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Cadmium Sulfide Flame Sensor

Is there a way I could tie this in with a simple circuit to activate a
series of relays when it senses flame? I am building a small turret
that will first seek brightness (in a dark room, so for example, a
candle) and then when the flame sensor sensor is facing it, activate a
series of relays, some ceasing motion of the 'turret' and one
triggering a pump which will squirt a spray of water in the direction
of the candle or other type of flame. The distance of the flame from
the sensor is required because I want to be able to move the candle
and still have the turret track a different location.

http://www.grainger.com/Grainger/items/1D294?BaseItem=2E360

If possible, I would also like to have the sensor indicate once the
flame is extinguished, and reactivate the turret. This project is
similar to the firefighting robots competition, only the turret is
stationary.

http://www.trincoll.edu/events/robot/

Any and all help is appreciated!:)
 
E

ehsjr

Jan 1, 1970
0
Bob said:
On the other hand, dual CdS sensors could be used
like that old Carl and Jerry episode from Popular
Electronics back in the '60s to track a moving
flashlight. (Boy, am I showing my age!) The idea
was that the right sensor activated the left wheel
of the robot, and the left sensor activated the
right wheel. If the light was straight ahead, the
robot charged straight at it; otherwise, it turned
until both sensors were equally illuminated.

I always wanted to build one of these, but never
got a round to it... <g>




* *
* *
* TUIT *
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:)
 
On Tue, 10 Mar 2009 20:20:59 -0500, Tim Wescott
[snip]

On the other hand, dual CdS sensors could be used
like that old Carl and Jerry episode from Popular
Electronics back in the '60s to track a moving
flashlight. (Boy, am I showing my age!) The idea
was that the right sensor activated the left wheel
of the robot, and the left sensor activated the
right wheel. If the light was straight ahead, the
robot charged straight at it; otherwise, it turned
until both sensors were equally illuminated.

I always wanted to build one of these, but never
got a round to it... <g>

If you just want to move the turret and not the
whole robot, you'd need some logic to stop the
motors when both sensors were equally lit.

Best regards,


Bob Masta

I remember reading that Carl & Jerry story (among many others) - and
wishing I chad the $ to duplicate it ;-)

I wonder how many others were fascinated with their projects?

John
 
Yes but.

Yes, you can use some sensors like that.

But they may not be sensitive enough to detect a single candle flame in a
dark room (CdS sensors like that are usually used inside of furnaces,
pointed right at a bright yellow flame less than a foot away).

And CdS sensors are slooooooow.

So you would have to amplify their output, you'd have to use at least two
(to sense the direction to the candle), and you'd have to _really_ slow
your application down.

Why not use a camera and some simple microprocessor signal processor,
instead of 1940's sensors driving 1940's electronics?  You can get web
cams these days for a pittance, USB has been around long enough that you
should be able to get an old slow laptop for cheap, and if you don't like
that solution you can get all the bits to build your own camera for
fairly cheap.

--http://www.wescottdesign.com

Oh well...
I had thought that they sensed flame based on heat, not light. I had
previously sonsidered using an IR sensor to detect the flame but was
informed at how difficult it would be to accurately detect flame, and
how expensive it would get. ):
Do you have any alternative suggestions to detect the flame? I had
planned on using light sensors I have salvaged to run two sets of
motors. One controlling X axis movement and the other Y. So basically
all I need is something that can detect a flame fairly close to
directly ahead of it...but a range of more than a foot would be
nice...thanks for all previous and future submissions!
 
