Unique Titanium
Results 1 to 19 of 19

Thread: High power thru-hole LED

  1. #1

    Default High power thru-hole LED

    Hi,

    I'm looking for ultra bright thru-hole LEDs for my research, but am new at this whole thing. For my application, I want to place one linear LED array on each side of the forearm and image through the skin layer. I need the light to be powerful enough to go through thick biological tissue while not being harmful. As far as I've learned, heat seems to be the only source of potential danger, so I'm guessing that a heatsink would solve this problem?

    Since I have only rudimentary experience with LEDs, what kind of power and/or radiant intensity would you recommend? Currently I'm using an array of fifty 5mm thru-hole 80mW/sr LEDs and its not nearly enough, so I need brighter ones (assuming brightness is the determining factor here).

    What are the advantages and disadvantages of thru-hole versus surface-mount? The device is size-sensitive (cost not so much), and I will be hand-soldering the arrays.

    Finally, is there any advantage at all of using laser diodes over ultra-bright LEDs? As far as I'm aware, the main differences are collimation and coherence, and neither attribute is relevant here.

    Again, I apologize for the beginner questions, and thank you for your time.

    -Alvin

  2. #2
    Flashaholic* LEDAdd1ct's Avatar
    Join Date
    Jul 2007
    Location
    Hudson Valley
    Posts
    3,097

    Default Re: High power thru-hole LED

    I would love to see beamshots of this once you get off the ground!
    "...and the diode multiplied and grew in brightness. And God saw that it was good."

  3. #3
    Flashaholic* AnAppleSnail's Avatar
    Join Date
    Aug 2009
    Location
    South Hill, VA
    Posts
    3,979

    Default Re: High power thru-hole LED

    Do you have any idea how much light you need? I can see large blood vessels with a decent flashlight on my skin. Your eyes glow if you put one in your mouth. There are some very bright LEDs out there, and wire-and-go constant-current drivers. Does color rendering matter?
    My biggest light-hog is my camera.

  4. #4
    Flashaholic*
    Join Date
    Jan 2004
    Location
    Pleasanton (Bay Area), CA, USA
    Posts
    3,593

    Default Re: High power thru-hole LED

    Hi, I have played with this kind of imaging and it is quite fun.

    The absorbtion of most light wavelengths is quite high, so it is useful to concentrate on the 600- 650nm range. LEDs are quite bright around 615 - 620nm, so this is useful.

    Surface mount LEDs are much more able to dissipate heat, so that is a good place to look.

    To look through your hand, it takes about 5 - 10 K lux. To go through your arm, a bit more, probably something like 100 - 300K lux.

    I am not sure that you can be certain that this kind of power level will have no effect without some testing, as it starts to approach power levels that could disrupt cell walls.
    Homebuilts - "BREEZE" RCR2 sidexside, "Tornado" 4 x 18650 side x side, Streamlight SL20x LED module (Custom BST Feeler Thread)

  5. #5
    *Flashaholic* fyrstormer's Avatar
    Join Date
    Jul 2009
    Location
    Northern VA, USA
    Posts
    5,732

    Default Re: High power thru-hole LED

    LED-TECH.de sells 500mW thru-hole LEDs. You'll need to provide some means to connect the wire leads to a heatsink though, if you're going to run them that hard.

    Surface-mount LEDs are more efficient, though. Is there a reason you can't use a bunch of them instead?

  6. #6

    Default Re: High power thru-hole LED

    I see an inherent problem with using visible light for this type of imaging. Human tissue (obviously) absorbs quite bit of light, and while it's easy to illuminate soft tissue enough so see surface veins with a moderate light source, it sounds like you're going to need something very bright. The problem with this is that as you increase the amount of visible light on your arm, you also increase the amount of energy that is being absorbed and converted to heat. If you concentrated enough light on your arm to go all the way through, you may cause deep burns.

    I also don't think that thru-hole LEDs will be able to produce this kind of light, though there are some very high power (and expensive) LEDs available in a TO-66 package that might be capable.

    Then again, I don't think I fully understand what your goal is, and this may all be irrelevant. Something to think about, anyway.

  7. #7
    Flashaholic Apollo Cree's Avatar
    Join Date
    Nov 2009
    Location
    United States of America
    Posts
    451

    Default Re: High power thru-hole LED

    I don't think using a laser gives you any advantages. Laser LEDs are usually less powerful and efficient than visible lasers.

    Some of your heat concerns will be less if you design your system to be low duty cycle. i.e. Set things up, press a button, the lights come on for 1 second, you take a picture, then the lights shut off.

    Depending on what you're doing, the color of the LEDs may make a big difference. Contrast and penetration will probably be much different for a red LED vs. a blue LED. There might be some "magic" wavelengths that work best. What are you trying to image? Blood vessels, bone, alien abductee tracking devices?

