The Light-Emitting Diode (LED) can be an excellent light source for woodworking and crafts projects. With only a little effort you can add light to your projects. Here's how:
This construction note covers:
There is no end to what you can do with LED's to light your craft projects.
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As odd as this may seem, we wrote up this construction note to support of making 3D wooden blocks of sites for settlements on the Moon. If you are interested in human space exploration then please check out our big lunar project, The Big Moon Dig.
Return to the Moon with us now to prepare the ground for a real lunar settlement through study, simulations, team building, and exploration. We can do this.
You might find our new approach easier to understand if you read our science fiction short story: "The Big Moon Dig".
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This design includes two detailed sketch sheets and an Excel spreadsheet that are critical to you successfully building this circuit. You can get them at: order the sketches. Look for "LED" under freebies or simple write LED in the text box at the bottom.
Alternatively, all the sketches are included in the text below and you can download the spread sheet directly from the Web, LEDSpec.xlsx.
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These LED circuits are designed so that they could be build by an amateur woodworker of moderate skill with a modest home shop and a few tools specifically for working electronic devices. Their construction require work with simple electronic tools like a soldering iron, multi-meter, and long-nose pliers.
The major construction challenges relate to:
This build requires working with 110 volt AC power supplies. It is best to simply use commercial electronic power supplies so that you are never exposed to the line voltage. Once past the power supply you will be working with voltages below 48 volts.
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A good discussion of the history and technology of LED's can be found at Wikipedia, Light-emitting diode.
The key points you need to know are:
A LED has only two key parameters: (1) diode voltage, and (2) maximum current. These are usually given in the specification but may be obtained by simple testing.
The LED diode voltage is a result of its internal design and will be different for each color and intensity rating. Typically this voltage ranges from 1.6 to 4.0 volts.
The more current you put through the LED the brighter the light output, up to a point. Excessive current can fuse the internal parts or kill the diode's light output by heating. The current limiting resistor is therefore a critical part in the circuit. Lower currents also extend the lifetime of the LED.
A basic LED circuit (shown above) has only three parts (1) a power supply, (2) a current limiting resistor, (3) the LED.
The power supply must be direct current(DC)and with a voltage above the sum of all the diode voltages that you wish to run in series. For safety the power supply should be isolated from the input power lines and be of low voltage (below 50 volts).
The value of the current limiting resistor is calculated in the accompanying spread sheet. The normal range is from a few hundred to a few thousands ohms. The power rating can be low but the resistor needs to be physically large enough to work with by hand.
The LED will have the positive lead marked by being long or perhaps a flat side on the base. If in doubt, simply use the test circuit. It does no harm to hook the LED up backwards at low voltage with a proper current limiting resistor in place. You simply get no light.
LED's can be bought from a number of sources in a bewildering array of colors, sizes, and intensities. Devices for this project were obtained from the following sources:
You might consider buying an assortment of LED's to help you work out exactly what you need. Also do not forget that you will need a good soldering iron and some very fine wire. Also look for the mating connector for your power supply.
After you download the sketches, these notes will help you understand them.
The accompanying sketch has to basic circuits and the steps for making a Lantern.
The first circuit shows the simple test set up. Note that it uses a battery and has a current limiting resistor.
The second circuit shows six LED's wired in series. Note that all the plus leads are in the same direction and that there is only one current limiting resistor.
The bottom sketch shows the steps in turning a 3mm LED into a model lantern. This example is described in detail below.
The second page provides a sketch of a miniature rope making machine.
The LED Spread Sheet is outlined in four parts (1) Power Supplies, (2) LED Specs, (3) Individual LED, and (4) Series LED's.
The power supply section gives the output voltage and current rating. We recommend that you use a modular power supply, probably one from your old electronic equipment. Laptop power supplies are particularly good and cheap. These provide isolation from the lines and low voltage for safety.
The LED specifications are the diode forward voltage and the maximum rated current. This can be taken from the catalog or packaging of the LED, but often have to be taken by testing (see below).
The Individual LED Section calculates the value for the current limiting resistor given a specific single LED and a specific power supply.
The Strings Section calculates the value of the current limiting resistor given a number of specific LED's and a specific power supply. It is assumed that all the LED's in a series will be the same type.
