20 Infrared LEDs Light Up Nothing

Try placing them closer together. Maybe in a circular pattern. Add a reflector.......................like a flashlight reflector, and you should be able to get a beam of light.

All LED bulbs are not created equal either. Some are brighter than others.

http://www.superbrightleds.com/cgi-bin/store/index.cgi?action=DispPage&Page2Disp=%2Fcompcool_warm.htm

Are you looking at it with an infrared camera or viewer? Of course your eyes won't see much from infrared LEDs! Is the apparent "light" shining from the LEDs in your photo a reflection from your camera flash, or do they actually emit a little light in the visible spectrum?

Well now, if it can illuminate a field 1" away then it is illuminating things farther. Just not illuminating things sufficiently bright for your system. Now you might have a camera lens or CCD filter that blocks infrared light. You may not be providing enough current through your LED even though the voltage drop reads correctly. Many commercial LED lamps pulse the LED at very high currents for a CCD is an integrating detector and will perceive a quick pulse as continuous light. You may even just be using the wrong type of LED for your purpose.

Without some better clarification, I cannot help.

Since infrared is not visible to the naked eye it probably isn't visible to your camera either.

First, check the specifications for the LEDs for their peak emission wavelength.

Second, check the specifications for your camera and lens.

Chances are you will find that the camera is not sensitive enough at the required wavelength.

The LEDs will emit at frequencies outside the peak, but at much lower amplitude. Your camera probably works at these off-peak wavelengths and you are seeing the residual light.

+1 point on the IR film filter on the CCD.

-1 point on the LED. How can you have a potential of 1.5 VDC across the diode (assuming polarity is correct and it is a working diode) and not have current?

it's connected backwards?

I didn't say no current, I said they might not get enough current. A current-limiting power supply can supply enough voltage to give each LED an average of 1.4V, but with only a trickle of current which would not be enough to provide the rated 'luminous' output. (Luminous is in quotes since the output is not visible, and the term does not exactly apply; it would be watts of photon energy.)

LEDs are typically dimmed via pulse width modulation at a fixed DC voltage with the dimming done by decreasing the effective current.

I see your pointy. However, post # 8 lists the rated spec as Max Voltage Vf:1.5V.

If the LED is functional and polarity is correct, 1.5 VDC will produce the correct current.

Typical forward voltages at operating current are higher than 1.4 or 1.5 volts for LEDs.

Many digital cameras can "see" infrared. My Nikon D40X can, and I think many other Nikon cameras can. I don't know about other brands. The problem is that a very dark red filter is needed to block visible light in order to get an image in I-R. I generally use 2-3 sec exposures. The LED's may not be bright enough.

GA

We use Joo Janta 200 Super-Chromatic Peril Sensitive Sunglasses.

I understand now. The light form these led's is what the camera is seeing. I just broke my ps2 eye toy while trying to remove the infrared filter from it. The camera must have an infrared filter in it.

No way the leds in photo are 1.5V max. Make a 10mA current sourse and test one of them. Measure the voltage accros it's legs. I bet it's no less than 2.6V . If yes the data you have on leds are wrong. S.M.

I just bought them off eBay from Elektor Base and in the description it states that their maximum voltage is 1.5 v. In complete darkness they glow dull red.

Description

• LED 5MM ROUND INF RED 940NM
• LED Type:Standard
• LED / Lamp Size:5mm / T-1 3/4
• LED Colour:Red
• Dominant Wavelength:940nm
• Viewing Angle:10°
• Max Voltage Vf:1.5V
• Forward Current:50mA
• Lens Shape:Round
• Mounting Type:Through Hole
• Opto Case Style:Through Hole
• No. of Pins:2
• Lens Type:Water Clear
• Material:A1GalnP/Si
• Operating Temperature Range:-25°C to +85°C
• Typ Voltage Vf:1.25V

Ooops! 940nm is much more effectively cut from IR filters. The common wave length for night vision camera LEDs is 840nm. This detail can make a BIG difference in what your camera can see. The 940nm also justifies the low voltage. S.M.

The LEDs are outside the visible range, so you will not detect any irradiation when powered.

You need a camera, such as a IR security camera, to "see" them at work.

These diodes are used almost exclusively for security camera lighting. 940 nm is the same wavelength used by night vision cameras. [p[] I would also not look into these diodes. I don't know if they are a problem, but you have a fairly large bank of them.

Even if you cannot see the wavelength, it can damage your eyes. Until you know the output, keep your eyes safe (they are tough to replace).

You could try looking at them with your cell phone camera, I have used mine to test a infared remote control to see if it was lighting up.

