This is one of the newest applications found for the still-new deep violet LEDs just coming on the market.
This tiny keychain light is being sold for its ability to cause a UV-like fluorescence in a variety of materials such as postage stamps, credit cards, and paper money.
The LED in this flashlight is a new deep violet model emitting at between 390 and 395nm which is right at the border between violet and ultraviolet. Until recently, this LED was only
a laboratory curiosity, and before that (late 1990s), only a myth, like the Loch Ness Monster or Bigfoot.
The light comes ready to use right out of the package.
To turn it on, give it a gentle squeeze; quit squeezing to shut it off.
The main use for a light like this is to check official documents for forgery. The paper money in many countries has anti-counterfeiting measures built into it that will glow
when this light is used on it. In US money, it is a stripe embedded in the bills.
Some postage stamps also have similar technology; see the pictures below for an example of this found on Hong Kong postage.
It has also been said that some types of credit cards have a hidden picture on them which will become visible under the light from this flashlight; however since I've never
had a credit card, I am not equipped to test or verify this.
This light uses unusual CR1616 lithium coin cells. Hopefully, you'll be able to find these at your local pharmacy or a known battery source like Radio Shack.
To change them, flip the light over and remove the three Phillips screws using a #0 1.6mm or 2.0mm Phillips (a whole kit of them can be bought at Radio Shack for about five bucks).
Then carefully pry the halves of the light apart; lifting straight up so you don't break the pins.
Carefully remove the expired batteries and ruthlessly flush them down the can. Nawww, that's bad for your sceptic tank... better just trash them instead.
But look carefully! There's a square piece of tape on the top battery. So go to your scotch tape dispenser, and dispense a piece of the same size, and apply it to the negative (button) end
of one of the new batteries so it looks exactly like the old. Now you can finish throwing the old batteries away.
Lay the untaped battery, button end facing up, in the bottom half of the flashlight, and then set the other battery on top so the section with the tape overhanging goes under the LED
lead towards the front of the flashlight. Then press the case halves back together and screw in the screws.
The tape is there to prevent the top battery from shorting out against the LED lead, so you have to put it on. Scotch tape, masking tape, or electrical tape should do the job.
This is one of the most asinine battery changing procedures I've come across, and I really hope they figure out how to make these lights work without tape. :-O
I can't say this is the best light I've ever used. It seems to be alright, except for having to have tape on the battery.
The screw holes seem inadequate, and already show signs of stripping, so you'll need to be really careful when you reinstall the screws that you don't crossthread them and don't
overtighten them either. But then again, what do you expect for eight bucks, when the LED and batteries alone are easily worth that much.
The light is not water resistant, so a concerted effort should be made to keep it from falling in the toilet or drowing under your lawn sprinkler. If water does get in, just open it up and
dry out all the parts, and it should be fine.
What makes this light worth having though is that LED. Nobody else is making a flashlight or other portable source with a 390/395nm near-UV LED.
If this light has a saving grace, this is definitely it.
The LED used in this light causes fluorescence (glowing) in a number of different materials. Brightly colored plastic, some types of markings or bar codes left on mail by the
post office, orange traffic cones, brightly colored price stickers, and "blacklight" posters are some of the things that will glow brightly.
The light also makes old sweat and urine glow, so it can be used to check garments or bedsheets for evidence of armpit puddles and urination; however
this only works if the fabric itself does not also glow. It can be used on some carpets & rugs to check for dog pee, so you can clean & deodorize that spot so Fido will be less likely
to "re-offend" in the same place.
The use for which this light is marketed however, is to check paper money and other official documents for counterfeiting. Newer US money has a strip embedded in it which
usually glows under longwave UV. I say "usually" because sometimes this glow is lost if the bill goes through the washing machine once or twice. The strip can still be viewed
using a pass-through detection method though.
Other official documents are sometimes treated with UV sensitive materials. Some postage stamps have glow strips that show up
under this flashlight, and some business checks (and a few personal type checks) have fibers that light up a brilliant greenish white in this flashlight's deep purple light. Tickets
for official events like baseball and football games often have a pattern on the back that only becomes visible when you shine a light like this at them.
