Typically the re-emitted light is not the same color as the absorbed light, and Step 6 has some pictures, and explanation, of how that works. But it doesn't matter if you slept through Quantum Mechanics, or even if you never had to take that class in the first place. For this 'ible, it is enough to know the color of the absorbed light is blue, provided by a blue LED, and the color of the re-emitted light from the GITD material is green. Visually the effect is very pretty. Especially if you like the colors blue and green.
Aside from the underlying physics, and using big words like "phosphorescent", the next hardest part is actually finding phosphorescent (aka GITD) material, in the form of a flat sheet big enough to doodle on. The best thing I found was this: glow-in-the-dark printer paper. Yes, they actually make GITD printer paper. However there's no monger who sells it near where I live, so I had to buy it from an online retailer. There's more about sources for GITD paper in Step 4.
Another trick is fitting a blue LED into the tip of the body of what used to be a ballpoint pen. As an added complication I want the LED to turn on only when it is pressed against the pad. That way it "marks" in the same manner as a pen or pencil, which marks only when pressed against the paper. If the LED is always on, I get an effect that is more like spray-paint, and that isn't the effect I want.
Another feature I want is for this contraption to be powered from a single AA battery. To facilitate this, I hack apart a cheap single-cell LED flashlight, and pull out its little magic LED-driver module, and then insert said module into my circuit. See Steps 8, 10 and 11, for more on the magic LED-driver module.
When I put all these elements together: GITD sheet, plus clipboard, plus page protector,plus blue LED, plus hacked LED driver module, plus pressure actuated switch... the result is the Phosphorescent Notepad.
It's a toy that I can use to draw doodles in the dark. And it's great fun at parties! Particularly those parties that happen at night.
The last feature/flaw: Drawings on the Phosphorescent Notepad erase themselves!
Given a few minutes the GITD material fades back into equilibrium with the ambient light/darkness. The drawings don't last, unless I take a picture of them, and that is somewhat tricky because it must be done in low light. A picture of a few "saved" doodles are attached to this Intro, and Step 13 which explains the trick to taking these pictures. (Note: If the camera flash goes off, the resulting flood of white light obliterates the drawing. Thus, pictures of phosphorescent doodles must be taken with the camera's flash function turned off.)
Step 1: Prior Art
Some commercial versions of this product include, the Crayola(r) Glow Station(r), and the Uncle Milton(r) Shadow Magic(r). Some promotional pictures of these culled from the web are attached to this Step. Coincidentally the words "Shadow Magic" are the title of not just one, but two, completely different, trashy romance novels. It's just funny the things that turn up in the search results sometimes.
Also worth mentioning: If there exists, near where you live, an institution calling itself a, "Science Museum", you might have an opportunity to experience a room-sized version of the Phosphorescent Notepad. Science Museums love to paint at least one room with phosphorescent paint. For example, the Exploratorium has such an exhibit.
That's the Exploratorium of San Francisco, in the Former United States.
Anyway, I just wanted you to be aware of some of what's out there,and that's the last I'll mention of SEDIFY in this instructable. So if you think you'd enjoy a little DIY, then please proceed to the next Step.
Images for this Step are just promo images, found on the web.
Step 2: Materials
It relies heavily on office supplies, things like the clipboard, page protector, pens, a single rubber band.
It also uses electronic components: the insides of a single-cell white LED flashlight, some capacitors, a diode, a piece of 4-conductor cable that used to be part of the cord from a computer mouse, a few other kinds of wire: solid copper sizes 20, 24, and 30 AWG, a 2-cell AA battery holder, also some brass 4-40tpi machine screws, and nuts, and washers.
Last but not least, is the single 8.5 by 11 inch sheet of GITD paper. Technically that might be "office supplies", but it was a little hard to find, so I'm going to categorize it as an "exotic material". Step 4 provides some links to where I have seen GITD printer paper being sold online.
The pictures attached to this Step, illustrate most, if not all, of the junk mentioned above. The first pic shows electronic parts for buiding the light-emitting pen. The second pic shows a clipboard, a page protector, and a packet containing GITD paper.