~A~

So even if I can not see the infrared light, it could still harm my eyes?

Yes, high intensity light even spectrums outside our range can damage our retinas.

~A~

Actually, because your retina does not perceive this light, causing a blink, squint or iris constriction you run a greater risk of eye damage from non-visible light than visible light. Now I'm not an ophthalmologist nor do I have any idea how well your lens will focus this light but I'd rather be safe than sorry.

I removed the infrared blocker from my flycamone and now the infrared light looks the part!

Also, i looked at the light while facing a mirror and it has no effect on my pupils. My eyes feel slightly weird but that's probably the power of suggestion.

You said the LEDs were actually getting 1.4 volts. If they were getting their full rated current (50 mA, which seems unlikely since they are not at full voltage) the power per LED is 1.4 * 0.05 Amps = 0.07 Watts per LED; x 20 LEDs = 1.4 watts, total for the array. That's actually not a lot of power. I haven't done the calculation yet, but my guess is that a 40 W incandescent light will be putting out way more IR wattage than these LEDs. So I think your eyes are reasonably safe, so long as you keep the array from close proximity to your eyeballs.

If you want, compare the brightness perceived by your camera for the LED array and for a bright flashlight or a small incandescent lamp. That would give you an idea of how much relative IR the array is emitting vs common everyday VIS-IR emitting devices.

Just to follow up my previous comment: A 40 Watt incandescent light bulb produces 40 watts of electromagnetic radiation, of which roughly 15%, or 6 Watts, is in the form of light. The rest, 34 Watts, in almost entirely invisible infrared radiation.

Your LED array produces 1.4 Watts of electromagnetic radiation, of which almost 100% is invisible infrared radiation. (The red glow you see is the tiny portion emitted in the visible spectrum.)

So clearly, the 34 W from a 40 Watt light bulb produces about 24 times the amount of IR that your LED array produces. The key difference is the light bulb radiates over an entire sphere, whereas your LED radiates into a 20 degree cone (assuming the data you quoted was for the half-angle of the emission cone, which is what is usually given). [Perhaps a better direct comparison to your LED array would be an incandescent spot light, where the light is beamed into a narrow cone.]

Since most people have looked at 40 W light bulbs without incurring long-term eye damage, I'd say it's not likely you'd damage your eye permanently by occasionally looking directly at your LED array, unless you deliberately held it up near your eye and stared into it.

The incandescent bulb IR output is spread out over a much, much broader spectrum versus a 940 nm IR diode, which has a narrow pass band of emission.

There are two good reasons not to look directly into the LED array:

1. It is unclear if it is safe.

2. The emission is invisible to the eye, so what is the point?

If you insist on looking at the IR diodes, do it with the power off because you will see the same thing.

Yes, I modeled the LED as fairly narrow here (in my spectral analysis program) though I used and tested them a few years ago, and I know the spectrum is a bit wider than this. Nevertheless, this gives a pretty good representation of the LED spectrum vs the incandescent bulb. The peak intensity of the LED is greater than the bulb's at 940 nm, but this would only be a concern if there were a structure in the eye sensitive to this particular wavelength. The broad spectrum of the bulb includes a lot of true infrared 'heat' energy which actually might be more damaging than the IR light' at 940.

And to re-iterate -- I'm not suggesting anyone stare into an array of IR LEDs, I'm just saying that brief inadvertent exposure probably is nothing to worry much about.

Nice job!

I agree, but why take the chance, as our OP appears to have done!! It may even be a good idea to get some eye protection at the frequency of the LEDs you are working with.....

That was not a good test, totally unsafe. You were given good infos about possible eye damage.

Remember that some sight tests of bright objects only allow 2 tests per person max....

LEDs are improving almost daily and they are well into powers that can damage human eyes......

It reminds me of the old saying "Fools go where Angels fear to tread!". I cannot imagine why?

Thanks for all the help and comments. I just need to buy a new eye toy now.

It's cool to come to a thread like this late in the game and see it already answered. Nice job to everyone on this thread.

Just a note on led power. LEDs are much more efficient than incandescent bulbs, so 6 watt LED array =~ 60 incandescent bulb. Where does the extra power in the incandescent go? A lot goes to heat. Just keep that in mind, 1.4 Watts, if that calculation was correct, isn't bad at all.

Most digital cameras I've come across will show whether an IR LED is emitting.

Usually (oddly enough) it shows up as bright blue. Don't need to take a photo - you can see it on the camera LCD viewfinder. Try it with your TV remote (assuming it's IrDA) to test the principle.