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Thread: Help with designing a custom LED apparatus

  1. #1

    Question Help with designing a custom LED apparatus

    hi guys,

    i'm interested in building a LED apparatus similar to one described in a paper:

    670nm light devices were based on simple commercial DC torches with ten 670nm LEDs mounted behind a light diffuser embedded in a tube that was 4cm in diameter. Energies at the cornea were approximately 40mW/cm2 which often resulted in a mild green after image for approximately 5-10 seconds. Participants were asked to use the light to illuminate their dominant eye every morning for 3 minutes and to repeat this daily for 2 weeks.
    i'm familiar with basic electrical concepts, soldering, fundamentals of driving LEDs, etc. for example, i know that i could make a basic analog DC design perhaps using a 9V battery, a potentiometer, and maybe some resistors to bring the current draw into the desired range for the diodes based on their voltage drop.

    but i'm more interested in making this thing not a clunky piece of junk on a breadboard and would opt for off-the-shelf components if available.
    and so i'm looking for recommendations on drivers, ~670nm LEDs (should i go with strips?), and housing (including diffuser material) to simplify design. really, any suggestions on materials would be appreciated. making it 18650-based would be a bonus since i have a bunch of those already.

    unfortunately, i don't have a picture of the apparatus used in the paper, but i think the idea is to have a fairly wide, even glow that occupies a lot of your field of view. so the LED strip idea may or may not work depending on the diode density and how well a diffuser works. maybe i'd end up going with two or more rows of LED strip. depending on price and availability, i'd even be open to a COB emitter since i guess that would be pretty even and would simplify things.

    one requirement is pretty decent output adjustment. i'm not staring directly into bright LEDs.
    and preferably not via annoying, low-frequency PWM. if it uses PWM, it should be high enough frequency to not be perceptible even with a little bit of motion.

    for those curious, here's the paper:

    Optically improved mitochondrial function redeems aged human visual decline
    Harpreet Shinhmar, MSc, Manjot Grewal, BSc, Sobha Sivaprasad, MBBS, PhD, Chris Hogg, Victor Chong, MBBS, PhD, Magella Neveu, PhD, Glen Jeffery, D.Phil

    https://sci-hub.tw/https://academic....laa155/5863431

    Mitochondria have specific light absorbance characteristics influencing their performance. Longer wavelengths spanning 650->1000nm improve mitochondrial complex activity, membrane potential and ATP production. Here we use 670nm light to improve photoreceptor performance and measure this psychophysically in those aged 28 to 72 years. Rod and cone performance declined significantly after approximately 40 years of age. 670nm light had no impact in younger individuals, but in those around 40 years and over, significant improvements were obtained in colour contrast sensitivity for the blue visual axis (tritan) known to display mitochondrial vulnerability. The red visual axis (protan) improved but not significantly. Rod thresholds also improved significantly in those >40 years. Using specific wavelengths to enhance mitochondrial performance will be significant in moderating the ageing process in this metabolically demanding tissue.
    basically, staring into red light for a few minutes a day may significantly improve vision (color discrimination, night vision) in those ~40 years and older.

    thanks!
    Last edited by SYZYGY; 06-30-2020 at 11:35 PM.

  2. #2
    Flashaholic*
    Join Date
    Jan 2004
    Location
    Pleasanton (Bay Area), CA, USA
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    Default Re: Help with designing a custom LED apparatus

    Thanks for the link to the paper. I didn't read the entire paper yet but I downloaded it and skimmed.

    It is interesting that the effect seems to have the highest benefit for ages ~ 45-65.

    I didn't see a photo of their "device" but I wonder if all that is really needed is a flashlight with a 670nm LED. Since efficiency is not the main priority, a variable resistor based setup is fine for the driver. That makes it pretty easy electrically.

    670nm LEDs have a pretty low Vf, so it could be powered really by for example 2 C or 2 AA conventional batteries, or your desired 18650s.

    I think of 670nm as being a very deep red - sort of on the edge of what people can see IIRC.

    I don't have a very good feel for that illumination level and the reason for the optics vs just an open flood beam with no optics.

    You would need access to a specialized light meter or spectrometer to really measure the output level. They are common, but not completely cheap.

    It might be possible to buy a peak flashlight and change the LED? Their design is very easy to adjust the output over a wide range. They are pretty inexpensive so even if it didn't work it isn't a lot of money.

    _______________

    665nm from digikey.


    https://www.digikey.com/product-deta...CT-ND/11200877

    Osram part with multiple colors mounted on a star board. Pretty easy to use.

    https://www.digikey.com/product-deta...188-ND/6619065
    Last edited by HarryN; 07-31-2020 at 11:30 AM.
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