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Cutaway Diagram of Pringles Can Spectroscope using DVD Monochromator for high dispersion.

Cutaway Diagram of Pringles Can Spectroscope using DVD Monochromator for high dispersion.

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The pink-red part is the tinplate metal bum of the can. A slot is cut in it with a drill followed by a Rat-Tail file. The lacquer is scraped off the tinplate with a scalpel blade or Emery Paper so solder will wet the surface, this also serves to clear burrs from the edge of the hole.
A razor blade is snapped in two and the two sharp edges are turned inward to face each other...this will become the fixed slit. One half of the razor blade is lain down on the slotted end of the upturned Pringles can. the sharp edge is positioned to run down the centre of the slot and it is soldered in place by two corners. Double-sided tape could be used to fasten it, but later tweaking adjustments will be more difficult as a consequence. The other half is then lain on the upturned can end and organized to face its sharp edge to the sharp edge of the other half already in place. Something thin and tough, like a piece of shirt box plastic or a feeler gauge could be placed into the forming slit to ensure its width is constant and the two blade edges are parallel. Or the forming slit could simply be sighted by eye. When a good arrangement is achieved, the second half is carefully held down...masking tape is good at this stage....then one corner is tack-soldered to the bum of the can. With just one corner tacked it is possible to move it by small amounts and tweak the slit...once a parallel, narrow slit is obtained the other corner is then soldered down and then the tacked corner is re-soldered, a number of attempts my need to be made to get the desired result...it it all goes "pear shaped" it can always be taken back apart and restarted afresh.

One should procure a number of Pringles cans as one might desire a number if different slits set at different widths and the construction may end up requiring to be longer than a single Pringles Can.

About half to two thirds of the way up the can, cut a slot in the side that extends half way around the can. Make sure the line between the two ends of this cut is parallel to the slit. Get some breakfast cereal cardboard, (Green) and cut a strip from it that is as wide as the diameter of the Pringles Can. Make one end of the strip semi-circular with the same radius as the Pringles Can. Cut a "letterbox slot" in the cardboard strip about 1/8"/3mm wide and in the same position in the cross section as the slit is in the end. A number of tries may be required before the slot is in just the right place. Insert this strip in through the cut made halfway up the can, the "furry" edge of the cut, if made with a tool like a bread knife, should hold the strip by friction, if not "BluTack" or some similar substance could be used to steady it in place....this makes a baffle to block off axis ribbons of light, (orange ray) from the slit that come from unwanted sources angularly near the source whose spectrum is desired, (pale yellow ray). This baffle can initially be omitted if desired to simplify things...but really, there ain't much in this thing anyway.

Blackening all inside surfaces of the can with paint, felt-tip marker or black paper helps immensely,

Various Optical media disks can be used as monochromators or even a purchased reflection or transmission gratings.

CD's, those with the least data density possess the least number of tracks crossing a radius so they act as gratings with fewer number of grooves for unit width and as a consiquence posses the least dispersion. Second and third blazings are generally far enough away not to cause issues and the dispersion is low enough to get the whole visible spectrum into a camera lens.

DVD's, with their higher data density and number of tracks crossing the radius give greater dispersion and higher blazings are closer and more difficult to avoid. With this set up the dispersion is such that not all the spectrum can be accommodated by a single camera position and DVD's generally contain dye layers that absorb large chunks of the desired spectrum. I would assume Blu-Ray disks are similar and probably have a blue dye layer...they can be delaminated, but it is a tricky process that requires sharp blades and loads of patience...if you go this route, be prepared to have more than a few failed attempts before a significant piece of reflection grating is recovered.

CD's have multiple layers which can decrease the resolution of the spectrum due to internal reflections between the layers, so for the highest resolution results the CD may need to be delaminated too.

The final part is holding the camera or sensor steady over the blazing of interest...here you will have to innovate for yourself depending on the type size and shape of sensor you have or choose to use. At some point you will be on your own as I cannot describe every little step in infinitesimal detail...common sense and a few failures should get you to a fully functioning unit within a few days spent with a few hours each day on achieving the set goal of getting your first high res spectrum!