S

Sjouke Burry

Jan 1, 1970
0
Oh well...
I had thought that they sensed flame based on heat, not light. I had
previously sonsidered using an IR sensor to detect the flame but was
informed at how difficult it would be to accurately detect flame, and
how expensive it would get. ):
Do you have any alternative suggestions to detect the flame? I had
planned on using light sensors I have salvaged to run two sets of
motors. One controlling X axis movement and the other Y. So basically
all I need is something that can detect a flame fairly close to
directly ahead of it...but a range of more than a foot would be
nice...thanks for all previous and future submissions!
If you have access to OLD broken? cd players, they have interesting
photosensors.
I have found one with ~8 mm (1/3 inch) four quadrant cell, and if you
put a badly focushed picture of the flame on it, and put differential
amplifiers between the horizontal pair and the vertical pair,
you can sense the direction of the flame in two dimensions.

Use a piece if infrared filter from a broken remote control, to stop
visible light.
 
D

Don Klipstein

Jan 1, 1970
0
If you have access to OLD broken? cd players, they have interesting
photosensors.
I have found one with ~8 mm (1/3 inch) four quadrant cell, and if you
put a badly focushed picture of the flame on it, and put differential
amplifiers between the horizontal pair and the vertical pair,
you can sense the direction of the flame in two dimensions.

Use a piece if infrared filter from a broken remote control, to stop
visible light.

A combo of red and green acrylic / "plexiglas" sheets passes most IR
that silicon photosensors sense, and blocks visible rather well.

Keep in mind that a yellow flame has ratio of IR to visible merely an
order of magnitude (or somewhat less) above that of incandescent lighting
and incandescent flashlights. Also consider that sunlight and daylight
have a significant amount of such infrared, especially direct sunlight.

Do not plan on achieving something that reliably hoses candles and
reliably does not hose incandescent flashlights with an engineering effort
short of or possibly even comparable to "college/university
engineering-major senior design project", which is something done by a
group rather than by an individual.

- Don Klipstein ([email protected])
 
D

Don Klipstein

Jan 1, 1970
0
One place to start would be browsing the archives of the
comp.robotics.misc newsgroup. I seem to recall the use of UV sensors
to distinguish "flame" from "light", but I don't remember the exact
details.

There are flame detectors that sense 310 nanometer UV, which is a UVB
wavelength close to borderline UVA, that blue flames produce weakly.
Small flames usually have a blue region producing some of this wavelength.

Keep in mind that this wavelength is only weakly produced by flames, and
flame sensors based on this wavelength assume lack of this wavelength from
normal light sources. However, many fluorescent lamps can produce enough
of this wavelength (even when not to an extent problematic to humans) to
confuse flame sensors based on this wavelength. A few incandescents,
especially some halogens, can do likewise. Daylight also usually has
enough of this wavelength to trigger flame sensors based on this
wavelength.
There are common filters to block this wavelength from "legitimate light
sources" to allow such light sources to be used where flame sensors using
this wavelength are used, including most polycarbonate plastic sheet
materials such as "lexan".

There are also flame sensors based on a very deep UV wavelength of
hydrogen, 121.6 nm - which is a "vacuum UV" wavelength that does not get
through air well (nor most other tyranmsparent materials). It works as a
detector of flames, preferably blue flame such as flame bases, only in
very close proximity. This wavelength is only very weakly emitted by blue
flames, and flame detectors based on this wavelength assume lack of such
wavelength from other sources. Sensors for this wavelength may also
detect radioactivity and X-rays.
If you'd like a rapid-acting non-contact thermal (IR) sensor,

Please keep in mind that many, probably most yellow flames are far
short of "full thermal radiators".

I just tried my "Raytek" non-contact thermometer on a 6 inch diameter
pan with a shallow layer of 91% isopropyl alcohol ignited by a He-Ne laser
power supply. The fire was merely somewhat small and just a little on
the dim side for a fireplace, and the flames had temperature readings
almost entirely less than 150 degrees C, mostly less than 90 degrees C.
check out the Melexis MLX90614 from:

Melexis Microelectronic Systems
http://www.melexis.com/

If you think that the MLX90614 would be useful, you can purchase a
serial-interface module from Parallax:

Parallax http://www.parallax.com/

- Don Klipstein ([email protected])
 
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