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Posted: 3/18/2014 4:23:26 PM EDT
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I had tried to get some interest in diy led flashlights in the past, but there wasn't any interest back then, so I didn't continue posting. Since it has been a while, here is another simple project, which you can use the general principles and design your own direct drive led stuff. To understand how to use LEDs, you just need to learn some basic principles of electronics, which is serial and parallel resistance, and basic current x resistance = voltage, and how LEDs work - stuff I won't discuss here, as there are plenty of places on the net that discuss it. In this simple design, the led is directly driven thru a resistor from the batteries. This means, it will be very bright, initially, but, as the battery voltage drops, it will start getting a little dimmer, and draw a little more current. In this example, I picked up 850nm, 60ma leds from ebay - from this dealer, you can get 50 for $4. http://www.ebay.com/itm/Lot-of-50-X-5mm-IR-infrared-LED-850nm-Free-Resistors-/370412362808?pt=LH_DefaultDomain_0&hash=item563e4c1c38 for the choice of resistors, I asked for ones for 5volts, and they supplied 47 ohm resistors. From these resistors, I will be powering the led with 3v, so 3v - 1.6v (led drive voltage) / 47 ohm = .03 or 30 milliamps current draw. using nimh batteries, it comes out to 18 milliamps. since this is for close up lighting, this was more than adequate. if you decide you want to build a light with a higher draw, just change the value for the resistor. in this case, to drive the led at 60ma, use a 22 ohm resistor. an estimate of how long a light might last is with a fully charged nimh battery at 2400mah, at 20ma 2400mah/20ma = 120 hours. - most likely, the batteries don't have 2400mahs for a charge, and the useful run time will probably be around 80-100 hours before it gets dim enough to not be useful except really close up. I picked up this cheap flashlight from harbor freight for $1.50 or so.  unscrew the ring around the head of the flashlight. pull out the bulb, which is held in by leads threaded thru a white plastic holder looking at the sides, you see 2 flat pieces of plastic that hold the head on to the pieces of plastic which the head swivels on, one of which is on the circular piece of foam in the above image looking at the flashlight, take the right side (your right) metal contact off the flashlight head, and one side of the metal contact on the bottom of the white bulb holder off. this is the side that is to the positive battery terminal.  use some sandpaper, clean the metal on the end of the metal contact for the bulb, and the metal contact for the flashlight head. solder a short piece of wire to the metal contact as shown, and the resistor to the metal contact for the bulb slip the flashlight head contact back thru the hole in the head, and solder to the other end of the resistor bend up the metal contact on the flashlight head, so it won't touch anything, and put everything back together. the long end of the led, which goes to the positive lead to the battery, slips into the hole in the plastic bulb holder which has the contact soldered to the resistor. put the flashlight lens back on and screw on the ring holding it on, and turn on to test. it will light up an area as a flood, out to about 30 feet. so, for a few bucks for the leds, and resistors, you can convert a lot of different flashlight bodies to ir leds, if you want to play around with things. |
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Nice post.
There are many LED current limiting resistor calculators online, but you give info adequate to make the light perform how the user wants it to. I have made many LED lights and illuminators, too. I join you in recommending the idea to the other guys. There are so many different purposes for lights, and differing distances of interest, especially those between what the NV's LED (which is often too dim) lights up and the reach of the main helmet or rifle light (which is often too bright), that NOT making cheap lights to close the gaps, and there's no reason not to. Well done. |
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Quoted: Oh yeah? Have you looked at a glass of red wine through a NOD? That's the coolest thing I've seen this year. Even better than my alien abduction.  Quoted: Quoted: Um, this may be the coolest post I've seen this year. Oh yeah? Have you looked at a glass of red wine through a NOD? That's the coolest thing I've seen this year. Even better than my alien abduction. You realize now that you're obligated to take a picture and post it don't you?  Regards David |
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You realize now that you're obligated to take a picture and post it don't you?
