The Flying Crank Ghost by Doug Ferguson orniske@aol.com http://members.aol.com/phanmech Revised 6/15/98 (NOTE: Be sure to download and view the related .jpg illustrations. They will make the text much easier to understand.) Halloween animatronics and their creators make strange bedfellows. You may even begin to share your dreams with the odd things you are in the process of creating. They can end up with personalities, perhaps even names. The specter whose mechanism I am about to describe never got a name - at least not from me - but she is definitely a character, and positively a lady, one who moves with a ghostly grace and mesmerizes onlookers with frightful charm. She floats in mid-air, wrapped in an ethereal glow, her eyes blazing red, and piercing the soul. Her arms move smoothly, each in its own natural way, while she slowly hovers, rising and falling as she gestures. Depending on the whim of her builder, she even may speak, her eyes flashing with the words. Does she sound like someone who should inhabit the confines of your beloved haunt? If so, ready your lab and prepare to conjure her forth, for she is simplicity itself, and the plans for her construction follow. The figure is actually an articulated marionette, which hangs from a motor platform that you suspend from your attraction's ceiling. She will demand some time to construct, but the rewards in guest reactions will more than repay your efforts. You will get complements if you exhibit this ghost. :-) The Materials * Acquire 7 yards of cheesecloth or similar gauzy material. (The fabric stock should be at least a yard wide.) Be sure whatever material you choose is not very heavy, or the ghost will not look ethereal, and you may run into mechanical overload problems with the animation drive system as well. * Find a Styrofoam wig form, even a discarded one. This will become the head. You will sculpt it with your fingers to give it character. * Purchase one small can each of fluorescent blue and green spray paint, and a can of flat black Krylon. If you have access to an airbrush, water base paints meeting the color requirements will do just fine. * Have a black light on hand. It need be no larger than a 12 inch tube. Enclose it in a simple directional reflector, which can be of aluminum foil. Be careful not to allow the foil to contact the electrical connections at the ends of the tube. Be sure not to use flammable materials in the reflector. It is recommended that you include some sort of shuttering device to direct the light only where it is needed. If black light spills into the spectator space, it can ruin the effect by causing clothing to fluoresce and over-light the scene. * Find a rotisserie motor, or equivalent. For those who are serious about reliability, I highly recommend a Dayton gear-motor, model 2Z806, available at an industrial electrical supply house. This model's output shaft runs at 6 R.P.M., and is perfectly suited to the effect. For those who prefer slower movement, get the 2 R.P.M. version, 2Z805. * Get square of 3/8" plywood, approximately 4' by 4'. The final size can be about 42" x 42". This will be used to mount the motor and animation assembly. You will drill a hole in the center through which the motor shaft will protrude. If you use the suggested gear-motor, you will also be drilling 4 mounting holes to secure the gearbox to the ply board. If you use a rotisserie motor, the mounting method will be up to you. Just be sure that enough of the motor's output shaft can protrude through the board to allow attachment of the crank. It is worth noting here that since the invention of this effect, the members of the Halloween-L internet mailing list have created many different versions of motor platform, all of which work well. Read the rest of the instructions, and it will become clear what the mounting platform for the motor must be capable of. You can decide for yourself the best method for your application. * You will need some flat aluminum stock, 1/8 inch thick by 1 inch wide by at least 2 feet long, available at a hardware store. You will also need a small U- bolt, small enough to encircle the motor's output shaft. It will be used to mount the aluminum stock to the shaft and form a crank. The best thing to use for this is a pipe grounding strap, which consists of a small u-bolt and a little bracket to clamp a wire. Hardware stores commonly have these, as well. (You will need only the U-bolt from the clamp, and you can save the bracket in your kit for future projects.) * Get five small, smoothly operating pulleys, and about 25-30 feet of rope, of a diameter which will fit them comfortably without snagging between the wheel and housing. Obtain some screw-in 