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Infrared detectors

M

mkr5000

Jan 1, 1970
0
How can these vary as far as "angle of detection"? Can they be very directional and some parts be very broad (180 degrees even?) or does it all depend on the type of lens you might use?

I want to build a simple wireless heat detector for a stove and may not be able to point it "directly" at the stove. (I can get close though).


Thanks.
 
C

Charlie E.

Jan 1, 1970
0
How can these vary as far as "angle of detection"? Can they be very directional and some parts be very broad (180 degrees even?) or does it all depend on the type of lens you might use?

I want to build a simple wireless heat detector for a stove and may not be able to point it "directly" at the stove. (I can get close though).


Thanks.
You will need to look at the datasheets for each individual part.
Their angle of view can vary wildly depending on the materials and
construction. Any 'optics' such as lense or sheilds will also have an
effect. Remember, the wider the field of view, the less 'signal' from
our stove you are going to received, so you want it wide enough to get
your target, but not any wider!
 
M

mkr5000

Jan 1, 1970
0
Wonder if I can use one of these cheap PIR motion modules and adjust the sensitivity so it's NOT very sensitive?

I'm trying to detect heat from a wood stove about 3 feet away and using something that senses ambient room air temperature won't cut it -- need something that reacts the minute the stove is burning well -- thought maybe IR could do it?

And no, don't want to mount a thermal switch ON the stove.
 
Wonder if I can use one of these cheap PIR motion modules and adjust the sensitivity so it's NOT very sensitive?

I'm trying to detect heat from a wood stove about 3 feet away and using something that senses ambient room air temperature won't cut it -- need something that reacts the minute the stove is burning well -- thought maybe IR could do it?

And no, don't want to mount a thermal switch ON the stove.

something like this? https://www.sparkfun.com/products/9570

comes in different versions with different field of view, from the
comments it looks
like it is the 10degree version

-Lasse
 
M

mkr5000

Jan 1, 1970
0
I saw that on sparkfun just this morning. Actually, don't need it to react "immediately" after a fire just when the stove starts radiating good heat from the surface (usually 1/2hr to an hour. And when it cools down, opens the circuit.

Want it wireless because I'm a neatnic -- don't want a wire dangling from my stove and have a nice 120v outlet on the floor right beneath it (hence, bud box and a sensor right there on the outlet).

It would also be hidden pretty much from movement of people in the room.
 
J

Jasen Betts

Jan 1, 1970
0
Wonder if I can use one of these cheap PIR motion modules and adjust
the sensitivity so it's NOT very sensitive?

they detect rapid temperature changes. probably unsuitable.
I'm trying to detect heat from a wood stove about 3 feet away and
using something that senses ambient room air temperature won't cut it
-- need something that reacts the minute the stove is burning well --
thought maybe IR could do it?

maybe a black thermistor and a headlight reflector to focus the heat?

hoe long does it take the stove ti get hot after it's burning well
enough?
And no, don't want to mount a thermal switch ON the stove.

can you put a sensor on (or in) the flue?
 
D

DecadentLinuxUserNumeroUno

Jan 1, 1970
0
they detect rapid temperature changes. probably unsuitable.


maybe a black thermistor and a headlight reflector to focus the heat?

hoe long does it take the stove ti get hot after it's burning well
enough?


can you put a sensor on (or in) the flue?


Harbor freight, $20 infra red thermometer. laser pointed.

Fresnel lens, quite accurate. Best 'thermometer' value in my entire
collection. I have more accurate contact type transducers, but this one
does the job, and I carried it in my pocket for a coupe years too.
Still works fine.
 
M

mkr5000

Jan 1, 1970
0
maybe I'll get one and take the guts out. never owned one of those and wonder how "directional" an IR sensor can be? I mean, I understand the laser being able to point but an IR detector? I suppose you just make sure there are no other IR sources close to it (how close?)

Sure, if you point it toward a ceiling vent with nothing nearby but?
 
M

miso

Jan 1, 1970
0
Well yes, but he probably meant the sensor in the PIR motion detector.
They use a thin film type sensor. The sensor is also microphonic.
 
M

mike

Jan 1, 1970
0
maybe I'll get one and take the guts out. never owned one of those and wonder how "directional" an IR sensor can be? I mean, I understand the laser being able to point but an IR detector? I suppose you just make sure there are no other IR sources close to it (how close?)

