Introduction: Free-form Pluggable LED (Power) Plate
This Instructable describes a way to make a flexible powered surface that you can stick things into at any point to power them. Shown here are LED's. It's an entry for the Epliog laser challenge.
I was thinking of the Lite Brite, of how it forces you into rectilinear shapes, limiting creativity. How can you make something that would let you plug a light, an LED, in anywhere on the surface? This is what I came up with.
(I don't have a catchy theme song like Lite Brite though)
It's my first instructable so go easy on me. :)
Step 1: Materials
- cork, foam
- carbon fiber (maybe could use another conductive fiber)
- spray glue
- clear tape
- box cutter razor
- bunch of LED's
- 9v or power supply
- soldering iron, solder
- connectors (see pics)
- alligator clips
- 220 ohm resistor (value depends on input voltage)
- pencil, pen
- super glue
- toothpicks or pins (to spread super glue)
Optional but helpful:
- some small (5"x5") wood boards
- file (sharpen ends of LED leads)
- volt meter (to know what's going on)
- square (to make square cuts)
- silver paint marker to mark bright lines on carbon fiber sheet
- vise (hold things while soldering)
All the materials are pretty common except the carbon fiber and that you should be able to order from any of dozens of suppliers.
I had just ordered a bunch of sample carbon fiber pieces and discovered they were conductive, which gave me this idea somehow. The carbon fiber I got from hp-textiles.com as a sample piece for 1.50 euro (about $2) for a piece roughly the size of a normal piece of printer paper (A4). The exact kind I used is HP-T240CE (http://www.hp-textiles.com/shop/product_info.php?info=p515_240g-m--carbon-fabric-twill--hp-t240ce---slippage-resistant.html) which has a light binder in it. Normal carbon fiber works too (I tried some other samples) but I liked the one with binder since it didn't fray wildly like the normal carbon fabric did.
Step 2: Prototype
I quickly made a prototype and it worked--very encouraging! Also the carbon fabric seems to be very conductive, 3-6 ohms between probe tips about 8 cm apart. Not shown, I also tried to burn it with one of those jet-flame lighters and it resisted completely as far as I could see. The only problem is that it frays like crazy so if you cut it you should tape the edges first and tape along the cut line (although removing the tape could lead to fraying).
Step 3: Cut Carbon Fiber and Sandwich Material
I decided to make a 10x10cm board. This went nicely with the sample carbon fiber which was 20cm wide.
I tried various materials but thin cork worked best for the inner sandwich material. I got it from a hobby shop and is 2mm thick.
I used a ruler and razor to cut the cork and carbon fiber. The carbon fiber I first marked with a silver paint pen (great for marking dark materials!) then put tape over the cut line so it wouldn't fray after being cut. Carbon fiber really frays and falls apart so watch out. For the cork, and many elastic materials in general, I found that extending the razor blade then cutting at a low angle makes a much cleaner cut and helps prevent tearing of the material or catching of the blade.
Also pictured is the carbon fiber spec sheet (English available here: http://www.hp-textiles.com/shop/product_info.php?info=p515_240g-m--carbon-fabric-twill--hp-t240ce---slippage-resistant.htm, click the small British flag to change to English) and the fiber close up where you can see one side with some kind of binder drops and the other side the "raw" carbon fiber.
Step 4: Assemble Sandwich
The assembly consists of a two sheets of 2mm cork in the middle with a sheet of fiber on each outer side.
Before gluing I soldered the wiring bits and looked how they were going to fit. I cut a small notch in the cork for the resistor and also for the wire. I used spray on glue to put each layer together. I sprayed a thin layer of it on both sides that were going to be pressed together then waited 8-10 minutes then pressed them together. I used some clamps but I think you could also just push them together with your arms or maybe stand on them. The clamps actually cause the cork pieces to slide across each other a bit and get out of alignment, but nothing disastrous.
I then sprayed one side of the cork assembly, being careful not to spray the wires--I did not want to spoil the contact. I also did not spray the carbon fiber for fear of the glue migrating up into the fibers and later on reducing contact with the led legs that would be inserted. I let this dry too for 8 minutes or so. Then I pushed one of the wires onto the sticky cork so it would contact the carbon fiber when the carbon fiber was pressed down. Then I carefully aligned the small carbon fiber square over the sticky cork and pushed it down.
Step 5: Power Plate Assembled
The assembly looks ok and by pressing LED's on it manually I could see that it worked.
Step 6: Power Plate LEDs
Unfortunately since I did this whole thing last minute I had to scavenge for LEDs. Luckily I had some at least.
