Steve’s LED Eyeglasses Flashlight For Preppers and Survivalists

Eyeglasses Flashlight

  • Low cost
  • Hands free
  • Very light weight
  • No bulb to burn out
  • No batteries to replace
  • Can be mounted on hats or headware

This is my Spyglass eyeglasses flashlight. It suits me and I find it very practical. I don’t care if it looks unusual. (You can’t be a real “techie” unless you have a Borg implant strapped to the side of your head.) Ha! Just kidding! (The back red strap keeps my glasses from slipping off, but is not part of the light.) The adapter is so light, it does not pull down the glasses frame and does not disturb my vision, even when driving. It is easily detachable, but I wear it permanently. The nylon threads would wear out if I took it on and off. It does not cause headaches like headband units. Their tiny batteries do not last long and are rather expensive to replace. Although the design required some thought, the assembly was not difficult. I believe the result was worth it. Because it is easy to make, the author does not offer it for sale. It is not available commercially. Only reasonable DIY skills and the ability to solder are required for construction.

Eyeglasses Adapter

This is a close up of the eyeglasses adapter. It is a 4-5/8 inch length of 14 gauge bare copper wire looped and soldered around a ¼ x 20 coarse nylon bolt, with two offset .062 inch male and female Molex pins at one end and one white T 1-3/4 5 mm LED at the other. In between is a current limiting resistor. To secure the nylon bolt on the glasses frame, the bolt has a slit in the middle half the length of the threads. I chose a lightweight nylon bolt rather than steel or stainless steel because weight was more critical than strength. Nylon is also easier to cut with a hacksaw. The bolt is ½ inch long. The nut is a standard ¼ x 20 coarse nylon nut. The nut, bolt and wire are available at any hardware store. The current limiting resistor is soldered to the plus side of the LED. The entire device is encased in 1/8, 3/16 and 1/4 inch heat shrunk tubing to cover, insulate and protect the internal connections. If a wider slot is needed for thicker frame glasses, a 3/8 inch nylon bolt could be used, or larger heat shirink could be slid over the glasses frame to hold the attachment and shrunk with a heat gun to secure the device. The slot in the bolt allows some adjustment for how far the LED protrudes from the glasses.

Cable for eyeglasses flashlight

This is the cable between the unit and the battery. I attached a small spring loaded clip to a coiled section near the top of the cable with a plastic tywrap. Snapping the clip onto my collar relieves the strain and the weight of the lower cord on the glasses and the Molex connectors. I added a miniature SPST switch inline for on-off operation. The black cable length is fitted to my body height, but can be lengthened or shortened. The battery is  terminated in a polarized one-way-only Molex female connector. The connector is convenient because an LED will not work if the connections are reversed,  This Molex design prevents shorting and reversed connections. Other connectors could be used if desired, but the Molex pins on the glasses end are very lightweight.

The cable is a two-conductor black zip cord of 26 or 28 gauge or similar stranded copper wire. The smaller the gauge of wire, the more flexible it is, but this requirement is not critical. Any size from 20 to 28 gauge is O.K., since the current drain is only 30-40 milliamps. With a 12 volt source, this is approximately 480 milliwatts. Both ends of the cable were sealed in heat shrink tubing for insulation and some degree of protection against rain. I have not tested the unit in a total down-pour, but it’s adequate if reasonable care is given. The switch can be any suitable design, but this one is small, offers one-hand operation, and is easily available. This particular switch was in the electrical department at Lowe’s for about three dollars. Soldering the switch into the female side of the Molex connector was not difficult. I encased two short lengths of large tywraps to each side of the switch inside the outer heat shrink tubing to prevent excessive flexing near the switch area. The clip and the tywraps are readily available at sporting goods, hardware or recreational department stores. The miniature SPST switch is positioned close to the battery so if inside a pocket or the Nite-Ize pouch the enclosure offers some protection against rain. Black wire for the cable is less conspicuous.

Power Sonic battery cropped

The battery I chose (above) is a Power Sonic Model PS-1208WL 12 volt, .8 Amp/Hr. cell, available at battery supply houses or online at Amazon. Their listing is PS-1208 12 Volt 0.8 AmpH SLA Replacement Battery with WL Terminal. Amazon’s cost is $12.60 plus $4.88 for shipping, which is reasonable.

