz ... and a challenge fo r advanced/bored BEAMers.
Some thoughts on PIR:
deep infrared (PIR) of body heat is close to microwave radiation in
wavelength. The PIR detectors use piezo type sensor devices that are
sensitive only to variations or changes of IR (heat) projected on the
detector surface. All detectors include some form of output buffering to
interface with other circuits. The most common detectors used in household
PIR motion detectors are simple devices with a slow response time and only
small variations in output (+/- 10-100mV) signals which must be amplified.
Some IR detectors have build in gain, filters, and level detector and
generate a logic level output. (
http://www.acroname.com/robotics/parts/R3-PYRO1.html
) Simple detectors use
only one sensor but newer PIR detectors use twin sensors to reject
variations in background IR and/or small targets (animals) using a
differential sensing method. Some PIR detectors use as many as 4 sensors to
reduce erroneous outputs.
The detector sensitivity is greatly enhanced by adding a special freznel
lens which increases the field of vision but more importantly breaks the
image into multiple copies or zones projected on the detector surface. You
can easily observe these multiple projected images by holding a PIR freznel
lens in front of a white surface with a small circle representing the
detector. When an PIR source moves across the field of vision, the freznel
lens causes it's image to move in and out of zones, and even a slow moving
PIR source effectively becomes amplitude modulated (a rapidly pulsating PIR
source) on the sensor. Since the detector is sensitive to change, moving
the detector itself in front of a stationary PIR source has the same effect
as a moving PIR source. If the IR target to be detected is a very bright
broad spectrum IR source (ie a candle, fire) in contrast with a much cooler
background and then the bot can roam or scan for such IR sources. Additional
IR filtering may be required to desensitize the detector to reject
background PIR objects. Alternatively, a simple PIR detector can be used on
a bot for detecting PIR motion but not while the bot is moving. The bot must
be stopped while it takes readings from the PIR detector. Much of the art in
PIR detectors is the design of the freznel lens to concentrate sensitivity
in a zone of vision most likely to contain intruder motion, to accentuate
motion in one plane, and to reject peripheral PIR changes caused by
headlights or small animals.
Special lenses, a tracking head or stereo PIR vision may be a way to sense
PIR motion while the bot itself is moving by canceling changes in background
PIR caused by the moving bot.
wilf
> -----Original Message-----
> From: Bruce Robinson [SMTP:Bruce_Robinson@telus.net]
> Sent: Sunday, April 16, 2000 12:21 AM
> To: beam@sgiblab.sgi.com
> Subject: Re: A reply to Zoz ... and a challenge for advanced/bored
> BEAMers.
>
> Tan wrote:
> >
> > I found This: http://www5.mediagalaxy.co.jp/smm/tech/b_2_5e.html
> > Which is a Pyroelectric Infrared (PIR) Detectors (whatever that is)
> > and can detect body heat, so the specs say.
>
> Very nice, Tan. Thanks.
>
> > Would it be useful to detect human/animal/predator, or would any
> > IR detector do? (Do IR detectors detect heat anyway?)
>
> Yes, with additional circuitry, that's exactly what these are used for
> ... typically in outdoor motion detectors.
>
> IR detectors detect Infrared Radiation, and they detect heat indirectly.
>
> The wavelength of the energy radiated by a hot object is an exact
> function of its temperature -- the higher the temperature, the brighter
> the light. Experienced blacksmiths can tell the temperature of a piece
> of metal to within a few degrees by it's colour. At lower temperatures
> (e.g. body temp), the colour is down in the infra-red range.
>
> The problem with using an ordinary IR detector is that background
> radiation can confuse the detector, which typically measures an average
> temperature. The pyroelectric detector you found responds to a sudden
> change in radiation / temperature. If you walk in front of one, the
> higher temperature of your exposed (or lightly clad) skin moving across
> its field of vision will trigger a response.
>
> Now I need to hack a motion detector and figure out the rest of the
> circuitry :)
>
> Bruce
13485 Sun, 16 Apr 2000 13:44:49 EDT Re: another walker question beam@sgiblab.sgi.com BUDSCOTT@aol.com I just built a walker out of some KTU's, if your willing to sacrifice some
effort, buy a couple of 60 minute kitchen timers and some RM-1 from
solarbotics (more free advertisment). they couple perfectly and cost much
less than a servo!
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13486 Sun, 16 Apr 2000 13:47:06 EDT Re: Solar powered pendulumn project beam@sgiblab.sgi.com BUDSCOTT@aol.com gallileo, i did a report on him in grade school. Man was i a little nerd!
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13487 Sun, 16 Apr 2000 11:44:59 -0600 Re: You guys disappoint me beam@sgiblab.sgi.com Dave Hrynkiw At 10:47 AM 4/16/2000 , JVernonM@aol.com wrote:
>I'm sorry to say, that makes you the fool here. The powers that be don't want
>to hear the truth, they want to talk about building bipeds with only one
>motor and a single 240 chip. Ludicrous you say? Just don't say so out loud.
>If you wish to survive, squelch your opinions, say yes to anything the
>hierarchy has to say, and start talking about yet another popper clone. After
>all, poppers are the most agile, wonderful, amazing, better than Robby the
>robot, unbelievably functional, and only true robot ever conceived by man.
>You don't believe me? Just don't say so out loud.
Hmmm. Posted at 10:47am - didn't finish your morning coffee quite yet, eh Jim?
;->
Yes, the simplicity of BEAM means you can build some pretty elegant/nifty
devices that aren't robots in any sense (ie: solarollers/pummers), but they
are a necessary building block to get to the levels of expertise needed to
build true robots. I make it a point to explain that when I'm giving
demonstrations that such devices are NOT robots, because enthusiastic
beginners interpret being on the road to building a robot the same as
building a robot. That's all we're seeing here.