The picture of at the top of this article is of a wooden model of the Clipper Ship Flying Cloud that I build back in the 1970's. It has the special features:
Because it uses an insolated low-voltage power supply, the power can safely be transmitted to the ship through the mounting screws and to the top through the four metal posts so no external cables show.
Many woodworking projects will benefit from individual points of light. The example give here in detail is a lantern for a model sailing ship. The same circuit can also be used for the running lights, the binnacle, and cabin lighting.
The LED used for this model lantern is a 3 mm in yellow. You may choose either a clear or yellow lens.
You want a power supply that (1) has a DC output between 5 and 48 volts, (2) can provide a few hundred milliamps, (3) is sealed, and (4) provides isolation from the power mains. These are very common now days and you may even have several left over from old electronics. I particularly like the ones for laptops.
It also helps if the power supply has a shape that can be build into the base of your project so it does not show.
When you order electronic parts try to find a receptacle for the dc power cable plug of your power supply. This can be tricky.
The current need by a LED is very low and you already are placing resistance in the line. This means you can use very fine wires. In fact you can use as fine a wire as you can physically work and solder.
Fine magnet wire, gage 28 to 32, comes with an enamel insulated coating that is good enough to allow you to twist two wires together if you use low voltage as here. You can also scrape off the insulation with an Exto-Knife and tin the wires for soldering. This takes great care for small wires.
Simply twisting two fine wires together doesn't look very much like a rope for a model ship. You can make a miniature rope with two wires and a piece of cotton thread using a simple rope machine (see above). (Please e-mail us if you would like a more detailed explanation, Woodware@woodwaredesigns.com.)
The sketch above shows the steps in turning a 3 mm LED model lantern for model projects.
You can make variations of this design for all sorts of lighted bits in models. You can also use series LED for internal lighting for buildings.
You can make a simple tester for LED with an old 9 volt battery, a 1K resistor, and a few alligator leads (see circuit above). Be careful to never attach a LED to the battery without a current limiting resistor.
Be sure to mark the positive lead.
Use the spread sheet to choose the value of current limiting resistor you need. The value will depend on both your choice of LED and power supply.
Resistors are only available in certain odd values. Use the available value just a little higher than what you calculated.
If you know the maximum current for a LED, do not exceed that current.
You can try a few different slightly larger resistor values to get an idea of the amount of light to expect. This is best done in a dark room.
In models are only needed as far as they will show. As soon as you can, route the wires inside your model. You can then protect them with tubing or connect in larger wires. The resistors are often place on a piece of general purpose circuit board and hidden in a building or cabin. The power supply can be hidden in the base.
You can now buy whole strings of LED Christmas tree light at a cheap price. I paid $20.00 for a string with 100 LED's in a warm white. This is a good source of matching LED's too, for example, to light the edge of a glass or acrylic shelf.
What you get is (1) four strings of about 25 matched LED's, (2) a truly lousy power supply, and (3) a controller that produces more comic effects than useful ones.
Also note that each of the four strings has one current limiting resistor build into the first LED base. This makes these four LED's special.
You could use it as is by concealing the unusable parts inside you project. I think this is a bad idea due to the extreme poor quality of the power supply.
Or,
You could try to unravel the four strings and use them separately, but the solder connections are fragile and you will probably damages several of the joints.
Or,
You can cut it to pieces and use the LED's in shorter series with a better power supply and add wire lengths to suit your project. This is the approach I recommend.
You can cut the strings into the individual LED's with leads about 6 inches long. Be careful as the wires at the connections are not very strong. Find the four LED's with resistors build into the base and set them aside.
You can reinforce the weak bases with a match head dot of glue down inside the heat shrink base. Hot glue works well but you have to be careful with the hot tip of the gun. Epoxy works well but is a nuisance to apply. Model makers glue will work.
Do not use silicon materials as they are catalyzed with acid and will corrode electronics.
You can now try as many as you need of the LED's in our battery tester. Note the diode voltage and current. Mark the positive lead with a piece of tape.
Use the spread sheet to determine the umber of LED in series that work for you power supply. In the example, a 19 volt laptop power supply would take six LED's in a string. It could handle dozens of these strings in parallel.
Use the spread sheet to size the current limiting resistor. You will need one resistor for each string.
Please contact us at Woodware@woodwaredesigns.com if you would like more information on:
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If you send us a picture of your finished project, we would be happy to put it on our web page. We need pictures of projects with real people standing beside them.
Don't forget to order the sketches.
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