J
jasen
- Jan 1, 1970
- 0
I would like to see the flame involved. Just to satisfy my lack of
understanding.
http://en.wikipedia.org/wiki/Gas_absorption_refrigerator
Bye.
Jasen
I would like to see the flame involved. Just to satisfy my lack of
understanding.
That is actually a thermocouple. The 'tube' is miniature MICS cable.
DON'T even TRY to get an output from it. That WOULD be dangerous, like
BANG!, or wake up dead.
No, they used to have yellow flames, those running from town gas. I
didn't take into account that this fridge runs from bottled gas; these
fridges have a BLUE flame, not a COLOURLESS one which some posters
thought. The visible light is easily detected with a phototransistor.
Electronics isn't really my field so this is an appeal for help for
something which is probably embarrassingly easy if you know what you are
doing.
I want to detect the presence or absence of a small gas flame (caravan
fridge) and light an led if the flame is there and turn it off if the
flame isn't there. A reasonably quick response time is needed.
Presumably a thermocouple (I think I have read the term "K type"
somewhere), a transistor an led and a resistor or two will be involved!
It would be nice if I could run it off 12v DC and it would be nice if
the current drain could be zero or at least tiny if the led is off.
Any thoughts welcome.
TIA
Peter
I know the problem, I toured much of Europe 30 years ago with a hired
campervan. The bloody fridge had the "flame viewing" window about 1
inch above the floor with a viewing angle of perhaps 15 degrees. The
only way to view it was with a mirror and the lights out.
There's a number of systems in place, I had a heatpump with gas
booster that used a TC sensor. It never failed in the 5 years I was
living there. Or they use a gas-filled capillary tube that shuts off
the gas with no flame.
More modern systems use an optical system, as other have suggested,
and it's possibly the easiest to home-build. The best detectors are
possibly the Hamamtsu ones. See:
http://jp.hamamatsu.com/products/node.do?dir=/division/etd/pd001/pd006&lang=en&ext=html
Glen said:From the instruction label inside my Dometic gas fridge:
IMPORTANT ... 2. Inspect the flame for colour, it should be blue
throughout - no yellow or other discoloration. ...
A yellow smokey flame is a very bad idea because the soot will foul
the heat exchanger. I expect you have seen a fridge with the burner
air holes blocked, or a fridge designed by someone completely
clueless; I have seen quite a few gas fridges and none were designed
to operate with a yellow flame.
If you don't think the OP should mess with the burner, how about a
thermistor an inch or so above the top of the stack, where it cannot
possibly interfere with flue gas flow? Or possibly a temperature
switch, if the flue gas temperature is always well above maximum
expected ambient?
My Dometic has a light pipe with a prism on the end for flame
observation, which works well and can be seen while standing up
although the door must be opened as it is located inside next to the
thermostat. The far end of the light pipe, which is basically a piece
of 1/4" or so acrylic rod, is well back from the flame so as not to
interfere with it.
Those blue flames emit quite an amount of UV (hydrogen line). Don't
know if there are any cheap and easy-to-get sensors for that. I have a
sensor from the sixties I grabbed off a furnace controller. Gas-filled
bulb with two electrodes, runs at 150V, operates like a geiger tube.
Doesn't sense sunlight but makes quite a storm in the speaker if you
flick your bic close to it.
- YD.
dated Mon said:I believe there is a high degree of UV in this flame and it is possible
that one of the InfraTec sensors with a UV filter might do the job.
Ross Herbert said:for LPG is blue with no yellow tip. I believe there is a high degree
of UV in this flame and it is possible that one of the InfraTec
sensors with a UV filter might do the job. Somehow, I think they might
be expensive.
But if you can SEE it, it must emit VISIBLE light. Why bother with UV?
For extra light, put a tiny piece of chalk in the flame. Limelight!
But if you can SEE it, it must emit VISIBLE light. Why bother with UV?
For extra light, put a tiny piece of chalk in the flame. Limelight!
Ken Smith said:If it is U enough V, perhaps just looking for a leakage current from a bit
of zinc plated metal would be enough. Sunlight will discharge an
electrometer with a zinc plate attached.
Charged which way? Quite a feat if the UV is kicking out positrons. ;-)
Checking a table I see zinc has a work function that isn't particularly
impressive;
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/photoelec.html#c1
magnesium would be more suitable, at least as bare metal.
However, zinc
oxide (present on the surface of zinc metal) is a known semiconductor (band
gap 3.2eV, which would respond to UV and blue).
But if you can SEE it, it must emit VISIBLE light. Why bother with UV?
dated Tue said:Because LPG flame, according to the physicists, is in the UV range. It
may be visible under certain circumstances or if other impurities
exist. If it is pure LPG flame then I wouldn't want to gamble on it
being visible under all circumstances.
So the little window provided by the fridge makers so you can see the
flame is not only inconveniently-sited but fundamentally useless anyway.
I rather doubt it.
dated Tue said:It may be that manufacturers of gas refrigerators have worked out that
after settling in the flame will start to become "sooty" and therefore
visible.
My understanding is that only a small amount of heat is required and a
'with air' (Bunsen) flame is too hot as well. So the flame is more like
a candle flame. Certainly, the flame in the fridge in my friend's
caravan was quite visible if you didn't try in bright daylight with
nothing to create a shadow,
Because LPG flame, according to the physicists, is in the UV range. It
may be visible under certain circumstances or if other impurities
exist. If it is pure LPG flame then I wouldn't want to gamble on it
being visible under all circumstances.
http://www.sbf1.sbfisica.org.br/procs/2006/pdfs optics/
Spectroscopy%20and%20Confinement%20of%20Atoms/
892.pdf#search=%22lpg%20flame%20spectrum%22
LPG flame spectra was measured between 415 - 440nM which puts it in
the UV range so it is either totally or near invisible.
In the gas detection and flame detection industry (eg. LPG/LNG storage)
General Monitors FL3101 is a UV only flame detector but it is recommended
for LNG/LPG flame detection according to the spec sheet
http://www.generalmonitors.com/downloads/literature/flame/
FL3100_FL3101_DATA.PDF