As for quashing opinions, (opening for another heated debate here) I really
have to disagree. If you're interpreting the lack of resounding support and
adoption of every new idea by (what are referred to by others here) the
BEAM "Old-Guard" as DISAPPROVAL and NOT acceptable behavior, well, that's
plain wrong. I for one am not going to repress any sort development because
I'm not crazy about the idea (remember the master BEAM robot index project?).
Other than what I've mentioned right above, I can't imagine what else you
could be possibly referring to as the source of your grumpiness! ;>
Regards,
Dave
---------------------------------------------------------------
"Um, no - that's H,R,Y,N,K,I,W. No, not K,I,U,U, K,I,_W_. Yes,
that's right. Yes, I know it looks like "HOCKYRINK." Yup, only
2 vowels. Pronounciation? _SMITH_".
http://www.solarbotics.com
13488 Sun, 16 Apr 2000 13:48:44 EDT Re: Monitor Salvage beam@sgiblab.sgi.com BUDSCOTT@aol.com I know a good safety tip for that kinda stuff. DON"T STAND IN PUDDLES OF
WATER!!! If you are incredible carefull, and are completely aware of what
parts hold big charges you won't get knocked on your buttocks!
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13489 Sun, 16 Apr 2000 10:51:18 -0700 RE: Monitor Salvage "'beam@sgiblab.sgi.com'" Wilf Rigter Thanks for the Sumitomo PIR scoop,
Aside from the warnings, there are not many components worth scavenging =
from
monitors but look out for small pots, larger power MOSFETs, voltage
regulators and sometimes a complete open frame "offline" switching =
power
supply. The latter usually has >20V , 12V and/or 5V outputs and is =
generally
not safe for beginners since there are exposed connections/contacts at
120VAC and 300VDC, dangerous to life and limb.
wilf
> -----Original Message-----
> From: Tan [SMTP:ptcngan@pd.jaring.my]
> Sent: Saturday, April 15, 2000 10:43 PM
> To: beam@sgiblab.sgi.com
> Subject: Monitor Salvage
>=20
> Hi,=A0 i got a old monitor that is spoilt and i want to salvage it. =
Yeah, i
> know it's dangerous, but it seems such a waste, so anybody have any =
tips?
> Thanks in advance.
13490 Sun, 16 Apr 2000 13:54:05 EDT Re: You guys disappoint me beam@sgiblab.sgi.com BUDSCOTT@aol.com I think that we need to remember what BEAM is about, learning. So there will
still be people building blinkers and flag wavers, they'll eventually build
REAL robots, but the skill level needs to progress. I don't think your being
too critical though, i try to avoid conflict.
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13491 Sun, 16 Apr 2000 13:57:09 EDT Re: You guys disappoint me beam@sgiblab.sgi.com BUDSCOTT@aol.com In a message dated 4/16/00 12:36:30 PM Central Daylight Time,
richfile@rconnect.com writes:
<< I agree to. Technicaly, even solarrollers are autonomous vehicles, but
when I show off my robots, I never _call_ it a robot. I sometimes keep
my photovore down to "light tracker". My walking robots though, I'm more
comfortable with. I think, techniacly, if it has some form of motion to
perform work or move itself, autonomously controlled by electronics,
then you can _technicaly_ call it a robot, but there are limitations.
The word robot has gained a sort of "understood" meaning, and if it's
too simple, people tend to not view it as a robot, even if it technicaly
falls under the more vague definition. >>
Good point, i think that the real definition of a robot is - any type of
machinery that utilizes control devices to complete a task. That makes
walkers a robot, cause a walkers task is to walk, and that makes photovores a
robot, cause they're task is light seeking. See.
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13492 Sun, 16 Apr 2000 14:00:14 EDT Walker competitions beam@sgiblab.sgi.com BUDSCOTT@aol.com Hey Dave! I wanted to ask you how the rules for the walker competitions are
coming! So, how are they comin?
-Spencer
<http://www.botic.com/users/beamstop>
not a robot scientist
not a college major
not a grad student
not a professor
not a very organized person
just Spencer (isn't that impressive enough?)
13493 Sun, 16 Apr 2000 11:09:47 PDT Re: You guys disappoint me beam@sgiblab.sgi.com "Timothy Flytch" I think you are missing the point of BEAM... BEAM is not the top of the
robotic food chain... It's the BOTTOM!!! The amoeba, plankton, protozoa,
and such (and no I don't think we are on the level of insect yet)... Most
of the robot world starts at the top and works down (and are having
considerable trouble with it)... We are starting at the bottom and working
up... Once you get board with BEAM just expand... Once the simple
understanding and hands on experience is there you can design and build your
OWN dream...
But then some of us just love our little LED fire flies to adorn our garden
path... Never laugh at another mans toys (or dreams)... We all have toys...
If this raises your blood pressure and you feel the need to flame... Please
do it off list .
Timothy...
>From: "sebastiaan van Vliet"
>I am a little disappointed in Beam community. I just cant stand people are
>calling a few blinking LED's a bot. Even a solaroller doesn't seem very
>"bot" to me.
>
>Maybe we should make some rules what is a bot and what not or even make
>categories ranging from blinking LED's to 134562 motor walkers with
>76437tons of electronics and are superior to humans.
>
>I don't want to be a pain in the ass, but just want some quality in the
>community.
>
>I hope you all agree with me and forgive me if I made a fool out of you
>because you just finished your garden blinking LED's
>______________________________________________________
>Get Your Private, Free Email at http://www.hotmail.com
>
______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com
Home