Subject:
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Re: Update on pyroelectric sensor
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Newsgroups:
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lugnet.robotics
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Date:
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Sun, 19 Nov 2000 22:58:27 GMT
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Original-From:
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Henry OneTimeCRX <HCHEA@RAMAPOstopspammers.EDU>
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Viewed:
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Hi,
Sorry, but the web server I used died, and they didn't have any
backups... But I am able to put up my work at another site, though this
one will be temporary:
http://orion.ramapo.edu/~hchea/pyro.htm
A pyroelectric sensor is a differential sensor, meaning that it can only
detect ifrared MOTION. That means that it can't detect an infrared
source, if that source is sitting still. So yes, it is normal that you
only get spikes in sensor readings when a source moves, but no reading
at all if the source is stationary.
When I wrote:
> ...if I stand several feet away, the readings are very steady and accurate.
> It takes about 10 seconds to give a stable sensor reading of 45.
I'm sorry for the confusion; I should have written it better. Those two
sentences are completely unrelated to each other.
What I meant by the first sentence, "if I stand several feet away, the
readings are very steady and accurate.", is that if I stand several feet
away and move around, the sensor tracks my motion very reliably. If I
stand a few centimeters away, and move around, the sensor readings
aren't so good.
What I meant by the second sentence, "It takes about 10 seconds to give
a stable sensor reading of 45.", is that the sensor requires 10 seconds
to warm up when it is first powered, then it hovers at a steady sensor
reading of 45 with no moving object sensed.
The output of my sensor goes as follows:
45: when there is no moving object in front of the sensor. Note that
this could mean that there is an object in front of the sensor, but if
it's not moving, the sensor won't notice it.
0 to 30: an object is moving on the left side of the sensor.
50 to 100: an object is moving on the right side of the sensor.
One way you could detect a stationary object is to move the sensor
around a little bit, that's how my videobot was able to find people even
if they stood still.
BTW Sven, if you don't mind me asking, which pyroelectric sensor are you using?
PS Greg, I haven't forgotten to do a datalog on my pyro sensor; I simply
have to find an IR cradle first!
Hälsningar/
Henry Chea
________________________________________
/ Göteborg, ja ja, jag behöver inget mer!
______________________________
/ Skriv till: OneTimeCRX@aol.com eller hchea@ramapo.edu
> Subject: Re: Update on pyroelectric sensor
> Date: Sun, 19 Nov 2000 02:23:27 +0100
> From: Sven Hartmeier <spindle@gmx.net>
> To: OneTimeCRX@aol.com
> CC: Sven Hartmeier <spindle@gmx.net>
> References: <cf35f15.2511db52@aol.com>
>
> Hej Henry!
>
> On September 16th, 1999, you posted this message to lugnet.robotics:
>
> > For those who are interested, I got my pyroelectric sensor working. I am
> > using a differential amp setup, and it works just fine. Right now it is on • a
> > breadboard, but I will transfer it to pcb soon. • [...]
> > I haven't tried any
> > programming yet, but it looks like the sensor will work well enough to be
> > able to find animals and other IR sources from at least two meters away.
> > Cool. I hope to have the electronics diagram made and up on the web soon.
>
> I've been trying to hook up an pyroelectric sensor to my RCX for a while now,
> but the results have been quite disappointing. I could not get it to react
> like I wanted it to. I would like to have it detect a heat-source and deliver
> a constant voltage signal while the source is visible, and lower readings
> when there is nothing in front of it. So far I could only get a pulse
> signal when the heat source moves into the field of view and another pulse
> when it leaves again, but there is no reading while the heatsource is not
> moving. Therefore I am very interested in your solution to this problem, since
> from your description it seems that you got this solved:
>
> > ...if I stand several feet away, the readings are very steady and accurate.
> > It takes about 10 seconds to give a stable sensor reading of 45.
>
> Could you please tell me if you've already found the time to put your
> resources online, and if you did, provide me with a pointer to their
> position?
>
> Thanks in advance and
> Happy building !
>
> Sven
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