Backwoods Home Magazine #127 - Jan/Feb 2011

Anarchy Radio 05 15 2018

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This could include portable lanterns for camping and emergencies, trouble lights for use on car power, portable spotlights or floodlights with handy mounting attachments that could be run from a small rechargeable battery, and various fixtures for use in a camper, cabin, or home. With the changing nature of the technology, pages filled with details about specific LEDs and products could quickly become useless. But it is also necessary to use real-life examples in order to talk sensibly. The most straightforward source of components is a retail supplier, such as LEDSupply www.

This company supplied components for the example projects pictured here and they receive very positive reviews for service. Of course, there are other good vendors, too. There are also bargain components available from discount outlets and websites like eBay. You can get some good deals, but there is a huge range of quality and customer service may be difficult or impossible. Remember that, especially in a cabin or home, even low voltage electronic components could pose a fire hazard if they fail.

There are several different categories of LEDs see Part One and any of these could be considered, depending on the amount of light you need and the availability of suitable drivers.

Here, we will stick with single-die LEDs because they are relatively easy to configure and because drivers are readily available. In addition, single-die LEDs have at least a couple of general advantages. First, for area lighting, several single-die LEDs can often be the better choice because they allow both the light and the heat to be spread out over a larger area. Second, continued improvements in efficiency are likely to turn up first in the single-die category.

But neutral and warm white color tints have now been released. Cool white is readily available and, by the time this article gets to print, it is likely that the same will be true of the more pleasant color tints.

Because this LED represents the best efficiency available at this moment, we will use it for our examples. Regardless of what type of LED you select, there are a couple essential numbers that are needed. One is the maximum current that it will handle, which is usually provided in milliamps mA. Good mounting and connections can be a real challenge when trying to use tiny, bare LEDs.

In contrast, a star board is easy to solder and it allows for simple mechanical mounting. In most cases, you can simply secure it to the heat sink with a heat-conducting epoxy or with a non-hardening heat transfer paste and some small self-tapping screws. Vendors that sell LEDs can also supply these materials. It should be noted that there are also pre-made assemblies that can be useful for some projects.

Some of these strips even include on-board drivers, so firing them up can be as simple as mounting the strip to an appropriate heat sink, providing a power feed, and adding a suitable cover or diffuser. Note that some of these options require the unit to be electrically isolated from the metal mounting surface. Make sure to consult the technical information.

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As we saw in Part One, heat management is essential. For many applications, there are pre-made heat sinks which are readily available and fairly inexpensive. The back of the heat sink the cooling fins should be left exposed to the open air and should not be enclosed in any sort of housing. In addition, the heat sink will work best if it is mounted with the fins pointed up or on its side with the fins running vertically. Within these limits, the heat sink and mounted LED can be incorporated into virtually any sort of lantern, lamp, fixture, or housing that you can brew up for your needs.

A single small heat sink about 2. If you are experimenting with your own materials, note that surface area is generally more important than mass and that a flat black surface will actually emit heat much more efficiently than a shiny one.

Most LEDs can be operated over a wide range of electrical currents and there are some huge tradeoffs. As the current is increased, more light will be produced.

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But more heat will be produced, too. In addition, there is a diminishing return: On top of this, published outputs and efficiencies the ones I will cite assume a relatively low operating temperature for the LEDs. As the LEDs are pushed to higher current levels, it becomes progressively harder to maintain a low operating temperature, even with good heat sinking. In any case where maximum efficiency is a must, lower operating currents are a necessity. To prevent thermal deterioration of the LED, they are also a good idea when a very long service life is desired. This all means that the LED will unavoidably run at a temperature that is at least somewhat higher than the surroundings, even if your heat sink is a fifty pound chunk of copper with huge fins.

As the current input is increased, this temperature elevation will also increase. If we throw in the additional fact that home-brew heat management is likely to be less than ideal, the conclusion is that modest current inputs are the best way to insure a long service life. Of course, the drawback is that more LEDs will be needed to produce a given amount of light.

But when we get to things like trouble lights, camp lanterns, and cabin lights, the situation can be somewhat different. Even at fairly high operating temperatures within reason , LED service life can still be many thousand hours before any significant reduction in brightness will occur.