Sure, if you point it toward a ceiling vent with nothing nearby but?
There are a zillion cheap wired or wireless motion-activated devices.
Pick one that has the output you want.
Remove the fresnel lens.
Stick it behind a small computer fan to act as a shutter.
May have to cut some of the blades off. Run the fan as slow
as practical.
Stick a pipe on the front end to restrict the field of view.
Point it at the stove.
Depending on the filtering in the device, the fan speed
may make a simple sensitivity adjustment. Or maybe
adjust the size of the hole in the end of the pipe.
 
M

mkr5000

Jan 1, 1970
0
When I was a kid, I put a transistor at the focus of a flashlight reflector and

sensed the heat of my hand from several feet away.

what a great idea -- that's what I'll do -- fun project to play with, will have to come up with a cool reflector. small metal funnel maybe?
 
M

mkr5000

Jan 1, 1970
0
just bought a couple. been getting a lot of stuff from china and that's another post I've been meaning to do.

how in the world they provide some of those complete modules at such a cost is beyond me. (and using parts from TI, etc). many of these I've computed parts cost alone (even in qty) -- and it's impossible there would be a profit. ?
 
J

John S

Jan 1, 1970
0
TIL100, used in IR remotes... marvelously sensitive... I've used it
successfully to detect "speed monitored by aircraft" in SoCal... the
props chops the sunlight ;-)

...Jim Thompson

Where can they be purchased, Jim?
 
J

John Miles, KE5FX

Jan 1, 1970
0
Once I got back to GenRad I did some experimenting and found that the
prop chop was a very narrow range of frequencies, so I made a little
magnet mount that I used anytime I was in Californica...
I love to cook with wine.     Sometimes I even put it in the food.

I'm unclear on how that works -- what if the plane never crosses in
front of the sun?

Re: stove heat detection, I've seen people mount old Ge transistors at
the focus of a flashlight reflector. It might make a pretty sensitive
detector if you created a diffamp with one in the reflector and the
other behind it, facing the other direction. Not tried personally...

-- john
 
B

Bill Sloman

Jan 1, 1970
0
I'm unclear on how that works -- what if the plane never crosses in
front of the sun?

The propellors are curved, reflective and twisted. You will probably
get flashes of reflected sunlight modulated at the a frequency that is
the number of blades multiplied by the rotation frequency, though
Jim's scheme might not work on a heavily overcast day. Then again, it
might be difficult to persuade the cop plane to take off into heavy
overcast.
 
M

miso

Jan 1, 1970
0
The cheap way: http://www.ebay.com/itm/221059803110
Ah, the cigarette lighter doubles as a make-up mirror for the ladies.
Well, I suppose with some caution, but it isn't exactly a mirror. Oh,
and I tend to build my camp fires when the sun isn't shining.

But this does seem like a good product to cut your smoking in half.
 
M

miso

Jan 1, 1970
0
The deal with thermal sensing is your hot object is emitting black body
radiation, which has long spectrum (spectral?) tails. That is why you
can view a soldering iron in with some CCD black and white cameras, even
though the CCD is blind beyond a micron.

Color cameras have filters over the CCD elements, and they reduce the
detected IR.
 
M

miso

Jan 1, 1970
0
Turboprops maintain a steady RPM and vary their prop blade pitch to
adjust thrust, so I could see a turboprop having a distinct frequency.
Less so for regular piston aircraft.

Prior to LED lighting being used outdoors, I think it would be safe to
assume any flickering light faster than a few hundred Hz would be prop
reflection. Nowadays it may be more complicated. Even street lights
these days are LED based.

Most LEDs are flashed, though the arguments seem endless if DC or
flashed LEDs are better. Supposedly the eye detects the peak intensity,
so you can PWM the LED for better effective illumination. But I have
seen arguments that DC is better.
 
G

George Herold

Jan 1, 1970
0
The deal with thermal sensing is your hot object is emitting black body
radiation, which has long spectrum (spectral?) tails. That is why you
can view a soldering iron in with some CCD black and white cameras, even
though the CCD is blind beyond a micron.

Color cameras have filters over the CCD elements, and they reduce the
detected IR.

Hey, fun... Re soldering iron. I've got a little ccd I use to image a
~800nm laser. (So no IR filter.) And a weller soldering iron with
the temperature 'programmed' tips. The CCD can't see the 700 F tip.
But the 800 F tip stands out clearly. (And my big 200W Weller
soldering gun is like a torch!)

George H.
 
J

Jasen Betts

Jan 1, 1970
0
Most LEDs are flashed, though the arguments seem endless if DC or
flashed LEDs are better. Supposedly the eye detects the peak intensity,
so you can PWM the LED for better effective illumination. But I have
seen arguments that DC is better.

the brain detects peak intensity, the eye average intensity, if it's
flashing too fast to see you don't see the peak intensity.
 
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