Heating power of a 20 watt infrared bar diode?

[DeeLuxx]

Hi there,

I am currently studying botany at university and for a current project we are studying the toxins and pheromones within different plants etc.

To do this we vaporize plant matter and extract different compounds.

im interested in building my own using an infrared laser bar diode as the heating element - this one is for sale on ebay Oclaro 20w 808nm DCS diode laser bar Prolite | eBay - same as in the picture pretty much

So my question is what would be the ability of a bar diode to heat a 2cm x 2cm sample of plant matter evenly and effectively to around 200 degrees Celsius?

is this even possible with a bar diode? would i have to use lenses?

i understand that i wont need all of 20watts otherwise it will probably set the sample on fire

 

[qumefox]

It would likely do the job, however I don't see much of a way to regulate the temperature, since how hot the materials got would depend on the IR absorption of the materials themselves. And that would be a moving target since it would change with different materials.

 

[laser_freak]

It should be simple enough to solve the equations for 20W of radiative heat transfer. The physics are extremely simple and easy to learn.

 

[qumefox]

I don't think 808nm is a long enough wavelength to be what i'd consider a radiant heat source, and like I said, color and type of material exposed will make a huge difference on performance, since lighter colors will reflect more photons. There's also the problem of regulating the temperature. I don't know of any way to do that that wouldn't involve passive elements between the diode and the material heated.. and if going that route, there would be no point in using a laser diode. It would offer no benefit over normal heating elements.

 

[laser_freak]

I don't think 808nm is a long enough wavelength to be what i'd consider a radiant heat source, and like I said, color and type of material exposed will make a huge difference on performance, since lighter colors will reflect more photons. There's also the problem of regulating the temperature. I don't know of any way to do that that wouldn't involve passive elements between the diode and the material heated.. and if going that route, there would be no point in using a laser diode. It would offer no benefit over normal heating elements.

I would have to dig out my physics textbook, but I do not see any reason why all wavelengths should not be considered radiant sources.

 

[Trevor]

I would have to dig out my physics textbook, but I do not see any reason why all wavelengths should not be considered radiant sources.

But if your radiant source's wavelength does not match up with your target's absorption spectra... ><

-Trevor

 

[rhd]

It would likely do the job, however I don't see much of a way to regulate the temperature, since how hot the materials got would depend on the IR absorption of the materials themselves. And that would be a moving target since it would change with different materials.

Some organic foliage is actually incredibly POOR at absorbing infrared. I know this first hand, because with infrared photography, leaves are often dead white.

 

[DeeLuxx]

Hi thanks for all the usefull replies!

For the porpuse of reulating temperature i was going to use a small temp sensor (thermocouple most likely) that was placed in the middle of the sample and colored the same as the sample to absorb a similar amount of radiation and give a move correct reading.

i was thinking about placing the sample in a small (think matchbox size) mirrored chamber so hopefully the reflected radiation will "recycled" as such.

The sample will mostly be the crushed leaves of the flower (daffodils) so will not be a flat surface but look more like a a sample of cooking basil/rosemary etc.

The reason i want to use laser is because it heats the sample very quickly which gives a far better result than other methods. and infrared diodes are VERY cheap on ebay for the power output

 

[Cyparagon]

Why not use a toaster oven?

More to the point, won't heat likely denature many of the compounds you're trying to study?

 

[rhd]

For the porpuse of reulating temperature i was going to use a small temp sensor (thermocouple most likely) that was placed in the middle of the sample and colored the same as the sample to absorb a similar amount of radiation and give a move correct reading.

Comment 1:
It doesn't matter if it is colored the same, unless you happen to have infrared vision. Two leaves sitting next to each other can absorb radically different amounts of IR, even though their color is identical. Why? Because the colors you see, are wavelengths in the visible spectrum - which (although often correlated) doesn't actually say anything about how much IR an item will absorb.

We often comment that IR burns black items a lot better than white items. Realistically, this is a stupid comment for us to make (even though it is often/usually accurate). Black means that an item isn't reflecting any of the visible spectrum that our eyes can pick up. White means that an item is reflecting most/almost all of the visible spectrum that our eyes can pick up. Neither black nor white tells us anything about whether the infrared is being absorbed or reflected.

An interesting example is to look at this:
http://www.onestop-digital.com/archive/images/hoya-ir.jpg
It looks completely pitch black to your eyes. You can't see through it - it looks like a solid piece of *black*. But if you shine an infrared laser at it, absolutely none of the infrared will be absorbed because this particular coating lets all of the infrared through, and none of the visible spectrum.

So, long story short, matching the colour of two different items based on YOUR VISION, doesn't actually match them in terms of infrared absorption.

The sample will mostly be the crushed leaves of the flower (daffodils) so will not be a flat surface but look more like a a sample of cooking basil/rosemary etc.

The reason i want to use laser is because it heats the sample very quickly which gives a far better result than other methods. and infrared diodes are VERY cheap on ebay for the power output

Comment 2:
I know what you're trying to do now Has anyone else figured it out?
You're looking to heat this to "around 200 degrees" eh? What vaporizes at almost exactly 200 degrees....? Oh right, this:
ChemSpider | 2-[3-methyl-6-(prop-1-en-2-yl)cyclohex-3-en-1-yl]-5-pentylbenzene-1,3-diol | C21H30O2

Brilliant idea...a bunch of "really happy people" fumbling around in a garage with a 20W infrared laser diode bar. Oh my, the future is here, and it's depressing.

 

[qumefox]

Hi thanks for all the usefull replies!

For the porpuse of reulating temperature i was going to use a small temp sensor (thermocouple most likely) that was placed in the middle of the sample and colored the same as the sample to absorb a similar amount of radiation and give a move correct reading.

Won't work very well. even the same color, it's still a different material with different absorption, as well as mass, as your samples, meaning it's reading won't match what temperature the samples are actually at. You have to remember this isn't longwave IR your dealing with. Your heating the material itself by doing it this way, not the whole environment (like in an oven). What your wanting to do *IS* technically possible.. however your going to need to know the 808nm absorption rates for your samples, their precise mass, and do some fairly complex math to calculate how much energy you'd need to input to get said samples up to 200C.

 

[qumefox]

Comment 2:
I know what you're trying to do now Has anyone else figured it out?
You're looking to heat this to "around 200 degrees" eh? What vaporizes at almost exactly 200 degrees....? Oh right, this:
ChemSpider | 2-[3-methyl-6-(prop-1-en-2-yl)cyclohex-3-en-1-yl]-5-pentylbenzene-1,3-diol | C21H30O2

Brilliant idea...a bunch of "really happy people" fumbling around in a garage with a 20W infrared laser diode bar. Oh my, the future is here, and it's depressing.

And what is that in layman terms? I'm not up on my chemistry.. or my.. guessing... inhaled substance abuse references.

 

[rhd]

Cannabidiol - Wikipedia, the free encyclopedia

 

[Trevor]

Cannabidiol - Wikipedia, the free encyclopedia

Uh, interesting. Wondering what DeeLux will say.

-Trevor

 

[Meatball]

I would not use a multi-mode diode bar like that to heat anything at all.

That horrid beam will have multiple "hot spots" within the entire beam. This will not make for even heating.

Just get a 100-150W light bulb, or reptile heating lamp. Those put out plenty of IR and whatnot with very uniform output patterns.

No need for the light to be coherent, just "there" in large quantities.

 

[DeeLuxx]

Comment 2:
I know what you're trying to do now Has anyone else figured it out?
You're looking to heat this to "around 200 degrees" eh? What vaporizes at almost exactly 200 degrees....? Oh right, this:
ChemSpider | 2-[3-methyl-6-(prop-1-en-2-yl)cyclohex-3-en-1-yl]-5-pentylbenzene-1,3-diol | C21H30O2

Brilliant idea...a bunch of "really happy people" fumbling around in a garage with a 20W infrared laser diode bar. Oh my, the future is here, and it's depressing.

HAHAHAHAHAHA knew someone would say this was just waiting for it.

Maybe once uni is over.....

But for the time the compound we are studying at the moment is the toxin in the bulbs (and leaves) of daffodils - Lycorine - ChemSpider | Lycorine | C16H17NO4

it has a flash point of 245 degrees celsius ish so quite similar to the previously mentioned compound.

Interestinly enough though we are actually using a vaprozer designed for the forementioned at the moment - the one pictures below.

It works but doesnt really get quite hot enough and ends up sort of cooking the compount by the time we isolate it so the idea of using a laser is to do it instantly.

I would not use a multi-mode diode bar like that to heat anything at all.

That horrid beam will have multiple "hot spots" within the entire beam. This will not make for even heating.

Just get a 100-150W light bulb, or reptile heating lamp. Those put out plenty of IR and whatnot with very uniform output patterns.

No need for the light to be coherent, just "there" in large quantities.

Our second (and most likely) choice is to use a halogen bulb to heat the sample via radiant heat as they operate at a high temperature and output alot of radiant energy

Im still keen on using a laser though as they heat up the sample alot quicker and give us a better compound to study so does anyone else have any other ideas?