This is the key part: the LED's need two things:
1) one leg shorter than the other so it does not touch the bottom carbon fiber panel
2) the longer leg must be coated with an insulator so it doesn't touch the top carbon fiber panel
I cut the LED's at a diagonal so the ends would be more pointed and penetrate the fiber and cork more easily. You could also file them a bit to make them sharper, if necessary. I filed a bunch then found that cutting them at a diagonal worked well enough.
NOTE: You have to keep track of which LED leg is which. Usually there is a flat bit on the LED plastic housing (see pic) and/or one leg is shorter than the other. I actually cut the "short" leg so it was the longer leg (that is, touching the back carbon fiber panel). I hope this is not confusing. For this construction it really didn't matter which way the polarity was as long as it was consistent between LEDs.
Step 7: Insulate LED Legs
This was probably the hardest part. I tried super glue and lacquer and found super glue worked better. It would have worked far better had I had more time to let it dry overnight. The problem is super glue works well if you press on it but if you just dab it on, like here on the LED legs, it takes a long time to dry. I tried using a hair dryer and I think it helped a bit. I had to go back and put two or three coats on some times. Also, I initially dipped the whole leg in then sanded the bottom bit off so there was bare metal but then found it was better to just very lightly, with the tip of the super glue bottle, dab the LED leg then let it dry.
Try not to get it on your fingers. Or if you do have some acetone on hand. :) You shouldn't have drops of super glue since it wicks all over and will go on the LED and the other leg. I ended up not needed it, but pictured is a way to hang the LED upside down on a lump of clap so the glue drips down to the bottom (I DO NOT recommend this since you want glue at the top of the leg and not the bottom, but I show it since maybe it's useful in other cases).
Although this step was hard, there's not a lot to show. You simply have to carefully apply the glue over the LONGER leg (leaving the bottom millimeter or so free), let it dry then test it (see next step). Before testing, to be sure the contact is good, I used the razor and scraped the bottom mm or so of the long leg, and the top couple millimeters of the short leg (where it need to contact the upper sheet of carbon fiber). You could also use a file (pictured) but I found the razor to work better.
Step 8: Firing Up the Power Plate
I plugged it in and IT WORKED! I was very happy since I have no time to repeat or fix much. It didn't work completely--the insulation on some LED legs was not covering where it should and I had to re-apply super glue, let it dry, scrape the glue off on places it shouldn't be then try again. Sometimes I had to do this twice, so three coats of glue. I think the thinner the glue the better as far as drying fast goes. Maybe if you had more time you could put a lot on to ensure insulation. You know you have a problem when you stick an LED in and the light either flickers or, if you have multiple LEDs already in, the lights all go out. Back to the glue!
Step 9: Power Plate in Action - Results!
It works...I am shocked. Now is time to play. I wanted to have more LED's to make designs with but I didn't have them on hand nor had time to prepare any more. Actually, what I made is not quite as fancy as what I imagined making but was all I could manage in one day.
For the power supply I am using a small wall adapter set at about 9V. I also connected a 9V battery and that worked as well. One single LED was drawing about 10mA and they do dim some when you connect more but not so bad. See comments below for a link to a video I made attempting to show the dimming effect.
The LED insertion is a bit fiddly but works quite well. There could be several improvements or modifications like: a metal back-plane to aid contact on the back (but then it wouldn't be flexible), multiple layers of carbon fiber to make the contact points bigger, magnets on the back so you can mount it on a metal surface, battery pack built in, black felt over front surface to prevent fiber loss from shredding (which happens a bit), pack fibers with graphite powder to see if resistance even goes down more, etc. You could also use a different conductive plane material like conductive rubber/elastomer/putty...if such a thing exists. I'm not sure it would withstand the poking as well as fabric though.
Here are a couple of videos which I couldn't seem to add using the Instructables video-add functionality:
I realized partway through that if you're just placing LEDs it's similar to Lite-Brite--except it doesn't restrict you to a grid, you can make it any size, you can make it yourself, etc. But the point is not just to make LED light displays. It's the flexible, pluggable power panel concept where you could plug in anything with one insulated leg, e.g. could be a electric piece--clock, motor, fan, etc. It could go behind something, like a world map (which you could stick small clocks on set to the time where they are located?). Or maybe under a board game with electric pieces. Or an entire floor, where you could just set down a lamp with prongs in the bottom for example, and it would be powered. You could also have devices on both sides if you swap the leg insulation around. It also has the advantage of being a speedy power connection since you don't have to worry about orientation when you insert a device, you can just jam it in. Maybe something for simplifying mobile robot self-recharging?
You could also easily make a strip of LEDs like those you buy.
I suppose any carbon fiber product is game for being hacked into something electric.
I tried to think of some other uses now for it but my brain is getting near it's MTBF (3:32a.m.).
So, thanks a lot for taking a look and I hope you found it interesting and maybe even exciting.