Regards David Quoted:
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Um, this may be the coolest post I've seen this year. Oh yeah? Have you looked at a glass of red wine through a NOD? That's the coolest thing I've seen this year. Even better than my alien abduction. You realize now that you're obligated to take a picture and post it don't you?
Regards David Yeah, he can't just toss out that tidbit and not provide proof. 
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Quoted:
Yeah, he can't just toss out that tidbit and not provide proof.
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Um, this may be the coolest post I've seen this year. Oh yeah? Have you looked at a glass of red wine through a NOD? That's the coolest thing I've seen this year. Even better than my alien abduction. You realize now that you're obligated to take a picture and post it don't you?
Regards David Yeah, he can't just toss out that tidbit and not provide proof.
Of my alien abduction? Well, all I know is my ass hurts something aweful. |
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Of my alien abduction? Well, all I know is my ass hurts something aweful. Quoted:
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Um, this may be the coolest post I've seen this year. Oh yeah? Have you looked at a glass of red wine through a NOD? That's the coolest thing I've seen this year. Even better than my alien abduction. You realize now that you're obligated to take a picture and post it don't you?
Regards David Yeah, he can't just toss out that tidbit and not provide proof.
Of my alien abduction? Well, all I know is my ass hurts something aweful. This thread is doing just fine without pics. 
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 should have known that this forum has become like gd, since some people have started posting here.... point of posting how to make cheap ir flashlights is so you can make a bunch, and not have to worry about losing them very much. for instance, you make make a couple of them, and use them to illuminate around a feeder at night in heavy woods, where you might get reflections off of brush and stuff, if you were trying to use an illuminator off your rifle. (other applications deleted) |
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Other than applying a filter over the lens or as the lens, is there a way to mitigate the visible spectrum that one of these DIY illuminators produces? Are LED's available higher into the IR spectrum? Pick an LED in the right spectrum, and you shouldn't need one. You can see the spectrum on the datasheets from digikey. Example - spectrum plot is on page 4 |
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Pick an LED in the right spectrum, and you shouldn't need one. You can see the spectrum on the datasheets from digikey. Example - spectrum plot is on page 4 Quoted:
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Other than applying a filter over the lens or as the lens, is there a way to mitigate the visible spectrum that one of these DIY illuminators produces? Are LED's available higher into the IR spectrum? Pick an LED in the right spectrum, and you shouldn't need one. You can see the spectrum on the datasheets from digikey. Example - spectrum plot is on page 4 Ah, that's what I was looking for. So, related, how effective are LED's that are higher into the IR spectrum when used for illumination? Are "typical" I2 devices optimized for a specific wavelength - like say 835nm - and would the higher one moves in the IR spectrum reduce the effective output of an LED when viewed through an I2 device versus one driven at an equivalent wattage but that's closer to the optimum wavelength? |
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Ah, that's what I was looking for. So, related, how effective are LED's that are higher into the IR spectrum when used for illumination? Are "typical" I2 devices optimized for a specific wavelength - like say 835nm - and would the higher one moves in the IR spectrum reduce the effective output of an LED when viewed through an I2 device versus one driven at an equivalent wattage but that's closer to the optimum wavelength? Quoted:
