[derefr]

This article's throwaway notion of glow-in-the-dark pins has got me thinking about how to make a surface with light-up LED pins that can be stuck in arbitrarily.

- You could use (cleverly-braided+insulated) regular LEDs if there was a breadboard or something behind the map, but that'd be both huge and inconvenient.

- Maybe LEDs with inductive coils and a large backing induction mat?

- Given a metallic backing, and a regular fridge-magnet-like magnet, is there some way to trade some of the magnetic force the magnet is exerting on the backing for electrical power? Or maybe power a light using the normal force of the backing on the magnet. Either way, this would probably have the side-effect of reducing the coercivity in a regular permanent magnet way faster than otherwise. (You can make the whole backing surface a weak electromagnet, though! I wonder if that's more or less energy-intensive than making an induction mat of that size...)

- Maybe ignore conductive power, and try for radio power? RFID-powered LEDs? Crystal-radio-like LEDs? Or even just phosphorous-coated pinheads (not the matchstick kind; the CRT kind) with an infrared lamp or blacklight on the other wall?

- Or maybe, if you don't care about the LEDs only lighting up when on the wall, you could just make them "permanently" lit in the same way some exit signs are: put a tiny little bit of something radioactive in there, and then surround that with fluorescent gas in a glass shell.

- A chemical solution would be very interesting for its own sake. If there was potentially chemoluminescent fluid in the backplane (which would then have to be a gel/sponge), and the pins could pull it in via capillary action somehow—maybe the heads on the pins could be squeezed, making them effectively into little bulb syringes—then fluid could end up in the pinhead and react with something inside.

[MichaelSalib]

Around 2003 at MIT I spoke with a guy who told me about a home lighting system that the French were using. Basically, you take an entire wall in a house and sandwich thin conductive layers between insulator layers. Then you have these special light fixtures with a sharp pronged tip that exposes three different wire heads at different lengths.

You just stab one of these fixtures into the wall anywhere you want; each of the three prongs travels to a different depth and makes contact with a layer representing the hot, neutral, and ground lines so that your light fixture is now plugged into 220 Volt wall socket current.

At the time, I remember saying "that sounds totally insane". I still think it is. But if you made a special map backing board rather than entire walls and ran a lot less power through it....

[icebraining]

Given a metallic backing, and a regular fridge-magnet-like magnet, is there some way to trade some of the magnetic force the magnet is exerting on the backing for electrical power?

You need movement to generate electricity, otherwise it'd be a perpetual machine.

An alternative would be to have a "surface of light", ie, a source of light all along one of the walls of the map and passing right over it (not actually illuminating the map); then any object sitting on the map would be illuminated.

[ianbicking]

Maybe put a strong light behind the map, and use a fiberglass pin? Kind of like a Lite-Brite.

[simplemath]

That would be a reasonably practical solution with a lowish profile lightbox as the mounting.

Hmmm.

[snops]

> You could use (cleverly-braided+insulated) regular LEDs if there was a breadboard or something behind the map, but that'd be both huge and inconvenient.

Theres a simpler solution that uses the same idea. Have pins that look like mono audio jacks, so the "tip" and "ring" are separate. Put two layers of conductive material down on the map, one on each side of the insulating board, and apply a voltage between them. When you stick in the pin, your "ring" contacts the closest layer, the tip the furthest, and so you have a voltage available to power the LED in the head. The voltage would only need to be about 3V or so, so its perfectly safe, you just need a small fuse in case of shorts.

Manufacturing a conductive "ring" on a pin would be difficult with machining, so using a conductive paint on top of an insulating paint would be the best option. The hardest issue would be ensuring a reliable contact with the ring, as the contact surface would be very small.

[Retric]

I would probably go for black light as the cheap / easy solution, but you would need to keep the map clean.

[pavel_lishin]

I bet this guy would have some ideas for light-up LED pins: https://www.youtube.com/channel/UCNAAxVKWPAbaZiB90_kjDJw

[SixSigma]

LEDs are cheap just tape a battery to one

http://en.wikipedia.org/wiki/LED_art#LED_throwies

[kej]

Probably overkill, but you could get a similar effect with a high resolution projector aimed at the map. Light up certain spots with color, and leave the rest black.

[dagw]

Except that if someone walks up to look at the map they'll block the projector beam and you lose the effect

[FireBeyond]

I wonder if you could mount it on the ceiling, or even in, angled steeply (so you'd have to get very close to create shadows). For imagery, distortion would make this impossible, but if you're just projecting white light...

[theatgrex]

you could just have self powered led pins that have a switch in the head that turns on when you press the head down ...this way you could also selectively light up pins!