    Your best bet may well be a commercial camera strobe light. Be careful the first few times you use it. Some of them might be powerful enough to cause a burn. It's easy enough to buy a strobe and make a quick test.
    If once you start down the light path, forever will it dominate your destiny, consume you it will.

  8. #8

    Default Re: High power thru-hole LED

    Thanks so much for your help! I probably should have been more clear about the application.

    We're trying to image veins for a venipuncture-assist device. Many studies have shown that infrared light provides the best balance of light penetration depth and hemoglobin absorption, so I'm looking at the 850-950nm range. 600-650nm is best for the superficial smaller vascular structures, but the large deep veins used for venipuncture require longer wavelengths.

    Quote Originally Posted by fyrstormer
    Surface-mount LEDs are more efficient, though. Is there a reason you can't use a bunch of them instead?
    The only reason I was hesitant to use surface-mount LEDs was because I have no experience soldering them, whereas I've soldered thru-hole arrays before. But if it's possible to hand-solder SMDs, and if they have better heat dissipation, then they may very well be better than thru-hole.

    Quote Originally Posted by HarryN
    To look through your hand, it takes about 5 - 10 K lux. To go through your arm, a bit more, probably something like 100 - 300K lux.
    Thanks for these numbers, they'll be very helpful. Only thing is, in the IR I can't use lux since it's invisible (and conversion to irradiance is difficult because luminous efficiency of the human eye for IR is zero). Do you have an idea of the irradiance equivalent of 100-300K lux?

    Quote Originally Posted by Apollo Cree
    Some of your heat concerns will be less if you design your system to be low duty cycle. i.e. Set things up, press a button, the lights come on for 1 second, you take a picture, then the lights shut off.
    Yeah we're most likely going to strobe the lights to match the exposure time per frame of the video camera. For 10 frames-per-second acquisition, I can probably get away with a duty cycle under 10%.

    Thanks again everyone for helping a newbie out.

  9. #9

    Default Re: High power thru-hole LED

    camera strobe light. Be careful the first few times you use it. Some of them might be powerful enough to cause a burn.
    Be REALLY careful with strobes...


    If you like to take pictures of Blood vessels, infrared would work well, i guess. But you need a camera that captures the ir-spectrum. normal ones have an ir-filter.

  10. #10

    Default Re: High power thru-hole LED

    These seem interesting:

    http://www.magnalight.com/p-47292-in...-or-940nm.aspx

    They also come in arrays of 12, 16, or more LEDs.

    SPECIFICATIONS:
    Length: 6.35 inches
    Height: 3.25 inches; 5 inches w/ Trunnion Mount
    Depth: 3.5 inches
    Weight: 3.2lbs
    LEDs: 8
    Each LED Watts: 3 Watts
    Total Watts: 24 Watts
    Volts: Operates on 9-42 Volts DC; including 12 and 24 Volts
    Amps: 2 amps on 12 volts, 1 amps on 24 volts
    Lumens: 1440
    IR Wavelength: 850nm or 940nm
    Housing Color: black or white available
    Ambient operating temperature range: -40 degrees C to 85 degrees C


    LUX Measurements (FLOOD):
    At The Lens: 185,800
    At 1 Meter: 2,672
    Lens Temperature: 78 Degrees F


    LUX Measurements (SPOT):
    At The Lens: 190,400
    At 1 Meter: 8,440
    Lens Temperature: 77 Degrees F


    Only thing is that they don't strobe so it goes to 77 degrees at the lens.

  11. #11
    Flashaholic*
    Join Date
    Jul 2010
    Location
    Sydney, Australia
    Posts
    995

    Default Re: High power thru-hole LED

    For better heat-sinking without needing to surface-mount solder, you could buy 3 watt IR LEDs mounted on aluminium stars.

    Just screw them onto your heatsink.

    The Dealextreme sku.14061 ones only cost $7. They draw 1.5 amps at 2 volts, but you could under-run them to reduce the heat at each LED.

  12. #12
    Flashaholic*
    Join Date
    Jan 2004
    Location
    Pleasanton (Bay Area), CA, USA
    Posts
    3,593

    Default Re: High power thru-hole LED

    The key to easy surface mount soldering of LEDs is to use a quality solder paste and a hot plate / heating from underneath.

    Modern LEDs usually can take lead free solder temperatures, but I prefer to use lead based solder, especially for proto work. This gives you a much wider margin of error, which is common in hand assy. work.

    The nature of solder paste lifetime is that you usually have to buy direct from the mfg or a close knit distributor.
    Homebuilts - "BREEZE" RCR2 sidexside, "Tornado" 4 x 18650 side x side, Streamlight SL20x LED module (Custom BST Feeler Thread)

  13. #13

    Default Re: High power thru-hole LED

    Quote Originally Posted by AnAppleSnail View Post
    Do you have any idea how much light you need? I can see large blood vessels with a decent flashlight on my skin. Your eyes glow if you put one in your mouth. There are some very bright LEDs out there, and wire-and-go constant-current drivers. Does color rendering matter?
    i saw the area under my eye _sockets_ glow when i put a bright flashlight in my mouth. how do you get the eye to glow when the whole purpose of the sclera et al is to retain a black environment?

