Electroluminescent Wire Lighting
Here’s a different idea for model lighting: Electroluminescent Wire. I can’t take credit for this, as it was suggested to me by Don at Akihabara Station. But it’s a cool idea. EL wire is basically a phosphor-coated wire in a transparent or tinted outer jacket. Small wires wrap the big one inside the jacket, and an AC signal of hundreds or thousand of Hz will cause the phosphor to fluoresce. The wire carries a fairly high voltage (typically 120V) so some caution is required, but the current needs are minuscule (it can be driven by AA batteries). In addition to the default “blue” color, other colors can be made using a colored or fluorescent jacket. You can find a bunch of suppliers online by Googling for “EL Wire”, including the usual electrical hobbyist sites.
I haven’t yet bought any of this to play with (too many projects, too little time) and I don’t have a good idea for an immediate application on the layout. But it’s definitely something I want to try eventually.
WARNING: Operating an inverter with no wire will typically burn it out. Operating one with less than a minimum load (minimum length of wire or equivalent) could possibly damage it (some comments suggested it would, others that it would not; it seems reasonable that if no load causes a problem then too small a load would too). Info on this isn’t easy to come by, as in most applications people need to worry about their wire being too long for the supply (and thus dim) and not the opposite. The basic issue appears to be that most inverters use a resonant circuit, where the wire provides part of both the resistance and capacitance for the resonator. Too little wire means the circuit has too little resistance, or perhaps too little capacitance, or both.
Don has since done some work with EL Tape, and written it up on his site. EL Tape isn’t quite made the same as EL Wire, and “white” EL Tape appears to have a garishly blue cast to it from his experience.
EL Wire is dim, and probably more suited to use as a sign or accent than as interior illumination in a model. It comes in a variety of colors, including white (although that seems to be harder to find than the others; it took some looking to find 1.2mm wire in white).
It’s also fairly long-lived, at several thousand hours, which makes it a good choice for use inside a model. It could also be applied to the outside of a plastic structure and used as accent lighting, since it operates “cool” and won’t damage the model. There’s also a self-adhesive “tape” version, but this is apparently pre-sized and can’t be easily cut to size (the stuff I saw was 1cm but in a 1.5cm wide jacket). There is also a sheet form. This could be used as backlighting for a sign (made by printing a shadow mask on clear plastic, for example).
EL Tape is manufactured slightly differently from EL Wire, so the colors of one won’t be identical to the colors of the other. In particular, as noted above, “white” EL Tape is more blue than white.
EL Wire was originally an “aqua” colored light source, that was tinted by wrapping it with a colored plastic jacket. An unjacketed wire could have the color varied from green to purple by adjusting the frequency. White was produced by a tinted jacket, just like other colors. Newer “white” wire now uses a different approach for a brighter white. This is apparently a “pink” color when unlit.
I’ve seen a note (which appears to be for the older form of wire) that says brightness peaks at around 2,000 Hz (a cyan color), above that the color moves towards the violet and the overall light output drops.
EL wire isn’t bright. The manufacturer rates it at 70 Nits under “typical” (800Hz, 100V) conditions. For comparison, an LCD panel is 200 – 300 Nits and an LCD TV is at least twice that. Given that, this isn’t likely to be useful as an area illumination, but could make good “neon tube” accent lighting outlining signs or on structures.
EL wire works in the same way that a fluorescent light tube does; it needs a high-voltage AC electrical signal to light it. This is normally created from a low-voltage DC supply (like a AA battery) using an inverter. It will work best on voltages around 100V, but actual current is very small (milliamps) so small wires can be used safely. Inverters are sized by the maximum length of wire they can drive (which can be multiple separate wires) as more power is needed for longer wires. There is also a minimum length of wire for an inverter, and shorter wires should not be used as this can damage the inverter.
Lead wires don’t count as part of the “length” requirement for the inverter. These can be fairly small, and while I haven’t found formal specifications yet, I’ve seen 26ga offered, so it can be at least that small (I’m curious if it can be smaller for hiding leads on structures). One data sheet implied currents of up to 80mA @ 110V (9W), which would imply you could go down to 30ga in open air, but if it was painted as part of a structure, you might need to be around 22ga to avoid overheating the wire (making it look like a drainpipe on a platform support, for example).