Another source for the battery is a portable USB power bank external battery charger. Walmart and many drug stores sell these units very cheaply with varying battery capacities. They output 5 volts. Some of them have built in solar cells. If the Spyglass unit is not used excessively and can be recharged from a pocket solar cell, the battery becomes an unlimited source of power in the outdoors. With a 5 volt battery, the resistor must be reduced to approximately 12 to 14 ohms at 1/4 watt size. A different cable must be made with a male USB connector on one end, but the same Molex pin setup can be used on the other end. A switch can be added if desired. The battery can be easily recharged from a 12 volt cigarette lighter socket with a 12 volt to 5 volt adapter. The adapters are available almost anywhere.

Here is a picture of one power bank USB battery:

USB 2600 BWA 15WI 101 Li-ion mAh battery

This battery was chosen because it is low-cost, very lightweight, and widely available. It’s rated at 2200 mAh to 2600 mAh. Because the Spyglass led only drains 30-40 mAh, this battery will last a long time. Other batteries could be used, but with the penalty of added weight, size and cost. This battery fits well in a jacket pocket or in trousers.

The 12 volt Power Sonic battery comes with the female Molex connector, so I purchased a matching male Molex .062 connector and pins from a retailer. If desired, the unit could be hard wired to the battery, but I like the disconnect option. If discarding the Molex plug, be careful not to cut both wires at the same time and short the battery.

With the 180 ohm resistor I used, the Power Sonic cell is good for about 18 hours of continuous duty. A larger battery would give more burn time, but the drawback is added weight. This one is a gel-cell unit, so it cannot spill liquid, and weighs only one pound. It has the advantage of being small enough to fit in a jacket pocket, although I use the pouch if I want it strapped on my belt. Gel cell batteries eventually die because an insulative coating forms between the internal plates and the electrolyte, which is a toothpaste-like goo referred to as “gel.” However, gel cell batteries with low power applications like this will last for years. A bonus of this design is that it is 12 volt, so with the proper connections, any 12 volt source will recharge it. Any automobile cigarette lighter source, suitably wired, is adequate. Thus no money is wasted buying batteries. Because the battery drain is so low, the LED light output remains very constant and at full intensity for a very long time. I have never noticed a reduction in light output with this unit, which is nice, compared to most incandescent bulbs that emit a rather undesirable yellow light when alkaline batteries start to weaken.

Because it is classified as a lead-acid battery, do not ever short the terminals. Any shorted lead acid battery will give a high rate of discharge, cause a fire or even explode. Thankfully, if the LED shorts, it just makes a “pop” noise and burns itself out instantly without danger. If the 28 gauge wire shorts, it is of such small diameter that it usually burns up quickly without harm to the battery. That is another reason for using small gauge wire. The entire unit, including the battery, costs about $25. USD. to make.

A smaller nine-volt battery could be used, but the ohms of the resistor would have to be reduced to perhaps 130 to 150 ohms. Some experimentation and an amp meter would be necessary. Pushing the LED over 40 milliamps shortens its life drastically. Nine volt batteries lose their voltage rather rapidly, so they are not as good a choice as the Power Sonic or the USB battery.

Nite Ize pouch

A Pock-Its carrying pouch, (above) made by Nite-Ize, was selected to house the battery. It is very durable nylon and looks good when worn on a belt. The Power Sonic battery fits inside without pinching, and is easily removed. The Molex pins do not detach when the unit is used. The pouch can be used inside a jacket without undue bulkiness or discomfort. If desired, the cable can be neatly folded to insert inside the pouch against the battery.

Schematic for eyeglasses flashlight

The LED is the all-important factor, but today’s technology offers many choices. LED design has advanced a lot since the days when an LED was only bright enough to be the caps lock indicator on a keyboard. One source for inexpensive LED’s is http://www.goldmine-elec-products.com/products.asp?dept=1091. The author likes the Goldmine Item Number: G17802. It’s viewing angle is a little narrow at 20 degrees, but the intensity is enormous at 50,000+ and it only draws 20 milliamps. An alternate is the Goldmine Item Number: G19774. It is not as bright, but the viewing angle is 120 degrees. Ten millimeter LED’s may be brighter, but their size attracts more attention and they are heavier than 5 mm devices.