Try shining it at your TV set or computer monitor (when they are off) and see if you notice a greenish white glow on the screen.
Try it on glow-in-the-dark watch or clock hands.
Try it on different kinds of white paper. Some kinds glow bright sky blue, others just show a dull purple.
Shine it on the leaves of different houseplants. Most will show a dull red color.
Greenish colored antifreeze fluid should glow brightly under this flashlight (not tested, as I don't have a car)
Some compact fluorescent light bulbs will glow a funny reddish salmon color with this light.
Shine it on your water closet and the immediate area around it. Prepare to get out your mop, bucket, and bottles of Lysol, especially if you have small boys in the house.
See how well they *really* clean around those wall-mounted urinators in public restrooms. Yuck!!
Some clothing like white underwear and T-shirts will glow brightly under this light.
Shine it at shirts hanging on the racks in a thrift store. Sometimes, otherwise invisible stains will show up as big glowing white patches under the arms with this light - don't buy *that* shirt.
Older stains tend to glow more brightly than something made recently for some reason.
Similarly, you just might find "the invisible enemy" in department stores too, if a garment has been worn, sweated through, and then returned with a lie; although your chances of it aren't very high because they catch
most of them before hitting the sales rack.
Some species of scorpions indigenous to the southwestern US will glow a whitish green.
Some types of mushrooms, toadstools, mould and other fungi may also glow under this light. I found some in the soil of a potted plant that was not visible in ordinary light.
Just experiment... you'll find a lot of stuff that glows all funny, and maybe find something quite unexpected.
Invisible bar code marker left on a Christmas card that went through the mail.
Left: Without UV flashlight illumination.
Right: WITH UV flashlight illumination.
Deep purple, wide-angle beam from approx. 1 foot away
The camera renders the deep purple glow as a blue color; in reality it looks like dark royal purple.
May be too short in wavelength to be analyzed further with the equipment at my disposal.
Test unit was received on 12-27-01, and is in the queue for being tested, bashed and thrashed.
I have somewhat of a backlog here, but I'm trying to fit everything in a bit at a time so nobody gets left out for too long.
The LED used in this light is the shortest wavelength I've seen in this type of LED; and appears to be between 388nm and 392nm.
I'll also be experimenting to see if there's a way to form the LED leads and eliminate the need for tape on the battery.
CAUTION: The light emitted by this product is right on the border between visible and UV, and there will be smaller levels of radiation that clearly falls into the long UVA range.
Therefore, you should not shine this light directly into your eyes for any amount of time beyond a single blast of 1 or 2 seconds on any given day.
Although not as likely as it might be with a shorter wave source like the Nichia LED or mercury vapor suntan lamps, it is still possible to damage your eyes with prolonged
viewing of the direct beam (putting the flashlight up to your eye and letting it cook there). Signs of UV exposure include a burning or "sand in the eyes" sensation, and
a hazy look around light bulbs or other light sources. Symptoms of UVA exposure may take
an hour or two to develop following exposure. Mild cases are typically self-correcting within 24-36 hours; if you have anything more than mild symptoms, call your eye doctor
right away, and bring the light with you so he will know what he's dealing with. Tell him the "peak wavelength" is right around 390 nanometers, and let that be a lesson learned.
Small size hides well in purses, bags, etc.
UV LED wavelength is shorter than usual
Uses batteries that could be expensive or difficult to find in an emergency
User must tape one of the batteries during battery change
Not very water resistant
MANUFACTURER: Wilycon LTD
PRODUCT TYPE: Miniature keychain light
LAMP TYPE: LED, Deep violet, 5mm
No. OF LAMPS: 1
BEAM TYPE: Wide angle with central ring artifact
SWITCH TYPE: Momentary, squeeze on/off
BATTERY: 2 CR1616 lithium coin cells
CURRENT CONSUMPTION: Not yet measured
WATER RESISTANT: No
ACCESSORIES: Batteries, spring clip keychain attachment
WARRANTY: Not stated
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