TSP #38 - Teardown, Upgrade and Experiments with a Verity Visible Wavelength Monochromator

[@AI7KTD]

Hands down one of my favorite videos of your channel! Thank you for putting in all that effort and sharing the results.

[@microtrigger]

I have got same but bigger monochromator for restoration and automation. What is software are you using to make a plots? Had you calibrated scale with laser or you just fits with exact settings?

[@Thesignalpath]

Yes, just calibrated with a known laser.

[@matthewghali2987]

Amazing work! I am very impressed with the machining. Most electronics guys would slot the mounting holes for the stepper to align its shaft, but you went with micro-adjustable optical stage. Thats a little bit bonkers! Also matching shafts, most folks would have joined them with a short length of rubber tube, but the machined adaptor was very nice! I might be concerned that it could be a little too stiff to isolate enough off-axis motion. The attention to detail on a little side project is really impressive! Apologies for the reply 3 years late- I've just started watching your entire series in chronological order for fun, after skipping around many of your later videos. Enjoyed them all so far! I hope you continue doing a few optical and laser projects mixed in with the RF work. The laser gear available from surplus stuff on ebay is always fun to hunt around for.

[@TheHuesSciTech]

I think it's more common practice to calibrate these things on a "known" source, rather than trying to multiply photomultiplier quantum efficieny * gain function(photomultiplier voltage) * efficiency(mirrors) * efficiency(grating) * attenuation(fibre) * actual slit width, etc etc. Far easier and more accurate just to measure it than try calculate it piecemeal. Furthermore, for spectroscopic applications, you just measure the lightsource, and then add the sample and measure again. Divide latter by former, you have a transmission plot in % which is just what you want in many cases.

[@trickyrat483]

Fantastic little project. Well done. Enjoyed watching this a lot. Glad to see it turned out so well in the end. Some beautiful plots you got from it.

[@ToniT800]

That reminds me my Bachelor Thesis about Characterisation of CdSe single photon emitter:) (I study NanoOptoelectronics) You can excite some semiconductor probes with lasers and observe its emission spectrum. By this you can make assumptions about its band gap, quantum structure (different energy levels => separate peaks in the emission spectrum) and density of states (The amplitude of peak will tell you about how much states are present around particular energy level). You can also perform pulsed measurment to see how long does excited electrons (excitons) "survive" in the semiconductor before optical recombination. A video about this stuff will surely be very educative and interesting to watch.

[@ekarademir]

Just a note, "density" is not entirely related to the refractive index. It is generally used interchangably but it is not correct in terms of electromagnetics. Refractive index is related to the electric dipole distribution inside the material. Of course this would be harder to explain. However, please refrain from using "density" and "refractive index" as similar things. Love your videos, learned a lot from them. Thank you!

[@rogerbreton6412]

Wow! Thank you so much for taking the time to explain and demonstrate! Wow! Wow! Wow!

[@GregorOttmann]

Thanks for the little comment about the Dremel stand - I had actually thought about buying that thing and I am really happy about the warning.

[@nraynaud]

I stumbled on a youtube video comparing stands, and the conclusion about the dremel one were also that it's not good and wobbly.

[@Thesignalpath]

I had a really hard time with it. Very disappointing tool.

[@nraynaud]

maybe it's time to create a support group :)

[@Thesignalpath]

nraynaud1 It is a good idea! Support group for people with emotional trauma due to Dremel stand. (SGPETDDS) for short.

[@hpux735]

I agree about the dremel stand completely. I've had one for quite some time (to drill holes in etched PCBs), and it's very poorly made. I use a harbor freight drill press now, and it's a lot better.

[@HiskoArt]

The emission spectrum from the white LED looks for me like a spectrum from phophor-based white device. So basically you have blue/UV LED with yellow phosphor not the multiple junctions as presented in the video.

[@DaveCurran]

Nice project, particularly the flexible stepper motor coupling, I hadn't seen that idea before.

[@ExtantFrodo2]

First, let me say what an excellent video. If that "white LED" had a flat profile it would not appear white to our eyes which have their own receptor response curve. I'm pretty sure that for doing absorption spectroscopy you would not need to calibrate the PM tube. You simply need to subtract the spectrum from the raw source from the source+sample to get the values for the sample alone.