'eye bolts' of the type for mounting in wood. These will be used for mounting the pulleys to the motor board. (If you choose to use a metal motor mount setup, purchase machine-thread eye-bolts.) Three of the pulleys will support the marionette, and the fourth and fifth will hold a counterweight to balance it, and take excess load off the motor. (Note that it is possible to build a marionette light enough to operate without the counterweight.) * You will need Nylon twine (or very small diameter rope) to secure the pulleys to the eye-bolts and hang the motor platform from the ceiling (or rafters) of your haunt. * Find some old coat hangers, which will be used to form the figure's armature beneath the head assembly. Five of them will probably do, but avoid pants hangers with paper sleeves - you will need the 'single continuous wire' variety. Avoid thin, easily bent wire. * Get some stiff paper and cut out a pair of hands with long, slender fingers (to suit your taste.) Make sure that the paper is thick enough to maintain position when you bend the fingers into a gesture. If this is a problem, you can attach thin wires to the fingers, which will help them stay bent. Of course, other sorts of hands might be used, but props such as stuffed gloves will not suit the character of the appaarition. The ghost will be very slender and airy, so consider this when deciding on material to use for the hands. * Make an expedition to Radio Shack and acquire two Light Emitting Diodes (L.E.D.'s) Ordinary ones will do in the low lighting used, and the 'high brightness' version would most likely spoil the subtlety of the effect. You will need a trim pot, preferably with a 10k ohm value. If you don't know what this is, ask the salesperson. They usually come in multiple packages, but are quite cheap. The trim pot will be used to 'ballast' the L.E.D. - that is, it will be set to prevent too much current from passing through the pair, which will be the ghost's eyes. You will also need some single strand electrical wire. If you decide to use the voice option, you will need 2 70v. speaker system audio transformers, also available from Radio Shack. These will probably cost you between 8-10 dollars each. If you are non-technical, don't panic. See below for more details on this aspect of the project. * You'll need white glue, large bottle. Elmer's will do, although 'Tacky' (available at most craft stores) is my personal favorite. * Find a small fan (optional) to make the figure's drapery move. Try it and see if it works for you. Use the slowest speed to begin with. * Main tools: Pliers, regular and needle-nose Wire cutters Scissors Soldering iron and solder Drill and bits Vise Patience, devotion, and loving care Construction The Head At this point, consider the expression your specter will wear. Will she smile, will she frown, or simply be enigmatic? Consider your attraction, and why she is in it. Is she the owner of the haunt? Is she imprisoned there by force? Is she the hostess? Think of what she might say to your guests, and be creative. She is potentially pure drama. Get the Styrofoam wig stand, and locate the position of the eyes. If the form has a flat front, use your best guess. Hollow out the eye sockets and mouth (optional) as if you were making a skull. The mouth should be an open oval, as if the figure were speaking. If the wig stand has lips, you may wish to leave them as they are, for a more 'comely' specter. Press the Styrofoam inward to form the required cavities. If the foam is of the dense variety, you may have to hollow out the eyes with a spoon or similar scoop. Don't rush, and use your creativity. You may wish to sculpt more detail into the face - jaw lines, narrow chin - whatever you may wish to imagine. If the wig stand has a large, extended base, cut it off. The neck must taper, and it will attach to a hooded drapery which becomes the 'body.' If you are a sculptor, modeling paste may be used to add features. Have fun with this step, and give the face character. Take your time. The face is the heart and soul of your specter, and makes it communicate. It is in this step that you should bring your imagination to bear, and give an individual identity to your prop. Next, cover the head with cheesecloth, or the material of your choice. I recommend that the same material be used throughout the figure. If the entire ghost is draped in the same fabric, there will be a feel of continuous texture. Make a thinned paste from the glue, and soak a square of the fabric large enough to cover the form. Cut this piece, and trial-fit it before soaking it in the glue. Apply the fabric, pressing it into the eye and mouth cavities, smoothing it around the facial