In these uses, it can be perfectly acceptable to run the LEDs at full power assuming that adequate heat sinking is in place because such lights may not get a thousand hours of use even in several years of service. Efficiency will drop off, of course. But, as a practical matter, it may be both easier and cheaper to use a little bigger battery for such projects than it would be to build lights that use larger numbers of more gently-powered LEDs.

For cabin or home, the lights could be designed so that a moderate brightness setting would prove adequate for most needs. But when you need extra light for intermittent tasks like cooking or reading, it would be available by turning a knob.

Portable lanterns and work lights may get run at maximum brightness for routine use, but they could be turned down if an emergency requires you to conserve battery power. Of course, generous heat sinking should be used to allow good heat removal during highest-power operation. Electrical current measurements with a good meter can give you a handle on how much juice is being used by adjustable lights at various brightness settings.

A broad, uniform field of light is usually desirable for general area lighting and the natural pattern of the bare LED may be fine in some settings.

But if the LED is subject to possible damage, it would be prudent to cover it with a clear plastic or glass cover. If glare is a problem or an even more diffuse light is desired, a textured or frosted diffuser may be preferable. However, extreme care should be used in selecting diffusers because heavy frosting or texturing can greatly reduce the emitted light. Several different patterns are available and the right one can greatly improve the useful efficiency of your project because it will squeeze the light into the area where it is needed.

For example, an unfocused LED might make an excellent area light. But when it comes to a trouble light, you may find that a lot of the lumens will wind up landing outside of where you really need them be it a fuse box or an engine compartment. One caution with these lenses: When ordering, make sure that you are getting the correct ones. A focusing lens sits in front of the LED and it can be designed to gather the vast majority of the light output into a specified pattern with a very sharp cutoff between bright light and virtually no light.

The rest which can be a major portion of the total output will escape directly out of the front of the LED without being captured and focused. In many flashlight applications, this spill light is by no means wasted. The central beam allows you to spot things at a distance, but the spill light simultaneously allows you see closer hazards over a much wider area. In a defensive situation, this could be a menacing intruder. In more pristine environments, it could also be the tree branch hanging at forehead level or the gopher hole at your feet. But when it comes to an area lighting job i.

Here, the right focusing lens can provide much more efficient use of the light. Good commercial drivers are available for single-die LEDs. These take voltages which would otherwise be too high and reduce them so as to push a constant current flow to the LEDs. It is no larger than a piece of bubble gum and can have standard outputs of , , , or 1, milliamps mA. The driver can be mounted in a small box and the trimpot is designed to be mounted through a hole in the enclosure with the adjustment stem sticking out.

Attaching a knob to the stem will then provide easy adjustment. The standard DC version of the BuckPuck will handle up to 32 volts, so it is very suited to or volt DC batteries. One very important thing to note is that drivers like the BuckPuck can often power more than one LED. The maximum number will depend on things like the voltage supplied by the source and that required by the LEDs. There are some extra precautions that should be taken when the drivers will be connected to a battery that is simultaneously attached to a charging system. Care may be required if the driver will be mounted remotely from the LEDs or if there is a long wire run from the driver to the power source.

It should be noted that the efficiency of a given driver can vary depending on factors like the input voltage. For applications like a camp lantern or work light, this is probably a fine detail to lose sleep over. But if you are planning a more extensive project, driver efficiency can become significant.

A caution about homemade drivers: These can provide a stable current output over a wide range of voltage inputs, but the pitfall with many simple circuits is their efficiency. They often do their job by essentially dissipating some of the input power and turning it into wasted heat. Depending on factors like the input voltage of the source and the voltage required by the LED, it is possible for a simple current regulating circuit to use as much power as the LED itself, or even more!

Cree originally specified a maximum current of 1, mA, but they raised it to 1, mA after further testing. Second, simple drivers are not as readily available at higher outputs, at least as of right now. Third, for reasons mentioned earlier, higher inputs could result in a high operating temperature under typical homebrew conditions.

When it comes to powering LEDs, the first thing to address is the number of LEDs that can be connected to a single driver. To determine what is possible, we need the voltage required by the LEDs, the voltage required by the driver, and the minimum voltage that will be supplied by the power source when it is at a state of maximum discharge.