[@georgeyork8975]

Really nice presentation. Was wondering if you have ever looked at the Verity SD100 Monochromator?

[@GregorOttmann]

After watching the whole thing I must say that there simply aren't enough thumbs one can erect on KZbin. The mechanical part is pure engineering porn, especially with the stepper motor moving along that slide. I actually rewound that part of the video at least 5 times because I couldn't get enough of it. It's such a pity that I don't have any use whatsoever for an instrument like this ...

[@cthree87]

Another excellent video! I was thinking about doing a stepper motor project earlier today, seeing yours is inspiring.

[@rysend]

Very cool project, and excellent presentation, consistent with anything that comes out of your lab. Big THANKS!

[@DanielPierce]

Or a "Helical flex/shaft coupling", depending on the manufacturer.

[@pas3n7]

Shahriar, you are the coolest.

[@MichelPASTOR]

Very nice devices and nice mod. I was curious about the UV content of CFLs. Thanks for the video !

[@DougFeigelson]

I'm surprised the pan you covered it with didn't emit any IR?

[@Coolkeys2009]

Geez you seem to go higher in frequency every week, What's next a spectrum analyser that goes from x-rays to cosmic rays LOL. Great video loved the combination of science, electronics and programming to build a scientific instrument.

[@chuckvanderbildt]

I'm curious if order overlap is not a concern for this design, as i do not see any sequential filters? Would the intensity of the higher overlapping order be so low as to not be a concern?

[@kalhana_photography]

I use the same Dremel drill and stand and use their speed clic cutting discs. I agree that it's very difficult to cut with that setup. Although it's really good for drilling PCBs.

[@Kryoclasm]

Fantastic video! Maybe you could take it to an observatory and measure the spectrum of some stars or even sunlight?

[@TunioMir]

How did you limit the rotation of the stepper so it didn't move the micrometer too far, I'm assuming it has more than enough torque to do some damage

[@AnalysIR]

You could add a fixed colour spectrum gradient as an image under the x-axis as a visual aid when the graph is being drawn! Pity it doesn't go as far as 940nm for IR remote control LEDs, would love to see a plot of different IR LEDs. Yet Another excellent video from TSPB Tnx & Greetings from Dublin, Ireland.

[@AureliusR]

Aha! So you went to UofT. If you're still in Toronto, you should have a meet-up so we can ask you questions and have a couple beers! I'm about to start EETech at Seneca, would love to ask about UT as I want to transition there post-grad.

[@nraynaud]

very good and interesting, thanks. For your coupling, you might be interested in the concept of "spline coupling" which is mechanically a bit simpler (it simply moves the rail in the rotating part, so your motor mount is sturdier). I really dig your videos. I can spend hours passively looking at a moving screen while eating junk food and not feel guilty about getting dumber by the minute.

[@Richardincancale]

In the diagram at the start of the video why does it refer to incident and diffracted rather than reflected wave?

[@Keith_Ward]

This is all fine and great but .... where's your cat? All kidding aside, this is a very nice adaptation of a manual instrument to an automatic or semi-automatic version. You really did a great job here. Maybe you had someone or a machine shop make the micrometer collar adapter with the built-in helical motor coupler?

[@o.denizulus9062]

Can you combine the visible range readings together to form a single color,and check if it matches with the color from the light source. it'll be a cute little validation for the process.

[@darkobul1]

I bet you could use NEMA11 for that application to reduce size of stepper motor. And using 256 micristep driver would add to resolution.

[@CaptiveReefSystems]

You lucky bastard ! 😲 What a find...

[@SciDOCMBC]

phenomenal work, really great, thx for sharing

[@mbabaeevideos]

Thanks Shahriar. I really enjoyed this experiment.

[@prabhnoorkainth1520]

Wow I've been watching your videos for quite some time now and I didn't know you studied at UofT! I'm also doing computer engineering here as well. Thanks for these awesome videos and keep up the good work!

[@DaruoshAghajaney]

excellent project and an amazing experience. thanks man.

[@andreasberger3155]

How close is the measured wavelength of the tiny mercury-peak to 254 nm ? BTW: Thanks for your great and instructive videos.

[@kristhetrader5029]

Very very nice hack and excellent tutorial, keep them up mate!