Green LED’s are now the brightest, but may be slightly undesirable, and draw more power. Red is second in intensity, but white is not bad. If white is selected, the intensity for this unit should be somewhere above 18  candela, or 18,000 millicandela at 20 degrees, (1.7 lumens) and 60 candela, or 60,000 millicandela at 30 degrees (12.8 lumens.) If brighter LED’s are chosen, they will draw additional power. The brighter LED’s have more distance, but less angle of dispersion. When walking with this unit, the width of the beam is as important as the brightness, especially when moving over gravel, snow or uphill ground. The extreme whiteness of the LED works great on snow covered terrain. LED stands for light-emitting-diode, which is how the device works.

How LED’s Work

When an applied voltage of forward bias polarity is pushed against the junction of an LED, electrons jump over the depletion region in the center and exit out the other side. As they do, photons of light are forced out of the junction. The more electrons that pass through the junction, the more photons jump out. Designing LEDs is very complex, but they are now used in everything from the Shuttle to dental surgery. Because they are manufactured in the millions, the price has dropped drastically. The 18 candella unit in his device cost $1.75 at an electronic show. More powerful LEDs may cost $3.00 each.

The author chose this LED because the current drain with a 180 ohm dropping resistor is a low 30-40 milliamps. When walking, this LED projects an area of light approximately 28 inches in diameter, and will last for about 18 hours. Do not use a dropping resistor below 180 ohms or this LED will burn out with 12 volts applied. A dropping resistor does waste some battery power. However, for simplicity, cost, weight, space and heat considerations, a plain resistor seemed a better choice than a voltage regulator. This LED projects a good distance with this resistance. For higher power LED’s, 220 ohms might be necessary.

To prevent glare from affecting the eyes when in use, the author placed a sleeve of black heat shrink tubing over the LED extending just beyond its edge, and then sealed the rear of the sleeve with a quick application of heat. The forward end of the sleeve was shrunk over a drill bit chosen to be just a bit larger than the LED body. This serves as a funnel, blocking irritating sideways emitting light and projects the beam forward, increasing the range of the device. Merely a turn of the head points the light in the direction of sight. It is very easy to get used to using this device.

This unit could be attached to a hat or a ball cap if one does not wear glasses.

Mag-Light and other manufacturers now sell LED bulbs that replace standard PR base incandescent lamps in flashlights. But they are considerably larger than one naked LED. They also pull more battery power, and are usually encased in metal, adding excessive weight.

There are also multi-LED bulbs. If more light is desired, two plain LED’s could be heat-shrinked together. While the weight of a second LED is not great, the current drain will double. A single T-1-3/4 5mm LED is tiny, and does not attract much attention. It is also an excellent illumination device when walking at night in traffic.

As a survival light, for extreme security or covert operation, this unit “shines.” With a small solar cell to recharge the battery, it is ideal for a bug-out-bag. The unit also works hands-free. The author reads with it at night, and it lights up a keyboard for typing in a dark room very well without disturbing anyone else or having to energize a room light.

Another feature of LEDs is their efficient use of battery power. It may not be obvious, but any incandescent bulb only converts two percent of its energy into light. The rest is wasted as heat. An LED sends 98 percent of its power into photons of light, and only wastes two percent. There is no filament to burn out, and the life of an LED is perhaps 100,000 hours. An LED is plastic. There is no glass to break.

For maximum visibility from a distance in emergency situations, a red LED is superior to any other form of light. LED light is not incandescent light, fluorescent, or even like the rays of the sun. Its photons are all one wavelength, not a mixture like sunlight. This one-wavelength-light is called coherent light. An optometrist once told the author the human retina is more sensitive to red coherent light than any other kind. The human eye can perceive red light in darkness better than any other color. This makes red LED flashers the best choice for distress beacons. Red LED’s will not destroy night vision. The U.S. Navy still uses red lights on ships for some occasions.