  14. #14
    *Flashaholic* fyrstormer's Avatar
    Join Date
    Jul 2009
    Location
    Northern VA, USA
    Posts
    5,732

    Default Re: High power thru-hole LED

    Quote Originally Posted by haserman View Post
    i saw the area under my eye _sockets_ glow when i put a bright flashlight in my mouth. how do you get the eye to glow when the whole purpose of the sclera et al is to retain a black environment?
    Nothing is perfect. Eyes have never had to deal with bright light coming from *inside* the skull in the middle of the night before. The sclera is good enough to block enough light to keep your vision perceptually glare-free when the light outside the skull is brighter than the light inside, which is all *normal* people ever need.

  15. #15

    Default Re: High power thru-hole LED

    oh, man. this i gotta see. i tried, but i'm not able to get my eyes glowing from the inside. what power light and where did you point it? it would be awesome for halloween.

    Quote Originally Posted by fyrstormer View Post
    Nothing is perfect. Eyes have never had to deal with bright light coming from *inside* the skull in the middle of the night before. The sclera is good enough to block enough light to keep your vision perceptually glare-free when the light outside the skull is brighter than the light inside, which is all *normal* people ever need.

  16. #16
    Flashaholic*
    Join Date
    Jul 2008
    Location
    Tucson, Arizona
    Posts
    824

    Default Re: High power thru-hole LED

    Quote Originally Posted by haserman View Post
    oh, man. this i gotta see. i tried, but i'm not able to get my eyes glowing from the inside. what power light and where did you point it? it would be awesome for halloween.
    I've found it works best on leaner people. My eyes glow like bright embers when I did that with my Oveready triple. It also works best with lights that are almost pure flood, rather than a light with a reflector.

    https://sphotos.xx.fbcdn.net/hphotos..._2981520_n.jpg

    You could even see most of the veins in my face (this was taken with a camera phone, so you can't see it all that well)! If you're looking at it on an LCD monitor, look at my left eye (the one on the right in the pic), and you'll see several veins.

    I need to get another really bright light like that again.

  17. #17

    Default Re: High power thru-hole LED

    Quote Originally Posted by bstrickler View Post
    I've found it works best on leaner people. My eyes glow like bright embers when I did that with my Oveready triple. It also works best with lights that are almost pure flood, rather than a light with a reflector.

    https://sphotos.xx.fbcdn.net/hphotos..._2981520_n.jpg

    You could even see most of the veins in my face (this was taken with a camera phone, so you can't see it all that well)! If you're looking at it on an LCD monitor, look at my left eye (the one on the right in the pic), and you'll see several veins.

    I need to get another really bright light like that again.
    That's an incredible shot from a camera phone, looks like thermal imaging!
    How long till the soft palate & tongue become medium rare with that Oveready triple?

  18. #18

    Default Re: High power thru-hole LED

    i got the same result you did with my very bright flashlight. that's just the underside of the eye socket, not the eyeball itself. though i was able to see "light" in my eyes in a dark room when i put the flashlight in my mouth and aimed at its roof. just didn't see light coming out of my eyeballs, pupils or anything else.

    Quote Originally Posted by bstrickler View Post
    I've found it works best on leaner people. My eyes glow like bright embers when I did that with my Oveready triple. It also works best with lights that are almost pure flood, rather than a light with a reflector.

    https://sphotos.xx.fbcdn.net/hphotos..._2981520_n.jpg

    You could even see most of the veins in my face (this was taken with a camera phone, so you can't see it all that well)! If you're looking at it on an LCD monitor, look at my left eye (the one on the right in the pic), and you'll see several veins.

    I need to get another really bright light like that again.

  19. #19
    Flashaholic*
    Join Date
    Jul 2008
    Location
    Tucson, Arizona
    Posts
    824

    Default Re: High power thru-hole LED

    Quote Originally Posted by haserman View Post
    i got the same result you did with my very bright flashlight. that's just the underside of the eye socket, not the eyeball itself. though i was able to see "light" in my eyes in a dark room when i put the flashlight in my mouth and aimed at its roof. just didn't see light coming out of my eyeballs, pupils or anything else.
    I saw a REALLY bright red light when I did that, and it actually hurt due to how red it was.

    Quote Originally Posted by Up All Night View Post
    That's an incredible shot from a camera phone, looks like thermal imaging!
    How long till the soft palate & tongue become medium rare with that Oveready triple?

    I only got it to a nice rare before my mouth filled with saliva
    Mag 1D, 2DL, 3DL, 6D hotwire+extension... Fenix E15... Surefire Z2, E1e, 6P, U2 modded with T5 XM-L... Just to name a few

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •