Convoy z1 Aspheric with a 519a.
https://www.aliexpress.us/item/2255801050953923.html?gatewayAdapt=glo2usa4itemAdapt
Really small led with high cri and compatibility with often used 3535 sized accessories could be Luminus SST-12 in 4000K? Neutral bin available at least from here
2 Thanks
I think this is probably the best option. Small emitter, very high CRI, and good compatibility with all sorts of optics. Also, can just order one on a MCPCB already so no reflowing required.
1 Thank
Forgot about this! If maximum output is not a priority then this is the best option for producing a tight beam.
Thanks for that link. I like how small it is, and also how cheap. The datasheet spectrum seems to show quite a dip around 480-500 nm, but I guess that’s just the way it is with these devices.
That’s the wrong datasheet, WxS is the cold white 70CRI version.
WxH and WxH Gen2 are the ones you need.
…sorry, you did say the 4000K version. I see the SST-12-WxH at 4000K does have
a much better looking spectrum, so that looks like a winner to me.
Oh, looks like we both sent the same pic at the same time 
Out of curiosity, as someone who graduated in nanophotonics (msc in Physics), what are you about to do with these LEDs? Can you share some more info?
Just a hobby project I’m doing for my own amusement. I got an old Ocean Optics 360-1000 nm mini-spectrometer and wanted to have some fun with it. Currently I’m looking at how plant leaves have different ratio of Chlorophyll B and other pigments, vs Chlorophyll A, and maybe how that changes over time with conditions. There are some standard light sources sold for these, of course, but they are more than I need and sold for more than I want to pay, so I thought it would be fun to try to make my own on the cheap.
2 Thanks
Oh this is such an interesting project!
I once made some mint juice that is green in low concentrations but deep red in very high concentrations, and was wondering why it happened. My best guess for an explanation is that Chlorophyll B is almost transparent to deep red while being slightly absorptive to green wavelengths, and strongly absorptive to all other wavelengths. At low concentrations the human eye’s much greater sensitivity to green (compared to red) overwhelms the slightly greater transmission of deep red, hence the green appearance. At higher concentrations, however, the transmission spectrum is raised to correspondingly higher powers, so the amount of any wavelength remaining drops off exponentially. So despite the slight initial difference in transmission, the amount of green present in the spectrum drops off rapidly while red is relatively unaffected, and in the limit only deep red remains in the spectrum and is seen by the eye. After reading about your project I’m thinking maybe there is some way to infer the relative concentrations of the chlorophyll variants by looking at the limiting spectrum at very high concentrations–from the plots I see online, the domain of full transmission for Chlorophyll A is right-shifted by 20nm or so compared to Chlorophyll A, and this 20nm should be visually significant as this region is at the right tail of the human eye’s luminosity function.
Since you are studying chlorophyll I’m guessing that deep red emission would be important to have, fortunately the SST12 in 4000K has plenty of that. The light I shone through mint juice had an SST20 in 4000K, which has an identical spectrum.
That sounds like a really cool project. Also, a proper spectrometer in your home lab - damn. I’m jealous ^^
Will you share us some of your results when you got the setup up and running? I’m curious to see it.
What’s your plans regarding driving the LED? My personal recommendation would be not to use a dedicated led flashlight driver, but some step down standalone LED driver with a potentiometer - set it up once, and it will just always drive the led at the same current as soon as you turn the power supply on.
Add a big heatsink (old CPU cooler from a PC maybe? If you have enough space, those can cool your LED while being dead quiet with their large slow fans) and whatever optics you plan on using. If you want a collimated beam, my best guess would be some aspheric lenses as found in regular lab supply. Flashlight optics are not made for collimating, so probably not my first choice for something like this.
1 Thank
A slight concern of mine regarding aspheric lenses is that they don’t collect the light emitted sideways by the LED, so the resulting emission spectrum would be very blue-heavy and pink-colored. (For context, an LED’s emission spectrum, unlike that of an incandescent bulb, changes depending on the viewing angle.) But if you happen upon an LED sample that is more green-tinted then the effects might cancel out. Or maybe the balance of different colors won’t matter for your application, and as long as all wavelengths are present in reasonable quantities everything is fine.
If you’re interested, I have some data from my existing light setup, relying mostly on a traditional filament bulb (mine has not much blue; also drifty). https://photos.app.goo.gl/sovaAdw6NzmBuwzP7
Mostly I’m looking at absorption spectra to tell apart the different leaf pigments, but chlorophyll is also interesting because it has a strong red fluorescence around 665 nm, if you pump it with strong blue light. The difference between the excitation-response curves for the chlorophyll A and B versions let you tell (in theory anyway) what ratio you have. I’m using leaf extract alcohol solutions, but apparently, you can even measure how much photosynthesis work the chlorophyll is doing in a leaf. Relatively more fluorescent output for a given input, means less of the light energy is being used inside the chloroplast for getting stuff done.
1 Thank