My guess is yes, if they are moving. Since they emit infrared, that's a check. The PIR actually doesn't care what's in the room, rather, it only cares if the infrared signature changes quickly (maybe ~cm/sec). So, it should work as a primative fire sensor. However, it probably wouldn't notice anything until it got to be rather large. But, if you are making a romatic table setup with candle light in the same room that you have your homemade thief system, then you should be safe.
If you’re trying to track a candle you won’t be able to do that. The PIR only senses a dramatic change in the IR in its field of view. If the PIR were sitting still for a minute and a candle was suddenly introduced, it should be able to detect that though. It sounds as though what you really need is a thermopile. We have such a unit at the link below. I hope this helps. Take care.
Thanks for the info. And just to let you guys know, the reason why i asked is because im trying to make a firefighting robot and i thought that the pir sensor would be able to detect the flame. If anyone has any ideas please post them on this forum.
The MLX90614 Infrared Module is a great little unit and, for $26.99, a bargain! But, from the specs, and from my experience, it will not detect incandescent subjects, such as flames. The reason is that these are well beyond the temperature range it was designed to sense (-70 to 380 degrees Celsius). Nonetheless, it has some amazing capabilities, and makes a fine addition to anyone's sensor arsenal.
You might try three infrared photransistors, either separated by opaque baffles or aimed at 30º increments (the middle one looking straight ahead. Their relative outputs will give you the direction of the flame, and their aggregate output will hint at its proximity.
I don't think that sensor will work either. It's designed for body-heat motion sensing apps and, like the MLX sensor, is insensitive to wavelengths shorter than about 6 microns. For flame detection, you need something that can sense near-IR (1 to 2 microns). To understand the difference, consider that if the candle were being used to boil a cup of water, these pyroelectric sensors would see the hot cup, but not the naked flame.
From the description: "Since the UV energy emitted by a flame bounces off walls, you don't even need to have a line of sight to the flame to detect it in a room." If you're trying to locate the flame, not just detect that one is there, this may not be the best solution. For flame location, I'd try IR phototransistors, before I spent $80 on a UV flame detector. Here is an article that might help you make up your mind.
Some clerification on lightwave spectrum. Thermal IR is in the range of 3 to 14 microns. Thermal IR is heat, such as that given off by flame, body heat or any hot object. This is known as far-IR. The definition of far-IR is very merky however. Some consider far-IR as being from 14 to 1000 microns. Reflective or photo IR is in the range of 0.7 to 3 microns. Technically photo IR is a subset of reflective IR, in the range of 0.7 to 1.3 microns. This is near-IR. Again there is a merky definition of near-IR. Some consider near-IR as being from 0.75 to 15 microns. The PIR sensor mentioned, is specifically designed to detect human body heat in the range of 9 to 9.4 microns. That PIR sensor will detect flame, but is not a good choice for flame detection because of the narrow bandwidth of 9 to 9.4 microns. Other PIR sensors with a wider bandwidth do work fairly well detecting flame, but thermocouples do a much better job of flame detection. PIR sensors only detect changes in heat/temperature. The only way the PIR detect flame is if the flame is moving or flickering, causing temperature changes. Hope this will clerify.
thanks LIlDi and everyone else who is helping me out. Can someone please tell me how the sensors work on the boe bot that was able to follow the flame.
Andy has pretty much given an excellent explanation on how the sensors work (Flame Seeking Boe-Bot Robot) in the link that I 'dug' up. Please review the information, links, and examples he has provided. If possible you might want to re-create his efforts to see if this might be practical for your application. It is up to you to do the necessary research to achieve your goal. If you still have questions please feel free to ask, specific questions, about what part you need help with.
This response is not to 'spank you' but to encourage you to 'ferret out' answers to your own questions.
And by all means, if you have a success, please post your project in the 'Completed Projects” section of the forum. This will enable all of us, and future users,·to benefit and learn from your expertise!
Alright, I did what you said and the only question that i have now is were are the recievers. I see IR LEDs but no recievers. theres also aren't any schematics for recievers.
Look on page 10 for: ACTIVITY #2: DETECTING LIGHT LEVEL WITH AN LED, this is where Andy (I'm assuming he wrote this document) describes how an LED can be used as a detector.
I think you need to be real careful in choosing an IR sensor. That photo transistor in the firefighting write up is a UV sensor, not a thermal IR sensor. I'm not sure how much UV a flame produces. Probably not very much. Those photo sensitive LEDs are sensing the visible light of the flame, not thermal IR. The photo diode in the sun tracker is just following the visible light of the sun as well. Most plastics and glass strongly attenuate thermal-IR light. A piece of glass in front of a PIR will render it useless. My vote is for that dirt cheap MLX90614 non contact temperature module. At least its actually sensing thermal-IR.
LilDi said...
That photo transistor in the firefighting write up is a UV sensor, not a thermal IR sensor.
Actually, in the write-up I posted a link to, the phototransistor is for IR. Quoting from the document, "...it was determined one set of devices performed better than all the rest in our IR-noisy environment (energy-saving electronic ballast flourescent lighting). These were unmarked Honeywell IR phototransistors in a tiny black rectangular package. The Electronic Goldmine part # for these is G9412."
-Phil
Addendum:Here (on the third page) is the Electronic Goldmine 2001 catalog section containing those prototransistors (#G9412). Unfortunately — but not unexpectedly — they are no longer in stock. But a call to their purchasing department may be all it takes to get the Honeywell part number.
Post Edited (Phil Pilgrim (PhiPi)) : 10/30/2008 4:35:15 AM GMT
While this is a fascinating subject, the Ottowa Robotics site Phil called out is more useful. It points out that a candle flame DOES put out UV light, and heat, and IR, and details a few sensors specifically for candle-flame detection.