Regarding sources for some of this other stuff:
I got the single-cell, white-led, flashlight from DealExtreme, here:
The blue, T1-sized (3mm) LED, I got that from Electronic Golmine, here:
Not sure how long those links will remain valid. What year was this 'ible written?
Step 3: Tools and Skills
I have drawn a couple of diagrams, a circuit diagram, and a also a sort of cut-away view illustrating how the light-emitting pen fits together mechanically. These diagrams are shown in Step 8.
I am hopeful that you, dear reader, can make sense of these diagrams, and all the other pictures and text found in this 'ible.
I try to be clear, but at the same time I don't worry too much about you not understanding what I'm doing.
Really what should be most important, to you, is that you understand what you are doing. Then the success of whatever it is you're working on, will naturally follow.
Step 4: Critical Item: Phosphorescent Printer Paper
I had to do terrible things to get this stuff. Specifically, I had to buy 10 sheets of it a price of about 2 USD per sheet, and pay like 5 USD shipping too! But I guess I must have wanted it really, really, bad.
I obtained my ten, lovely, glowing sheets of Papilio(r) brand GITD printer paper, from here:
I later discovered another GITD paper seller, here:
When seeking this stuff via a search engine, I recommend phrases like "glow in the dark paper", "glow in the dark printer paper", "glow in the dark photo paper". Something like this, is usually what they call it.
The size you (probably) want is a rectangle, 8.5 inches by 11 inches, or 210 mm by 280 mm. That's the same size as a "standard" letter sized piece of printer paper. Moreover this is a size that will fit neatly on your clipboard. And I think that is the biggest, cheapest, single piece that can be easily found, at the time of this writing. Also keep in mind that some places are selling paper smaller than this, e.g. photo-sized 4 by 6 inches. The reason for the warning is you'd probably feel stupid if you really wanted some of this paper, and then screwed up and ordered the wrong size.
If you already have some, or you somehow have the ability to paint, or print, or otherwise "roll your own" phosphorescent paper, or phosphorescent flat surface, then you're one step ahead of me. As an example, this instructable:
is basically a piece of glass painted with phosphorescent paint. Something like that would probably work too.
The picture attached to this step is two promotional images, two brands of GITD paper, Geographics(r) Photoglo(r) on the left, and Papilio(r) on the right.
Step 5: Clipboard, Page Protector, Rubber Band.
The rubber band is a size #32, if you must know.
By the way, these three artifacts: page protector, clipboard, rubber band, these are items you can find at an office supply store, or possibly even in an office.
If it just so happens that you work in, or near, an office, you should of course steal these things from your employer.
Oh, and uh, while you're at it, get some pens too. You'll see why, and what kind to get too, in the Steps that follow.
Step 6: What Color LED Should I Use?
If you want to know, "Why not red, or orange, or white, or ultraviolet?", then keep reading.
You might be wondering what color LED, or what color of light, is capable of exciting/activating this GITD stuff. Does the color of the incoming light even matter?
I was also wondering about questions like these, so I set up the little experiment shown in the picture, and the picture itself does an excellent job of explaining how this all works. From the picture, it appears that the color of light does matter. What it looks like is the light needed to excite the GITD material, must carry more energy, per photon, than the light emitted by the material, which is equivalent to saying the frequency of the pumping light must be higher than the frequency of the emitted light, according to the formula for photon energy, E = h*f = h*c/λ .
Well, I don't know if you can just see that from the picture. Some additional explanation may be helpful.
What I have done in the pictures, is wire together, in series, one of every color of LED I have in my collection. Starting from the left, these LEDs are, by color, infrared (IR), red, yellow, orange, green, blue, white, and ultraviolet (UV). That is to say they are arranged, approximately, in order of increasing frequency. The lowest frequency corresponds to IR. The highest to UV.
The white LED is kind of a funny exception, because it is emitting more than one color of light. But I am guessing that the strongest of these colors is blue. A white LED is basically just a blue LED, packaged together with some phosphors, which when excited by the blue light, emit other colors, including green and red, thus approximating "white" light.
- First I left the GITD paper in the dark for a while, to let it go dark too, to reach a kind of equilibrium with the darkness.