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Other than applying a filter over the lens or as the lens, is there a way to mitigate the visible spectrum that one of these DIY illuminators produces? Are LED's available higher into the IR spectrum? Pick an LED in the right spectrum, and you shouldn't need one. You can see the spectrum on the datasheets from digikey. Example - spectrum plot is on page 4 Ah, that's what I was looking for. So, related, how effective are LED's that are higher into the IR spectrum when used for illumination? Are "typical" I2 devices optimized for a specific wavelength - like say 835nm - and would the higher one moves in the IR spectrum reduce the effective output of an LED when viewed through an I2 device versus one driven at an equivalent wattage but that's closer to the optimum wavelength? As far as the response of the NV unit, my guess is that it has peak frequency responses just like the LEDs have peaks in their output spectra. In the event that it's a simple distribution, generally the interference (overlap) of the two spectra (the response of the nods and the output of the illuminating LEDs) is what would determine the relative brightness that appears to you. At least, that's generally how it works for an emitter/receiver pair. I have to admit, I don't have a deep enough knowledge of NV to say anything for sure
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As far as the response of the NV unit, my guess is that it has peak frequency responses just like the LEDs have peaks in their output spectra. In the event that it's a simple distribution, generally the interference (overlap) of the two spectra (the response of the nods and the output of the illuminating LEDs) is what would determine the relative brightness that appears to you. At least, that's generally how it works for an emitter/receiver pair. I have to admit, I don't have a deep enough knowledge of NV to say anything for sure Quoted:
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Other than applying a filter over the lens or as the lens, is there a way to mitigate the visible spectrum that one of these DIY illuminators produces? Are LED's available higher into the IR spectrum? Pick an LED in the right spectrum, and you shouldn't need one. You can see the spectrum on the datasheets from digikey. Example - spectrum plot is on page 4 Ah, that's what I was looking for. So, related, how effective are LED's that are higher into the IR spectrum when used for illumination? Are "typical" I2 devices optimized for a specific wavelength - like say 835nm - and would the higher one moves in the IR spectrum reduce the effective output of an LED when viewed through an I2 device versus one driven at an equivalent wattage but that's closer to the optimum wavelength? As far as the response of the NV unit, my guess is that it has peak frequency responses just like the LEDs have peaks in their output spectra. In the event that it's a simple distribution, generally the interference (overlap) of the two spectra (the response of the nods and the output of the illuminating LEDs) is what would determine the relative brightness that appears to you. At least, that's generally how it works for an emitter/receiver pair. I have to admit, I don't have a deep enough knowledge of NV to say anything for sure I think we said the same thing, but your response had the benefit of being composed by someone who understands maths and that sciencey stuff. I was a poli sci and history major.
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I think we said the same thing, but your response had the benefit of being composed by someone who understands maths and that sciencey stuff. I was a poli sci and history major. Quoted:
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Other than applying a filter over the lens or as the lens, is there a way to mitigate the visible spectrum that one of these DIY illuminators produces? Are LED's available higher into the IR spectrum? Pick an LED in the right spectrum, and you shouldn't need one. You can see the spectrum on the datasheets from digikey. Example - spectrum plot is on page 4 Ah, that's what I was looking for. So, related, how effective are LED's that are higher into the IR spectrum when used for illumination? Are "typical" I2 devices optimized for a specific wavelength - like say 835nm - and would the higher one moves in the IR spectrum reduce the effective output of an LED when viewed through an I2 device versus one driven at an equivalent wattage but that's closer to the optimum wavelength? As far as the response of the NV unit, my guess is that it has peak frequency responses just like the LEDs have peaks in their output spectra. In the event that it's a simple distribution, generally the interference (overlap) of the two spectra (the response of the nods and the output of the illuminating LEDs) is what would determine the relative brightness that appears to you. At least, that's generally how it works for an emitter/receiver pair. I have to admit, I don't have a deep enough knowledge of NV to say anything for sure I think we said the same thing, but your response had the benefit of being composed by someone who understands maths and that sciencey stuff. I was a poli sci and history major. I think so, yes. My wife was a poli sci/ history double major too. I would ask her to see if she thinks we said the same thing, but she'd probably just swear and roll her eyes at me