features, and gathering the excess behind the head where it will not be seen. Do not leave wrinkles of cloth on the face, unless that is the effect you desire. Allow the glue to dry, then trim off the excess fabric, if necessary. The Armature You will be cutting coat hanger wire in this step. Be careful, and do not cut yourself in the process. An armature, for those who aren't familiar with the term, is the skeleton of an animatronic figure. You need to make a set of shoulders for the ghost, and they will be life-size. You may want to make the shoulder span a bit narrower than that of a living figure. Take a single coat hanger, and untwist the hanger hook so that you have one single piece of wire. (If you've ever used a coat hanger to pop a car door lock in an emergency, you know what is being described.) Bend the center of this wire into a U-shaped segment about 6 inches long. You should end up with an equal amount of wire on each side of the U. The narrow U should be inserted into the bottom of the neck of the head-form, and the wire extending outward from it will form the figure's shoulders. Glue this in place with undiluted Tacky glue. Carefully press the U-section of the hanger piece into the Styrofoam. Allow this assembly to dry completely before continuing. It should be noted that many builders have used additional methods of attachment, such as a pin through the neck, from front to back, to capture the U-shaped insert. Using a pair of pliers, bend the end of each shoulder into a round loop. Using your own arms as a model for length, cut up four more coat hanger pieces to represent the lower and upper halves of both arms. Join the arm segments at the elbows with interlocking loops like the ones at the shoulders, then similarly attach the upper arms to the shoulders below the head. Make sure that the arms can swing freely and not lock up in normal movement. The figure's hands may be cut from thick paper or cardboard, as mentioned above. You will wrap these paper hands in the same manner in which you covered the head. Attach the hands to the wrists. Small loops in the ends of the coat hanger wire make this easier, and you may use any method you like, as long as the hands are securely fastened on. Adjust the wrist positions by bending the wire appropriately. You will make final adjustments when the figure is finished and on its flying rig, after you have seen how it moves. The assembly of head, shoulders, arms and hands is all the armature your marionette will need. The rest of the ghost consists of flowing fabric draped around the head and over the shoulders and arms. Basically, it forms a shroud. The Shroud Here is the place for more artistic calls on your part. The hood could be an expansive cowl, or a tight-fitting wrap. At this point, attach a string (thin nylon rope) securely to the top of the head, and at each wrist, and find a convenient place to hang the head-arm assembly while you drape the fabric over it. Cut another short piece of coat hanger, and make hooks on both ends. Glue one of the hooks into the top/center of the wig form with Tacky. You'll have to punch through the drapery to do this, of course. Allow the assembly to dry before hanging. Using a single piece of fabric, form a hooded cloak over the head form. Drape 'sleeves' around the armature to the wrists, and allow it to trail around the figure. It should also be gathered around the neck, as well, to cover the base of the wig form. For the present, you'll have to let the hood skirt around the hanging string on the head. After you have decided on the drapery, you will punch a hole in the hood so that the hanging hook can protrude through it. It is, of course, possible to construct the shroud in separate sections, leaving the hood until last to simplify matters. If you choose to do this, be sure that the garment looks as continuous as possible. It should flow, and not be bunched up. This is another place where your creativity should be given full measure, for there are many ways to shape the shroud. Once again, take your time, and experiment before cutting the fabric to its final dimensions. Beneath the neck, it does not matter if the shroud begins to open up a little, but it is important to cover the neck line itself. At the bottom of the shroud, using a measurement equal to the height you wish the specter to have, use a scissors to shred the trailing edges into tatters, in a ghostly fashion. Remember that this will look entirely different under black light, after being painted. Your ghost will not look very interesting in regular light, so don't despair if it seems disappointing at this stage. You will end up making more adjustments later, with the figure bathed