One day I was perusing the internet and stumbled upon a video; Water Light Graffiti by Antonin Fourneau, created in the Digitalarti Artlab. When water is painted, sprayed or sponged on LEDs light up. This seemed like such a cool project, I was inspired to try to make my own; cheaper, easier, desktop version.
They way this works is that the one lead of the LED is separated from the power by a small gap. When you apply water, water forms a bridge that closes the circuit and lights the LEDs.
On their web page there is a link to another video where the artist discusses the process and prototypes he went through for this installation, however the video is in french (unfortunately, I didn't understand a word of the video). I did however watch what he was doing and it seems like the working prototype was made using a printed circuit board, though one of the early prototypes was made with copper tape, which fit much better with my plan to make a cheap and easy version.
For my version, the materials were acquired inexpensively, from a dollar store and the LEDs and copper tape from Ebay. It is easy enough that you don't even need any special skills or equiptment and you don't even need to solder anything.
In one article I read about the Water Light Graffiti installation drew similarities between it and Buddha Boards upon which you can draw on with water and once the water evaporates the image fades. So I modelled my project after a desktop Buddha Board.
Step 1: What you will need
(Overall cost ~$10 cdn)
Step 2: Test
So I wanted to test this out first. I used a 3v button cell, a RGB LED and used water on the tip of a paint brush - it worked quite well.
For the project I ended up using a 5.1V wall charger from an old cell phone. I mistakenly though I would need to use resistors, (3v LEDs, 5.1V power equals 120ohm resistors) I didn't factor in that the water has enough resistance itself. Unfortunately, I didn't figure this out until I went all the way through to step 8 and my LED canvas wasn't working as my test one had done. So I pulled out all of the resistors and now it works fine (though it is a bit messy and I had to solder the leads to the copper tape because I couldn't pull the tape off the back).
Some quick tips about LEDs
Just a quick word about LEDs, if you don't have much experience with them, the longer lead is positive (which would hook up to the positive end of a battery) and the shorter lead one is negative. The voltage can vary with the colour of the LED, when you buy them you are usually given that information (for example white and blue is about 3V, red and green is about 2V). If you are connecting LEDs in an array they should be about the same voltage. I used white ones that where 3V and RGB colour changing ones that where about 3.1V and that worked fine.
Step 3: Prepare copper tape
-Unfortunately, the copper tape I ordered came folded in an envelope so there are wrinkles where it was folded which I can't remove, so when you tape it onto the canvas it doesn't look as nice as I hoped. If you pay more you could by the tape in rolls so you wouldn't have this problem.
Step 4: Cutting circles
Step 5: Trimming the circles
Step 6: Drilling holes and preparing LEDs
Step 7: Adding LEDs
Step 8: The back
This is the part that I did wrong initially by adding resistors. I ended up having to solder the negative leads to the copper tape strips since I couldn't peal of the tape without ripping (I didn't have any extra). So if you do it the right way, which I will describe below, you won't need to solder. Use the template as a guide.
Step 9: The power supply
Step 10: Trying it out
Now it is time to try it out and have some fun. A paint brush is one way to interact with the canvas, try a spray bottle (see first video) or your finger (second video).
Why not try a little science experiment comparing how well filtered water works (or doesn't work) vs tap water, how about rain water, why not add a little bit of salt (be careful, not too much) -what happens?
It is a good idea to wipe off excess water between use, the copper will eventually corrode. I already notice the tip of my paint brush turning blue.