In WWII, there was an unwritten standard of excellence for naval lookouts on bridge watch at sea. If you could see a lighted cigarette at ten miles with a standard set of binoculars, you were considered a good lookout. In the 1950s, the Air Force tested their air patrols with different kinds of lights and the results were decisive. Red is the most visible color at night.

Perhaps, in His infinite wisdom, God chose red as the color for blood. Any policeman on a murder investigation, finding a tiny smear of blood at a crime scene, will become suspicious. Red seems to be the color that alerts and arouses humans. Whether it is street lights, which are now LEDs, stop lights on cars, (also LEDs,) warning lights on instrument panels, machinery, fire alarms, fire trucks, ambulances, nail polish or lipstick, red always seems to be the choice of color. Fishing boats, merchant ships, and men-of-war: every Navy in the world long ago adopted red-to-port, and green-to-starboard running lights.

Sadly, the current international SOLACE standards for emergency beacons, the U.S. Navy and the Coast Guard now use white strobe flashers. Like a camera flash, they temporarily blind the eyes and may cause deadly vertigo, or intense dizziness. The popular AA battery Firefly strobes cannot be seen at one mile, have very short battery life, and waste much of their battery life emitting light in the invisible ultraviolet and infrared regions. Although extremely intense at close range, the rise and fall spiked waveform of a strobe is very brief. The viewing time of this pinnacle is so short it isn’t surprising that they are not visible at even modest distances, especially in fog or precipitation. Strobes are used as aircraft marker lights and for police, fire, and emergency tow truck applications. In particular, blue police flashers are very irritating to oncoming traffic.

A bit of history concerning LEDs

One of the worst disasters in maritime history besides the Titanic and the Yamato occurred in 1994 on the Estonia, a cruise ship that sank in a heavy storm in the Baltic when her front doors were ripped off by a monster wave. Over 980 people were on board. The white regulation SOLACE emergency beacons on the ship’s life rafts had filament bulbs and a one-hour burn time. By the time RAF and Russian search planes arrived overhead, the beacons’ batteries had expired. All night long, the planes searched the waves, but crushing seas flipped the rafts, and hypothermia did its worst. Not until the sun came up were 126 found barely alive.

The author relates this story because he invented a red LED beacon that operates for 120 hours, will not sink like strobe units, does not irritate the eyes, and is visible at six miles or 30,000 feet. In 1993, he presented his “better beacon” to SOLACE authorities. They refused to consider red instead of white light and rejected his LED ideas. His pleas and warnings that their decision would kill people fell on deaf ears. A year later, on September 28, 1994, the Estonia sank and 854 people died. In 1991, the Andrea Gail fishing boat from Gloucester, Mass, went down in the Grand Banks. No one survived. A movie was later produced about the sinking called The Perfect Storm. One hundred sixty-five fishermen perished at sea along the East Coast from 2000-2009. On October 1, 2015, the El Faro was lost with 33 on board. The carnage continues every year. The author lives with the memories.

While on a trip in Texas, the author visited the Houston Space Center, and happened to have one of his LED beacons with him. Somehow he became engaged with a NASA engineer, who had just finished a Shuttle lecture to a crowd of tourists. At the time, NASA was very concerned that if for some reason, all the radios on the Shuttle went dead, the ground stations would lose communication with the astronauts and visa versa. The author showed the engineer his beacon and told him it was visible at a minimum of six miles. This startled the engineer. He gave the author his NASA card with an address. He told the author to mail one of his LED beacons to a laboratory in Maryland, where the beacon could be tested for visibility. The author sent the beacon. After a couple of weeks, the author received a call from the director of the facility. If the sky was clear, and if the Shuttle was in orbit at its usual azimuth, the author’s red LED beacon could be viewed on Earth from the Shuttle. The beacon could be used for emergency communications in space. Not bad for a piece of plastic the size of a pencil eraser!

Pix of eyeglasses flashlight in darkness

This is a picture (above) of my Spyglass’s LED pattern in total darkness, about five feet from the ground. The emitted beam clearly illuminates the walking area in front of the user. The effective horizontal range is about 75 feet, depending on the background. Many high-power flashlights are powered by only one LED, just like mine. Seeing is believing! The end.


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