in UV and floating from its rig. We will also cover installing the eyes in the next section, as we discuss the animation, painting and lighting. Preliminary Testing Remember that the ghost is a marionette, and must be able to move freely. Try flying the completely draped puppet by hand from a suitable ladder. The arms should move readily in all directions, and not hang in any position. Hidden weaknesses in the armature's linkages will immediately become apparent in this test. If there are positions in which the shoulders or elbows catch or lock, adjust the angles of the joints by bending the wire. Be sure that the loops are tightly closed so that the closures do not unhook. When the ghost is being driven by its animation rig, it may assume a number of unexpected positions, so smooth operation is imperative. Also, make sure that the figure looks as 'natural' as possible. Play with the shroud and draperies until you are satisfied with the look of your figure. The Flying Crank The inspiration for this device came to me while riding through that scariest of all Disney dark rides, "It's a Small World." All kidding aside, when I ride any attraction, I keep my eyes open for exposed mechanical workings. The 'flying crank' is not really 'lifted' from Small World, but is an adaptation of a principle I saw in use there. If you get a chance to ride this attraction in the future, look up at the ceiling and examine the flying rig for the magic carpets. This is the device that makes the magic happen. The mechanism is really fairly simple, and the most important issue is that of the counterweight. The small motor I recommend (as well as most rotisserie motors) may not be able to lift your draped ghost marionette, if you have added bulk, or have used too heavy a fabric. If you find the motor is straining, you should weigh your figure, and construct a simple counterweight - perhaps some small rocks in a can, for example. Affix a handle to the counterweight so that it can be suspended. The Crank The arm of the crank, as mentioned in part one, is a piece of flat aluminum stock, 1 inch wide. The best lengths for this part seem to fall between 13" and 15". No two builders agree exactly on the length. The ghost and its arms will rise and fall about twice the length of this arm, so check the arms of your specter, think about where it is going to be suspended, and limit the length of the crank arm accordingly. With too long a crank, the ghost will move unnaturally, and its head may lean back excessively at one part of the cycle. Experimentation will be required. You can always tap an extra hole in the crank for the pivot assembly closer to the motor, if it becomes necessary to restrict movement (more on the Pivot below.) The entire mechanism is shown, as viewed from below, on the previous page. The illustration below shows the rear-counterweight version of the mechanism. The ASCII diagram below shows both counterweight options mentioned in the text rear of motor platform (away from audience) -------------------------------------------------------------------- | | | Counterweight Pulley ----> o o <- Head Pulley | | (option 2) | | (Option 2: You will use | | two side by side pulleys | | here, with double lines | | from the head. One goes | | to the Pivot of the crank, | | and the other goes in the | | opposite direction, through | | the second pulley backstage | | to the counterweight.) | | | | | | 0 <- Motor Output Shaft | | / | | o <- Left Arm Pulley / Right Arm Pulley -> o | | / | | / | | / | | / | | / | | / <- Crank Arm | | / | | / | | / | | o <- Pivot; all lines meet and are tied here | | | | o <- Counterweight Pulleys -----|-> o | (Option 1) | -------------------------------------------------------------------- front of motor platform (near the audience) To attach the crank arm to the motor shaft, you will need to drill two holes in the arm, spaced to accept both legs of the small U-bolt. It is important to make sure that when the bolt is attached to the motor shaft, the crank does not drag against the platform. This will probably mean that you must drill the holes closer to one edge of the bar than the other. If the material of your motor's mounting surface is thick, and thus limits the length of the shaft protruding through the hole, you can cut away some of the width of the aluminum at the attachment point. Be careful not to overdo this, however, as you may weaken your crank. The clamp for holding the arm to the motor shaft is shown in detail in the ASCII diagram below: Attaching the Crank _________ / _____ \ / /____ \ \ | |/ \ | | <-- U-bolt Motor Shaft ---------|-|| || | -----------\ | |\ / | | \-------------------------------------------------- /------------------------------------------------ -------------- Aluminum Bar ^ || || || || 90 degree twist Nut Nut in the aluminum bar stock here Note that the aluminum stock must be twisted 90 degrees so that the wide dimension of the end holding the pivot assembly is parallel to the ground. Use the vise and a pair of pliers to do this, and take your time. The pivot consists of little more than a bolt attached to the bar through a hole. The ropes attach to a wide fender washer on the bolt, through which small holes are drilled to accept small wire rings. These, in turn, hold the ropes (or nylon twine) which run to the pulleys. Of course, the pivot's attachment washer must ride high enough that the rope/twine does not snag on the center of the crank. If you wish to make the pivot operate more smoothly, add a piece of nylon tubing over the threads of the bolt, and pick a fender washer that fits well around the tubing, but not too tightly. The lines you attach to the rings on the fender washer must be thick enough that they do not slip off the pulley wheels and snag. If you want to use thin lines to support the marionette, attach these to the thicker lines at a point below the pulley. It is easy to determine the length of thick line required. Position the crank at the point farthest from a given pulley, and cut the thick line so that there is a bit to spare beyond that pulley. Attach the thin line at this point. The Pivot Assembly side view, dimensions exaggerated ---- || || <-- Two nuts, locked against each other || || | | ______________ |______________| <-- Wide washer, attachment points drilled through it | | <-- Bolt (can be optionally covered with nylon tubing) || || <-- One or more nuts, depending upon how high washer rides ________________________________ _ _ _ _ _ |_______________________________ _ _ _ _ Crank Arm (Aluminum) || || <-- Nut ___ About the counterweight Referencing the motor platform illustrations above, note that there are either 3 or 4 lines attached to the washer on the pivot assembly, depending upon how you decide to place the counterweight. If you use the front counterweight version, there will be a fourth line which runs to the front of the platform from the fender washer on the pivot. This runs through a pulley which turns the line 90 degrees to the right (or left), and leads it to a second pulley located 'in the wings,' where the counterweight is allowed to move up and down, out of sight of the audience. If you choose to do the rear counterweight, you will need two pulleys, side-by-side, and two pieces of nylon rope/twine to attach to the head of the ghost (refer to the illustrations.) One line goes through one pulley to a separate single pulley backstage, and it is there that the counterweight is attached. The other line goes the opposite direction through the second pulley, and attaches to the crank pivot. In this version, only three lines attach to the pivot's washer. Note: A number of builders have made good use of this extra line, and attached it to visible props which move up and down, along with the ghost. The motor and the counterweight work together to raise the ghost in both versions. The counterweight should be roughly equal in weight to the marionette. This serves to remove unwanted burden from the motor, in much the same manner as an elevator's counterweight offsets the mass of the car which the motor must lift. If you use the suggested Dayton gear-motor, the gearbox will not get warm enough to create a hazard with the wood. The motor itself is located above the gearbox, and is thermally protected. If you use a rotisserie motor or some home-brewed mechanism, be sure to test it under load for hot spots before installing it in your attraction. What happens when it runs? The movement of the marionette, when suspended from this slow-moving apparatus, is amazingly natural-looking. The body of the ghost slowly rises and falls, and the arms gesture independently of that movement. You really have to see the effect to believe that such fluid movements can be achieved with such a simple rig. If you wish, you can mount the arm pulleys in different locations around the periphery of the crank arm. What this does is change the phase relationships (relative timing) of the moving parts. Experimentation is worthwhile. You will need to work out the rope/twine length so that the specter flies within the area you desire to use, her arms neither too high nor too low, at their extremes of movement. The Eyes There are two ways to go with this part of the project. You can have steady-state glowing eyes in your ghost; or you can have eyes that flash with a pre-recorded (or live, through an offstage microphone) speech. Both