- Then I turned the LEDs on and took a picture, shown here as the top picture.
- Then I turned the LEDs off, and a few seconds later, took another picture, shown here as the bottom picture.
- Top is before. Bottom is after.
The result: Only three of my LEDs seem to noticeably excite the phosphors in the GITD paper. Specifically these are: the blue LED, the white LED, and the UV LED. And you can see this in the picture below.
Undoubtedly, there's some deep physics going on here. One hypothesis is that each emitted photon is getting it's energy from just one absorbed photon, and it is the law of conservation of energy that implies the incoming light must have more energy, per photon, in order to make this happen.
The practical result seems to be that to excite glowing green phosphors, you need your pumping light to be more energetic than green, e.g blue, or UV. A white LED will work too since it produces some blue light. In contrast, my green, yellow, red LEDs are just not doing anything to excite the phosphors in my green GITD paper.
So, for example, if I try to build this 'ible using a red LED stylus, it just won't work.
It seems like the answer is to use either blue, or white, or UV.
I have heard/read that UV leds can emit light that is actually harmful to the eyes, and I'm going to be playing with this in the dark, with eyes wide open, more wide open than they would be in normal light. So I think using a UV led would be bad. Bad for the eyes.
A white LED seems inefficient, since part of my light energy is wasted in frequencies (colors) which cannot excite the GITD paper.
So there you go. Quod erat demonstrandum. That's why I'm using a blue LED.
Step 7: Capturing Shadows
However there is also some fun to be had without the light pen, using just the ambient light in the room.
I pile a bunch of interestingly shaped objects onto my phosphorescent clipboard, and then turn on an overhead light.
Next I turn off the lights. I sweep the junk off the clipboard, and quickly take a picture of it.
The shadows left by these objects are captured by the GITD paper!
These pictures are presented in reverse order: shadows shown in the first picture, objects which produced these shadows shown in the second picture.
Step 8: Plans for a Light Emitting Pen
The first is a cut-away view of the insides of the light-emitting pen, explaining the mechanism of the switch inside the pen.
Basically there is a section of that spring under tension. It is caught in between the plastic "tip", and a "pin" stuck through the shaft. The shaft is attached to the LED/stylus on its left end, and a switch contact on its right end. The spring tension is always pulling the shaft forward, and pulling the switch open. The only time the switch closes is when the LED is pressed against the GITD paper. Doing that pushes the shaft into the body of the pen, and closes the switch.
The second diagram attached to this step is a circuit diagram. The most mysterious about that is the little three terminal "black box" which is the LED-driver circuit. The three terminals I have labeled Vin, Vout, and ground. And it is OK if that part remains a little mysterious. Pulling that module out of an off-the-shelf, single-cell, LED-flashlight, saved me a lot of work, and gave this toy the elegance of being powered by just one AA battery! I think it's sexy! You might not like the fact that there are four wires running back and forth, between the clipboard and the pen, but the 4-conductor mouse-cable is just perfect for that!
You might also be wondering about the extra components I added, two capacitors and one diode, and those are there for a good reasons, which I promise will be explained in Steps 10 and 11.
Step 9: Taking Apart Pens.
The other vital ingredient is a spring, of the kind found in clicky-clicky, retractable ballpoint pens. A few examples of these are shown in the first picture. Only the spring is needed, and I'm sorry if that seems wasteful. It's not like I actually throw anything away. All the pen parts I own get tossed together in a red plastic, toolbox, that looks like a grisly mass grave for ballpoint pens. That's in the last picture.
The remaining pictures in this set involve my efforts to remove the ink from the thin plastic tube shown at the very top the first picture, and this was kind of messy. I think the trick that worked best was pushing a thin wad of paper towel through the tube using a piece of solid 20 AWG copper wire (pics 4 and 5). I also tried placing one end of the tube in my mouth, and blowing air through it, and that got some of the ink out. But in retrospect, I think the pushing the wad of paper through it worked best.
Ethanol (pic 6) does an OK job of cleaning up pen ink, and it is not as toxic, or foul smelling as other solvents.
Step 10: Taking Apart the Single Cell Flashlight.