Frequency is also important: higher frequencies make for brighter wire, but a shorter lifespan. The manufacturer notes 50 – 5,000 Hz is “typical”, but lists an 8,000 Hz “very bright” inverter on their site (see references). Most inverters appear to have fixed frequencies (and these will vary based on the length of wire attached due to the way inverters work). However, the Make article (linked in references below) describes how to make your own inverter with a variable-frequency control.
One note I saw was that at 60Hz (and yes, you can drive it off a wall outlet, although that would be terribly unsafe without a very small fuse on the wire) it’s good for 25,000 hours, but at 1,000 Hz that reduces to a few thousand hours or less. However I’ve seen conflicting information. A frequency of 1000 Hz or higher seems to be recommended for good brightness.
You can buy it bulk and solder lead wires to the end, or buy shorter lengths pre-terminated. There’s no standard connector though, so inverter and wire should come from the same supplier unless you plan to terminate it yourself.
EL Wire is available in a variety of sizes down to 1.2mm, and when bent will tend to remain in that shape. This means it could be used to form “large” (in model terms) neon signs. However, there’s a minimum safe “bend diameter” of 5x the wire diameter, so the tightest turn would be 3mm in radius, or a full quarter-inch (6mm) to make a 180° turn. This limits the potential applications (I’m also concerned that they described it as “bend diameter”, when “bend radius” is a more common usage, and since the site was a Dutch one, I’m wondering if they meant “radius” and used the wrong English word).
This is mostly available through specialty suppliers, who often have detailed tutorial information on their sites. I’ve listed a few (Amazon also carries it via third-party suppliers). This isn’t a reference or review–I haven’t done business with any of them, yet–but merely informational. It appears that stock availability varies over time, so you may need to wait to find the color you want in a diameter you need. A number of these also sell EL sheets (squares of flat material) and EL tape (strips of flat material).
A 50’ length of 1.2mm seems to sell for around US$60 – $75. However Sparkfun sells 3m of 2.3mm wire for just $10, suggesting lower prices are out there for bulk purchases. But I haven’t been able to find any (I did find some bulk wire that cost a lot more).
Note: pricing comparisons and stock information as of October 2012.
adafruit.com has a variety of short pre-terminated wires (using a JST SH 2.54mm pitch connector, not the same as the PH used by Sparkfun) and some inverters. Pricing is quite high, but declines to merely high if enough are bought.
Cool Neon sells both wire and inverters (with a fairly large variety of both). Their wire is sold by the foot and prices are a bit high. However while “white” was listed on their color chart for 1.2mm wire, it wasn’t listed on the ordering pulldown except for their largest diameter 5mm wire. They have a lot of different inverters and power supplies for inverters available.
ellumiglow.com has wire by the foot, although at above-average prices. They did not have 1.2mm white, but did have 2.6mm “lavender white” (which appears to be the newer, and brighter form since it’s described as “pinkish when unlit”). They also have a large variety of inverters. Their connectors do not appear to be JST-PH, but may be a JST-SH from the photos.
elwire.com sells wire only in bulk form (very long lengths), and the prices are significantly lower than shorter lengths sold elsewhere (higher in some cases). Their website appears to be “under construction” with a number of empty sections.
Live Wire (elbestbuy.com) sells wire by the foot, but at significantly higher than average prices. They carry 1.2mm wire, but lacked white in all sizes when checked.
SparkFun sells wire and a couple of inverters. Wire is only available in pre-terminated 3m (10’) lengths using JST-PH connectors, but the price is reasonable for that. They do not carry 1.2mm wire, but white 2.3mm wire is available.
Note: The PH connector is a common connector, originally developed by JST (Dutch wikipedia; no English page found), available in a variety of pin counts, SparcFun identifies this explicitly, but photos of some other suppliers suggest they may use a similar connector.
EL Wire is trademarked as LyTec (see their Products page for more info), developed by ELAM.
LadyAda.net (now moved to adafruit.com) has a tutorial on working with EL wire.
Make magazine article on EL Wire. Includes circuit diagram for a do-it-yourself adjustable-frequency inverter.