[@chimawizzle]

Very nice video. Just a couple comments/question: When you talk about the incandescent bulb, you mention the shape has to be corrected by by the QE of the PMT. However, for the 2nd peak in the IR, you make note of it, but don't go into detail. It seems that a likely cause is a grating anomaly (spike in grating efficiency). I would expect the actual shape of an incandescent source to follow a blackbody spectrum pretty closely. Any thoughts on this? Which would bring me to my next question - do you know how to measure the grating efficiency for a given monochromator setup? I am trying to quantitatively measure electroluminescence of a diode and have so far accounted for the QE of the PMT. However, I only have the manufacturer's grating efficiency for a Littrow configuration, and my monochromator has an unfolded Czerny-Turner configuration. From my understanding, the efficiency can change significantly based on the configuration used.

[@imamkusnendar]

where is the code for your stepper? and detils about your works? thank you.

[@leppie]

Yes, I actually went to read about it not so long ago. My head hurts thinking about it. ;p (time passes) WOW, that is an awesome score! One question, why did you refrain from mentioning spectrometer at all during the video? From my layman's view, they look the same.

[@tiittalts3944]

very intereting video , i liked it. if i had this device and some more stepper motors i would tray do make night vision camera or uv camera.

[@razean22]

You've been to the UofT? That's very cool! I've been an exchange student at Ryerson and people always said that's where the students go that UofT did not accept ^_^ (Glad to be back in Germany now, Toronto is at -14°C in the night whereas my town is around 4° even though being on a similar latitude)

[@pakforce]

Super cool video...

[@vidasvv]

Another great video, TNX !!!

[@turbochargedbrick]

The results are great!

[@Dyas777]

Can you connect that device to a telescope to see the spectrum of stars?

[@Regular6782]

Thank you for the video mate, love watching them and I always learn a lot. Just out of curiosity, I used to work with nuclear density gauges and they also used photo multiplier tubes to measure the radiation passing through a specific material, hence giving density. Do you know if they use the same style of tube, or will there be a different material at the front for the cathode?

[@totbenru]

Absolute Genius.

[@sunoj]

Awesome video i liked it

[@zuccasnow]

Take a RGB Led or something else to create a variable wavelength light source but always with the same amplitude. It would be interesting to see how your human eyes is sensing power/brightness in the different nm. You certainly know that a human ear has not a flat sensibility... may the eye too.. Didn't google yet...

[@UKLifeCoaching]

Wonderful stuff. Thanks!

[@batterydudellc961]

Very interesting video! Thanks for the upload I learned alot..

[@deniselee1900]

Hi, would you be able to make a lab grade comparison with the Hamamatsu microspectrometer and TAOS TCS230? To ascertain the accuracy of the two (or rather are they good enough?), both are most likely cheaper and more accessible to hobbyist. TCS230 is a popular colour sensor, but it provides readouts in radiant power. A cheap open source grow light photosynthetically photon flux density (PPFD) meter on a Arduino platform is a great idea.

[@One-jz6sl]

Can I get the software you designed for this unit at a price? Schematics?

[@One-jz6sl]

No response, none. Only 77 comments and you can't answer? You must be a very busy successful guy, those are the kind of people who don't have time to help.

[@catx]

Very interesting.

[@mrlazda]

I am wondering why people in USA and Canada confuse First law of thermodynamics with Law of conservation of energy. First law of thermodynamics is subset of Law of conservation of energy limited to use for thermodynamic systems.

[@TheConnorGames]

The PMT may be a Hamamatsu R928HA. See www.repairfaq.org/sam/laserlia.htm#liamono

[@DavidMG99]

👍👍

[@thecandlej]

Great Video as always! For my bachelor thesis I have worked with con-focal chromatic displacement sensors that can measure very fine displacement (1/10 of a micrometer) and thicknesses of transparent materials. I know the working principle of it is the the spectral analysis of a reflected wavelength through a chromatically uncorrected lens. As shorter wavelengths are focused at shorter distances to the lens and longer wavelengths get focused further away. By analysis of the content of the reflected light, one can tell the precise distance the source is away from the material. Maybe you could do something similar to this www.laserage.ie/files/OP0002_chromatic_confocal_operating_principleV2.JPG Anyways, thank you for the interesting and informative videos.

[@vampifrog]

Analyze sunlight!

[@TheBarretNL]

When he says "Pretty straight forward" (a lot btw!) its not straight focking forward for me :P