Hidden deep within this flashlight is the LED-driver module I will use to power my glorious light emitting-pen.
First I unscrew the barrel from the other two pieces which I will call, "head" and "tail". The head is the part containing lens, white LED, and LED-driver module.
The pictures show what I found in the process of pulling this flashlight apart.
Step 11: The Magic LED Driver Module
One of them I label "Vin". Another I label "Vout". And the third, I label it, "ground".
In its former life this module had a single AAA battery and a switch, in series, connected between Vin and ground. It also had a white LED connected between Vout and ground.
Next I get this module running again, using essentially the same circuit it was in, in the flashlight. Only this time the circuit is built on a prototyping board. This is shown in the second picture.
In the third picture, you can see that I have added a number of components. The most conspicuous change is that I have placed a diode and a 0.1 uF capacitor where the LED used to be, and now the LED is connected in parallel with this 0.1 uF cap, but by way of a big long pair of wires. Also I have placed a 1 uF capacitor between Vin and ground.
The reason for these additional components is due to the fact that the circuit I have planned, has some long wires, and the driver produces fast, high frequency signals I don't want running through long wires. The diode and 0.1 uF capacitor form a halfwave rectifier and filter, and I have hopes that the current flowing off this 0.1 uF cap to my LED-on-a -long-pair-of-wires, is mostly DC. It will be if 0.1 uF is large compared to the period (inverse frequency) at which this device is running.
The 1 uF cap on the Vin is there because I want Vin to be somewhat stable, even if it is being driven by bouncy switch connected to a stylus being lifted off and on from the GITD paper by someone doodling.
Anyway, that's what that's all about. The circuit built on the breadboard in the third pic, is the same circuit shown in the circuit diagram in Step 8, and the same circuit that goes into the finished product.
Step 12: Putting It All Together
The first picture here shows a virgin blue LED, side by side with one which has had its leads trimmed and shaped so that it can be pressed into the plastic shaft that used to be an ink cartridge.
The second pic shows what the shaft actually looks like: LED on one end, and a brass screw switch contact on the other end. The fine gauge (30 AWG) blue wires go to the LED. The switch contact, on the shaft, has an orange wire soldered to it.
The third picture shows some detail of what the other switch contact looks like.
The forth picture shows the AA battery holder, which has undergone a serious makeover too. Its been converted from a 2-cell AA holder, into just a 1-cell holder, and the empty space is being used to hold the LED-driver module and other components. Also visible in the forth picture are wiring connections to the light-emitting pen. These connections, insulated by masking tape, will be covered up by the pen's cap when in use.
The forth and fifth pictures show me testing the switch. Just a very small force against the LED/stylus is necessary to make it light up.
As described in Step 8, the force I am actually pushing against comes from a small section of the spring, which is always trying to pull the shaft forward, and open the switch.
Step 13: Take a Picture. It Will Last Longer.
Nothing lasts. Nothing lasts. Everything is changing... into something else...
I borrowed that line from Shpongle, and I think Shpongle borrowed it from Terence McKenna, but you know... it's true, more true for some things than others. Like this darned Phosphorescent Notepad: it's got more impermanence than one of those Buddhist sand paintings! Really, I think it may be just the thing for those who want to get some enlightenment in a hurry, if it actually works that way, but I'm not sure if it does.
But what if... What if there was some way to "save" a doodle from this glowing notepad, before it gets obliterated by entropy?
Well, judging from the title to this Step, there is a way to do this: simply take a picture of it. Some results of photographing these doodles are attached to this Step. Good thing too, because I hate it when I witness some marvelous phenomena, especially produced by some artifact I have built, but it's something my camera just can't deal with. It makes it harder to share with y'all on Instructables when I cannot show you pictures.
I said "simply" take a picture of it, and it almost is simple, almost. The camera has to be held still using a tripod. I also use a source of red light initially to help the camera get something for its automatic focus to focus on. Note that for reasons discussed earlier, red light does not kill the doodle. I also use the camera's countdown timer function so that my hands are free to doodle for ten seconds or so.
The setup for the photography is shown in the last picture for this Step.