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Author Topic: fire detection with uv sensor  (Read 2249 times)
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picavr
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« on: March 06, 2009, 06:48:55 18:48 »

i need for an personal project,any schema or circuit and application about a detection of fire with uv (ionisation) sensor system
thanks ...
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oldvan
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« Reply #1 on: March 20, 2009, 07:05:33 19:05 »

I recall reading years ago that a neon bulb biased to slightly below its firing voltage makes a good flame sensor.

I vaguely recall trying it and sure enough it woud be dark until I struck a lighter near it, then it would light.

For cheap, can't beat a NE-2.  Power supply could be a switchmode converter, I've seen schematics for such
on the 'Net for use in Nixie Clocks.
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pushycat
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« Reply #2 on: November 12, 2010, 10:21:18 10:21 »

Any schematics or links for the same?..when googled, I found a project kit on the web which was using the same principle using a neon bulb and some other components but no details or schematics were available.
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oldvan
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« Reply #3 on: November 12, 2010, 05:34:54 17:34 »

What voltage do you plan to power your project from?
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pushycat
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« Reply #4 on: November 13, 2010, 08:32:45 08:32 »

I would prefer 12 volts to be on the safer side. When neon needs a higher voltage to conduct, i would welcome any application reference even with other voltages.
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oldvan
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« Reply #5 on: November 13, 2010, 04:29:20 16:29 »

A MAX1771 is a convenient way to convert 12VDC to the voltage you will need
to supply the neon bulb.

http://www.maxim-ic.com/datasheet/index.mvp/id/1030/t/al

The concept is amazingly simple, a neon bulb fires at a lower voltage with IR
present than it does in darkness.

Bias the neon bulb to a voltage just below its firing point without IR present,
then apply IR such as from a flame, the neon fires.  Detect the change in
voltage across the bulb's terminals, you have a simple flame detector.
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engamor
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« Reply #6 on: November 13, 2010, 08:38:10 20:38 »

This is NOT a subject that I know deeply. Therefore this is my curiosity. I remember that ionisation chambers are used for smoke detectors. While you started speaking of ionisation chambers and now are speaking of flame detectors, with a neon bulb. Possibly my confusion uh?
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pushycat
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« Reply #7 on: November 14, 2010, 03:28:56 15:28 »

Making a neon bulb below its firing point i had thought about how to do it. I was wondering ..when the neon is connected to the voltage generator, how to connect it to any sensing section. Your words "Monitor the voltage across the neon" enlightened me. Thanks a lot for guidance.
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oldvan
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« Reply #8 on: November 14, 2010, 08:01:13 20:01 »

While you started speaking of ionisation chambers and now are speaking of flame detectors,
with a neon bulb. Possibly my confusion uh?

Usually I'm the confused one, but it appears that this is definitely your confusion.  Post topic
says "fire detection with uv sensor", and the only mention of ionization other than yours was
that Picavr mentioned it in his original post,  "detection of fire with uv (ionisation) sensor
system."

Oh well, the neon gas is ionized when the bulb fires, so there is some overlap of thoughts.

If I had to pick, I'd rather there be many million neon bulbs in the landfills than many million
ionization smoke alarms each containing 3 ug of americium-241.
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