It sounds like very few of us on this forum have actually created a candle-flame sensor, so our answers go all over the map -- IR, IR-LED, IR-Transistor, UV, UV-Sensor, Heat sensors, etc. Also, each of these sensors can be up to $25 or $50 -- so you can spend a bit of money coming up with a good 'sensor suite'.
BOB55,
That OP520 sensor will not respond to thermal-IR. Its IR sensing range is in the photographic-IR range of 880nm. Thermal-IR is in the range of 3000nm to 14000nm. Again this is not a heat sensor.
For detecting and locating flames, you don't want a thermal sensor, as I explained in several posts prior. The reason is that the wavelengths emitted by a flame are typically too short to be detected by one. At least this has been my experience with the Melexis sensor, whose lower wavelength range extends to 5.5 microns. I could light a match and hold it in front of it, and the reading would be unaffected. This was done for a reason: to make the unit insensitive to sunlight, which is also an "incandescent" source.
Flames do emit a lot of near IR however. Andy Lindsay's post, referenced on the first page of this thread, is an excellent and very inexpensive method for flame detection. If I were doing this project, that's where I would start.
-Phil
Post Edited (Phil Pilgrim (PhiPi)) : 10/31/2008 4:22:01 PM GMT
Comments
http://www.parallax.com/Store/Sensors/TemperatureHumidity/tabid/174/CategoryID/49/List/0/Level/a/ProductID/520/Default.aspx?SortField=ProductName%2cProductName
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Engineering
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Engineering
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
BOB55
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Engineering
You'll probably want one of the extension cables, though, to give yourself some mounting flexibility.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
BOB55
-Phil
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Just a few PropSTICK Kit bare PCBs left!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
BOB55
-Phil
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
'Just a few PropSTICK Kit bare PCBs left!
But the parallax sensor should work just as well and is cheaper. Just make a cone like the one shown and pan it.
The key with either sensor is that it has to be moving or they won't detect. They measure change in heat, not heat.
Post Edited (Larry) : 10/29/2008 5:32:35 AM GMT
-Phil
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
BOB55
-Phil
http://forums.parallax.com/showthread.php?p=703572
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Mike
The word "Here" in my post is the link.
Mike,
Excellent recall! That's a great ref for this topic!
-Phil
Post Edited (LilDi) : 10/29/2008 9:20:13 PM GMT
http://forums.parallax.com/forums/default.aspx?f=6&m=245037
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
BOB55
Andy has pretty much given an excellent explanation on how the sensors work (Flame Seeking Boe-Bot Robot) in the link that I 'dug' up. Please review the information, links, and examples he has provided. If possible you might want to re-create his efforts to see if this might be practical for your application. It is up to you to do the necessary research to achieve your goal. If you still have questions please feel free to ask, specific questions, about what part you need help with.
This response is not to 'spank you' but to encourage you to 'ferret out' answers to your own questions.
And by all means, if you have a success, please post your project in the 'Completed Projects” section of the forum. This will enable all of us, and future users,·to benefit and learn from your expertise!
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Mike
Post Edited (Mike Cook) : 10/29/2008 11:05:08 PM GMT
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
BOB55
Andy is using the IR LEDs as receivers, see the following schematic, (farmed from the original link that I posted):
http://forums.parallax.com/attachment.php?attachmentid=51627
This might explain what's going on here, sorry another link that I 'dug' up:
ftp://ftp.parallax.com/EDU/Old/Tracker/PDF%20Docs/Solar%20Tracker%20with%20the%20BASIC%20Stamp%20_Draft%20029_.pdf
Look on page 10 for: ACTIVITY #2: DETECTING LIGHT LEVEL WITH AN LED, this is where Andy (I'm assuming he wrote this document) describes how an LED can be used as a detector.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Mike
Flame on
Post Edited (LilDi) : 10/30/2008 3:15:57 AM GMT
-Phil
Addendum: Here (on the third page) is the Electronic Goldmine 2001 catalog section containing those prototransistors (#G9412). Unfortunately — but not unexpectedly — they are no longer in stock. But a call to their purchasing department may be all it takes to get the Honeywell part number.
Post Edited (Phil Pilgrim (PhiPi)) : 10/30/2008 4:35:15 AM GMT
It sounds like very few of us on this forum have actually created a candle-flame sensor, so our answers go all over the map -- IR, IR-LED, IR-Transistor, UV, UV-Sensor, Heat sensors, etc. Also, each of these sensors can be up to $25 or $50 -- so you can spend a bit of money coming up with a good 'sensor suite'.
http://www.photonics.com/content/spectra/2006/January/products/77111.aspx
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
BOB55
That OP520 sensor will not respond to thermal-IR. Its IR sensing range is in the photographic-IR range of 880nm. Thermal-IR is in the range of 3000nm to 14000nm. Again this is not a heat sensor.
Post Edited (LilDi) : 10/31/2008 3:44:55 PM GMT
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Chris Savage
Parallax Engineering
For detecting and locating flames, you don't want a thermal sensor, as I explained in several posts prior. The reason is that the wavelengths emitted by a flame are typically too short to be detected by one. At least this has been my experience with the Melexis sensor, whose lower wavelength range extends to 5.5 microns. I could light a match and hold it in front of it, and the reading would be unaffected. This was done for a reason: to make the unit insensitive to sunlight, which is also an "incandescent" source.
Flames do emit a lot of near IR however. Andy Lindsay's post, referenced on the first page of this thread, is an excellent and very inexpensive method for flame detection. If I were doing this project, that's where I would start.
-Phil
Post Edited (Phil Pilgrim (PhiPi)) : 10/31/2008 4:22:01 PM GMT