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you've both discussed it above, but graphically.... an led doesn't only emit one frequency of light, they are rated by the peak wavelength  wavelength of an osram 850nm led. the various generation night vision devices have sensitivities like this  image orignally posted by dcs in this thread http://www.ar15.com/archive/topic.html?b=6&f=18&t=294085 skypup notes that rhodopsin, the pigment that sees for you, is only sensitive up to 720nm in this thread http://www.ar15.com/forums/t_6_18/414218__ARCHIVED_THREAD____Anyone_have_hogs_spook_when_turning_on_Torch.html&page=1 so what glow you see is light being emitted from the side wavelengths off of the peak. and shows how a cutoff filter, which only allows certain wavelengths of light to get thru, could be used to decrease how visible the glow from an led emitter is. http://www.ar15.com/forums/t_6_18/402460_Hog_reaction_to_850nm_IR.html from the response graph, once you go above 850nm the sensitivity starts falling off really fast. that means, you would need a lot more power at 940nm to achieve the same amount of visual illumination from a gen3 nvd, compared to that at 850nm or lower. so, if you really want to go "covert", with little if any led glow, you'll want to put a bandpass filter on a 850nm led, or get a 940nm at, maybe 4-10x the power, to get the same 'visual brightness'. |
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you've both discussed it above, but graphically.... an led doesn't only emit one frequency of light, they are rated by the peak wavelength http://i57.tinypic.com/9fpbg1.jpg wavelength of an osram 850nm led. the various generation night vision devices have sensitivities like this http://i61.tinypic.com/2442nw0.jpg image orignally posted by dcs in this thread http://www.ar15.com/archive/topic.html?b=6&f=18&t=294085 skypup notes that rhodopsin, the pigment that sees for you, is only sensitive up to 720nm in this thread http://www.ar15.com/forums/t_6_18/414218__ARCHIVED_THREAD____Anyone_have_hogs_spook_when_turning_on_Torch.html&page=1 so what glow you see is light being emitted from the side wavelengths off of the peak. and shows how a cutoff filter, which only allows certain wavelengths of light to get thru, could be used to decrease how visible the glow from an led emitter is. http://www.ar15.com/forums/t_6_18/402460_Hog_reaction_to_850nm_IR.html from the response graph, once you go above 850nm the sensitivity starts falling off really fast. that means, you would need a lot more power at 940nm to achieve the same amount of visual illumination from a gen3 nvd, compared to that at 850nm or lower. so, if you really want to go "covert", with little if any led glow, you'll want to put a bandpass filter on a 850nm led, or get a 940nm at, maybe 4-10x the power, to get the same 'visual brightness'. Nice work! 
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you've both discussed it above, but graphically.... an led doesn't only emit one frequency of light, they are rated by the peak wavelength http://i57.tinypic.com/9fpbg1.jpg wavelength of an osram 850nm led. the various generation night vision devices have sensitivities like this http://i61.tinypic.com/2442nw0.jpg image orignally posted by dcs in this thread http://www.ar15.com/archive/topic.html?b=6&f=18&t=294085 skypup notes that rhodopsin, the pigment that sees for you, is only sensitive up to 720nm in this thread http://www.ar15.com/forums/t_6_18/414218__ARCHIVED_THREAD____Anyone_have_hogs_spook_when_turning_on_Torch.html&page=1 so what glow you see is light being emitted from the side wavelengths off of the peak. and shows how a cutoff filter, which only allows certain wavelengths of light to get thru, could be used to decrease how visible the glow from an led emitter is. http://www.ar15.com/forums/t_6_18/402460_Hog_reaction_to_850nm_IR.html from the response graph, once you go above 850nm the sensitivity starts falling off really fast. that means, you would need a lot more power at 940nm to achieve the same amount of visual illumination from a gen3 nvd, compared to that at 850nm or lower. so, if you really want to go "covert", with little if any led glow, you'll want to put a bandpass filter on a 850nm led, or get a 940nm at, maybe 4-10x the power, to get the same 'visual brightness'. That's awesome. Even a troglodyte such as myself can understand pichers.
I've got some old SF Nitrolon assemblies that were never converted to LED that would make good donors for this. I'm going to scrounge up what I've got and do some shopping and see what I can cobble. I've got to dig my Hakko out for some other projects so might as well tackle this one at the same time. |
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