Blazings C.JPG Low Dispersion C.JPG High Dispersion C.JPG Heat Cured Cement Composite.jpg

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Date added:Feb 16, 2019
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xmaslightguy
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^homebuilt fixture


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Aug 06, 2019 at 09:34 PM Author: xmaslightguy
How much distance(inches or cm) should there be between the end with slot & the DVD?
Should the 'card' be precisely centered between the end & DVD?
It looks like the slit is more towards the bottom side...how much distance should it be up from the bottom?

Colored Fluorescent's such as F40T12 Red or  Green or Blue are awesome...

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Aug 06, 2019 at 10:08 PM Author: Globe Collector
There are no real precise quantitative answers to these questions. Generally I use the "suck it and see" method.

The "blade" of light produced by the slit has to impinge in the CD/DVD.

If the source under examination is a fair way away...like a streetlight 50 yards away, then the "blade" of light produced by the slit is nearly perfect and the CD/DVD can be practically any distance behind the slit where it will fit without fouling on anything...however if the source is very close...like the side of a fluorescent tube right up against the slit, then there will not be a "blade" of light behind the slit, but rather a "wedge" of light...with the "thin edge of the wedge at the slit" and getting wider as you move further back....so better resolution is obtained by getting the CD/DVD as close up behind the slit as you can....in reality it will be a trade-off between these two extremes. As I say, just try it and see of your results ar good ir crappy...if crappy, adjust it and try again and keep iterating around until you cannot improve the results any further...then you have reached the limits of the technique.

(By "crappy" I mean contaminated with unwanted light, low contrast or low resolution, or any combination of these.)

As for the "inter slit/slot" all it is for is to stop unwanted light sources contaminating your spectra. I will elucidate..

Imagine there are two streetlights down the road outside your window, a clear merc and a high pressure sodium...lets say you want the spectrum of the sodium one....when you point the spectroscope at the sodium one, a blade of sodium light travels down the Pringles Can parallel to the long side of the can, (when you aim it directly at the sodium streetlight), it then impinges on the CD and gives you the spectrum you are after...BUT, the clear merc...angularly close to the sodium, produces a second blade of (blue mercury) light that also travels down the Pringles Can, but at a slight angle to the can's axis....if the can were long enough...like a rifle barrel, then it would eventually hit the side of the can (presumably painted black) and be lost and thus not interfere with the sodium spectrum you are taking...but making the unit long like a rifle barrel presents all sorts of other issues...so getting rid of that blade of mercury light and preventing it getting to the CD is the goal....and that is what the inter-slot is for.

It dosn't really matter of the slit is not right on the axis of the can, but if it were right near the edge it would be difficult for it to get to the CD easily...the blade of light only needs to get to the CD and as long as there is some CD either side of its impingement point, that is all that matters. If you wish to place the slit so the centre of the slit corresponds with the centre axis of the can, go ahead, it won't make much difference to the final result...but if you are that "obsessive-compulsive" sort of person where everything needs to look "just-so" then do it "just so"...otherwise, just aim for getting a spectrum.

The purpose of the Pringles Can is twofold:-

1: to keep extraneous and unwanted light off the CD.

2: to hold the CD firm with respect to the slit and camera

That is all.

Manufactured articles should be made to be used, not made to be sold!

Fee, Fye, Fow, Fum, A dead man's eye and a parrot's BUM!

dor123
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Aug 06, 2019 at 11:45 PM Author: dor123
This is very hard to me to build by own spectroscope. This is a project for me, and I don't so creative.

I"m don't speak English well, and rely on online translating to write in this site.
Please forgive me if my choice of my words looks like offensive, while that isn't my intention.

I only working with the European date format (dd.mm.yyyy).

I lives in Israel, which is a 230-240V, 50hz country.

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Aug 07, 2019 at 02:13 AM Author: Globe Collector
If you continue to do the same things over and over and over, you cease to learn and "expand" as a person, you become stick, like a hamster in a wheel going round and round...but not really getting anywhere.

I cannot believe this simple project is beyond your abilities. If you fail at the first attempt...no problem, try again and learn from the mistakes you made in the first attempt. The materials are cheap and easily obtained. Apart from the razor blade slit, this is something Primary School children could do with cardboard and paper mache.

I explain the assembly of the slit in detail HERE.

Building it will expand your abilities, using it will also allow you to go far further than you are currently able....but do it soon, because LEDs are coming and their spectra are not interesting at all.

Manufactured articles should be made to be used, not made to be sold!

Fee, Fye, Fow, Fum, A dead man's eye and a parrot's BUM!

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