approaches require that you install L.E.D.'s in both of the figure's eye sockets. Carefully solder a long (6' or longer) wire lead to the _short_ lead on one L.E.D. and to the _long_ lead of the other. Now, solder a 1.5 foot wire to the remaining leads on each L.E.D. With electrical tape, completely wrap both exposed soldered leads on each L.E.D. to prevent shorting. NOTE: The above step is important - you want to connect the short lead (cathode) of one L.E.D. to the long lead (anode) of the other, using the wires that emerge from behind the head. For those who will use batteries and a trim pot (or resistor) for 'constant on' eyes, the positive terminal of the battery must feed the long lead (anode) of the L.E.D. You must know which wire is which! The formula for deciding the value of the ballast resistor for a given D.C. voltage supply will be discussed below in the Appendix ("L.E.D. Math for Imagineers"), with examples. Using a long ice pick or knitting needle, punch holes through the head assembly from the sockets to the back. Next, finish the painting of the figure, as described below, before inserting the L.E.D. assemblies into the sockets. When you have finished painting, and the figure is completely dry, attach the back ends of your leads near the point of the knitting needle (or of a long piece of stiff coat-hanger wire) using electrical tape. Make sure that you tape the wires to the chosen guide tightly, so that the needle or wire does not hang on the fabric while going through. Use this assembly to push the wires through the holes in the head so that the leads exit the back of the head. Be careful not to damage the L.E.D.'s, the wires, or the solder connections while doing this. Remove the electrical tape from the guide, and extract it, being careful to hold the wires so they do not pull back out with the guide. After the needle (or coat-hanger wire) guide has been removed, pull carefully on the electrical leads that emerge from the back of the head until the L.E.D.'s rest in the bottoms of the eye sockets. Now, make the electrical connection between the short lead from one eye to the long lead of the other eye (connect the two short wires right near the back of the head.) You will end up with only 2 long wires trailing to the power supply or amp driver system (for voice version.) Remember, keep in mind which wire is which at all times, if you plan to use the non-voice D.C. version. Setting Up the Talking Version With the L.E.D. hookup completed, play a tape through the amplification system of whatever the ghost is to say. Adjust the trim pot so that the eyes flash on the words: start with the eyes dark, and slowly 'turn up the volume' of the ballast potentiometer until the eyes just begin to flicker. Do this with the system volume set to the level you expect it to run at during the operation of your attraction, and all should go well. You may find that you have to turn the potentiometer nearly all the way to the "full up" position for the flashing to begin. This is normal in many cases. I have suggested a potentiometer value that will most likely handle a wide range of settings on the amplifier, from a whisper to a loud scream. If you find even the 10K pot overloading, switch to a 100K or higher value potentiometer. If the eyes don't light, check the continuity of the wiring, check to see if your solder connections are still holding, and be sure that you aren't using a bad (open or blown) L.E.D. in one or both eyes. Painting The Figure: An approach to using fluorescent paint Really, the best approach to painting a fabric prop that will be used in a blacklight setting is to paint it in a blacklight setting. Even before you begin painting, when visiting the fabric store, take along a small portable blacklight, and expose a bit of the fabrics you sample to it. You may be surprised at the results. If you want to start with a dark surface, be sure your fabric is not impregnated with 'bluing' (a fluorescent dye commonly found in laundry detergents) or a fluorescent factory dye. With this in mind, and with your draped figure ready to paint in a blacklight environment, consider technique. Don't just saturate the surface with the chosen color until it is submerged in paint. If you want subtlety, and are starting with a non-fluorescent surface, use a very light mist, by spraying from a distance when using aerosol paint, or by using an airbrush with a very low paint-to-air mixture. Watch under the blacklight as the effect builds up on the figure or object. Stop when you achieve a mysterious glow. Remember that fluorescent paint is a visible light source, just like a light bulb is. If there is too much of it, it produces too much