This could be supplied very comfortably from a volt lead acid battery which should never be discharged to a voltage anywhere near that low. It is important to note that a battery run down below this voltage such as during an emergency will still continue to power the LEDs, but their brightness will decline progressively as the voltage drops further. When connecting multiple LEDs in this kind of setup, they are wired in series: Of course, a proportionately larger heat sink or multiple small ones is essential when setting up multiple LEDs.

A higher voltage system can allow even more LEDs to be powered from a single driver, but there are a few cautions here. First, it is important to make sure that the maximum voltage of the power system never exceeds the voltage limit of the driver. Second, even though the driver is still delivering the same amount of current through the LED string, the total power it is handling will increase as the LED string is made longer.

As we know, higher current will give us more lumens, but with a reduced efficiency. As discussed earlier, it becomes progressively harder to maintain low operating temperatures for the LEDs as current input is increased. Thus, the spread between these ideal values and typical field performance will likely become bigger as the current input is increased. If you are visualizing what you might need for a project, it is handy to recall that a standard 60 watt incandescent light bulb will produce about lumens.

In many practical settings, operation at a compromise current somewhere between these levels can provide a good balance between output and efficiency while keeping the heat output reasonably modest. For instance, operation of the three LED string at mA would generate about lumens while retaining an efficiency of around lumens per watt.

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Increasing the current to mA would result in about lumens with efficiency in the neighborhood of lumens per watt. Remember that operation at higher current inputs will result in more heat, so it is important to plan your heat-sinking accordingly. BuckPucks are available in a choice of the current outputs just mentioned. If you are certain that you only want to run the LEDs at lower levels or mA , there is a slightly more complicated wiring arrangement that may be worth considering. Using the example of a volt system again, this means that you could power six XP-Gs at mA by purchasing only one mA driver instead of having to buy two mA drivers.

Drivers with adjustable outputs can still be used and data sheets will provide schematics for wiring strategies like this. It is easy to miss important points in the midst of all the numbers and there is one that definitely needs to be emphasized here. This technique allows for the use of few drivers when the goal is to run the LEDs at lower current anyways. But using two adjustable drivers to power the same LEDs as two separate strings of three would allow for up to 2, lumens six LEDs at 1, mA.

Practical ideas for self-reliant living

The question here is whether having access to the extra light is worth the cost of the second driver. The answer, of course, depends on your intended uses. In Part 1, we saw that neutral and warm white LEDs can provide light that many will find more pleasant, but that they also suffer from lower lumen outputs and efficiencies relative to cool white.

As with cool white, the neutral and warm tints are available in a number of bins that vary in efficiency. It can be tempting—and it is possible—to connect an appropriate string of LEDs in series and feed it directly from a given power source without the use of a driver. This approach has some serious limitations and it is very easy to burn out some expensive LEDs if it is done improperly. But there are a couple of reasons for mentioning it.

First, those who pursue this topic further are likely to run across it, so a discussion of the pros and cons is in order. Second, as we will see, the operating specs for the XP-G work out nicely for this technique, so it could actually prove useful in a few cases. This section includes recipes for a basic balm, baby ointment for rashes, powdered blush, quick and easy hand cream, facial masks and scrubs, after shave lotion, basis soap, toner, toothpaste, nail anti-fungal oil, soothing joint ointment and more. You can get this resourceful book here. You can also check out back issues of Backwoods Magazine which include resourceful information and projects for homesteading, personal independence and self-sufficiency.

Additionally you may enjoy: Dillon is a soapmaker, DIY-er and blogger whose life is controlled daily by a dachshund. You can learn more about Rebecca by checking out her bio. Books for a DIY Lifestyle — From living frugal to homemaking, organizing and decorating for the holidays I may receive compensation from links on this site. See my disclosure policy. November 25, By Rebecca D. November 25, at 6: Thank you, Rebecca, for sharing these timely and informational books!

• Anthropology - p. II (Italian Edition)
• Nietzsche: Lapolide dellesistenza (Tascabili. Biografie) (Italian Edition)
• DNA MARS (German Edition)
• Difficult Run
• Impurity
• Molly The Meerkat - Molly Learns About Honesty
• The Nanjing Massacre: Poems