light, and will reveal details that you may want to leave hidden, killing the atmosphere you have worked hard to create. When painting with fluorescent paints, remember that adding color is not the same as with ordinary non-fluorescent colors. When you add fluorescent red, blue, and green in the right mixture, you don't get a murky brown - you get white. Yes, like a color TV, which uses red, blue and green phosphor dots to get colors, you are painting with light under blacklight. Take a scrap of material and experiment. You will be surprised at what may be done with light mists of fluorescent paint. I suggest that you use a mixture of blue and green on the specter in this example. Yellow (which tends to look slightly green as a fluorescent dye) might produce an equally attractive ghost. This is your call. You can also use flat black to produce the effect of shadows under blacklight. It can help correct places that are too bright. Be sparing, and take your time, and if in doubt, experiment on scraps. When you finish with the painting, you will install the L.E.D. eyes, as mentioned above. My suggestion is that you paint the interior of the eye sockets flat black, so that the eyes seem to float within them like mysterious points of fire. You might want to blacken the inside of the open mouth, as well. The effect is good, and you will probably agree when you see it. Preparation for Public Operation Run-test the specter before it goes into service. Make sure the pulleys don't hang, and that the armature works without snagging. Run your voice setup (or constant-on eyes) with the figure in motion, and be sure your wiring is robust. If you use a battery for the figure's eyes, be sure to disconnect it at the end of the evening when you shut down your haunt. Observe Safety Precautions * Don't locate the hot part of the motor drive within a foot of anything flammable! I realize that the motor board is wooden, but I am referring to rising heat from the motor sitting atop the gearbox. Avoid using paper and draperies above the mechanism! Although the Dayton motor doesn't get hot enough to ignite any regular materials I know of (in normal operation,) there is no point in taking risks. * Turn off all power when you shut down. Check the figure continually throughout the night for malfunctions or hang-ups that might cause overheating of the mechanism. * Don't point blacklight sources into customers' eyes. Unlike white light, blacklight does not warn the iris of the human eye to contract normally, and may cause the person to have the effect of a temporary loss of visual acuity. This can be like the effect of staring into a car's headlight if the blacklight source is strong enough. Even though reasonable exposure to long wave UV (blacklight) is harmless, be kind to your customers! * Locate your ghost where it cannot be mangled by the grasp of a passerby. If you spend a lot of time on a figure, don't subject it to possible abuse. * Finally, enjoy your creation! Spend time looking at your actor/actress in action. Play with the rig, and make little adjustments until she (or he) is playing to your audience the way that you, the director, wish. APPENDIX For those of you wishing to use L.E.D.'s in any Halloween project, the following information will be invaluable. Walls of 'bat' eyes and many other such effects are possible with these little wonders, which commonly outlast miniature light bulbs many times over. If you've never played with them, here's your chance to experiment. L.E.D. Math for Imagineers R (ballast) = V (power supply) - V (L.E.D.'s) / 15 x 10^-3 (or .015) ------ V (L.E.D.'s) values (Multiply these values times the number of L.E.D.'s you use in series.) Red 1.8V Yellow 2.0V Green 2.2V Blue 3.4V (Good luck finding blue ones, but they look great!) EXAMPLES: For 2 Red L.E.D.'s on a 12V supply, use a 560 Ohm resistor [or: 1.8 x 2 in series = 3.6 V of Red L.E.D.'s, so... (12-3.6) / .015 = 560 Ohm or 560 Ohm ballast required] For 2 Red L.E.D.'s on a 9V supply, use a 360 Ohm resistor For 2 Red L.E.D.'s on a 6V supply, use a 160 Ohm resistor 2 Red L.E.D.'s on a 3V supply need no ballast - it will probably work, despite the predictions of the formula, but it will eat your battery alive! In other words, you should use at least 6 volts or higher to be practical. NOTES: The LONG lead on an L.E.D. is the ANODE, which expects to see the positive (+) terminal of the D.C. power supply or battery. As mentioned above in the text, the anode of one L.E.D. must be connected to the cathode of the other for the pair to work. L.E.D.'s are, as their name implies, diodes, and thus they will only pass electrical current in one direction. DO NOT connect L.E.D.'s in parallel.