Glow In The Dark - display(a.k.a. "the YouTube counter")
The glow-in-the-dark clock is made from MDF, a PVC pipe with 1 stips of 5cm wide heavy duty glow-in-the-dark tape.
(banana for scale purposes only)
the moment I've made my morse code toy I
knew that this glow in the dark material was meant to be used for
So... I've decided to make something bigger... a display based on the same principle.
This time not with one white LED, but with many many more Ultra Violet LEDs. This because UV is simply much more efficient in transferring the energy into the glow in the dark material.
And considering I need 94 of these LEDs, wehich can be all active at the same time, efficiency is a bit of an issue.
Here on the left, you can watch a small video I made.
I demonstrate the functionality of this device (all the way at the end of the video). It is intended to be used as a youtube subscriber counter and clock.
Enjoy watching and don't forget to subscribe (when you do, don't forget to tick the little bell icon, to get a notification every time a new video is put online).
|It all started in 2015...
we've just bought a new cabinet. At that time the top shelf was completely free and had more then anough room for a large display or clock. The perfect place for my new glow-in-the-dark-tape-on-a-roll display. But if a made such a display, how large should it be, what should it be displaying. Ehmmm... considering that this is very similar to a classic dot-matrix LCD, I think it should be able to fit at least two lines. The most effecient way of charging the tape is by using UV-light. And UV LED's are cheap on ebay, so I bought a bag of 100. Knowing that I had this many LEDs available I calculated the a 16 char display was possible. The display area would be approx 50cm wide and using the peice of PVC pipe I had still laying around, it would be capable of fitting 2 lines. So I would be building a 2x16 char display, using LED's and glow in the dark tape. With 16 chars it would mean that I would require 96 LEDs, leaving me 4 spare LEDs... just in case. Well I can tell you know that that wasn't enough. Because of a silly mistake I fried some of the LEDs during a brightness experiment. So I needed to order another 100. But ordering things from ebay is tricky and so I ended up with LED's that were slightly different in light output and angle, but in the end I could compensate for that. So I you are intending to build this kind of thing and order from ebay... by double the components you need, just in case you need spares.
As I wanted to keep my options open I decided on LEDs in between the chars so that I could always decide to make it a graphic display with a variable font or whatever. So 96LEDs and a display of 50cm wide... plus some extra cm for endcaps, motor, bearings, etc. would soon lead to a total size of more then 65cm. Being 10cm tall, it is a pretty large display for only 2x16 characters. I decided to turn it into a clock combined with a youtube counter, just for fun. And hey... everybody needs a good clock,. might as well make it a non conventional one
the project began, I
started with great enthausiasm, made the LED
driver PCB's, programmed a microcontroller, doing the mechanics, and
wrapped 10 pieces of glow in the darkl tape around a 55cm long PVC
all went pretty smooth and quickly proved to be working pretty wel as a
display (works best in the dark). But there was one detail.
requires to display the correct time. And
I wanted this clock to be a perfect clock (low drift, easy to
configure, etc). So that could be an issue. Because I
could not make up my mind how to solve that problem (as simple as
possible), the project was put
aside... and we all know how that could end... in a permanently
Though the clock was never out of my mind as I kept it underneath my bed (for quick access in order to finish it). But because at daytime the display charged with ambient light it noticably glowed during the night. And because I used the heavy duty glow in the dark tape. The tape I used was designed/intended for use along stairways, or to mark exits. To indicate hazardous areas or safe passages in situations when the light suddenly fades. Imagine an exit in a bar somewhere, suddenly the lights go out, where is the exit, I can't see, it's dark. Then there is the opening of the door clearly marked by a mysterious green glow of the tape. Clearly visible and you can safely reach the exit. Wonderfull stuff. So being hevay duty tape, meant to be glowing for hours after being charged, I meant that it could be charged up so bright that you could read a book with it (well only for a few minites directly aftyer charging), you must be aware that brightness quickly fades to a much much lower level. But more then bright enough to remain very clearly visible at night.
So therefore you see the mysterious glowing pretty well at bedtime. With a roll of this underneath my bed (close along the edges) you can imagine that the glowing could be enough to keep you awake if you don't realize what's causing that mysterious green glow. A problem that was easily solved by a putting a towel over it. And so the half finished project remained under my bed, wrapped in a towel for a very long time. Before I knew it, the years went by.
roll itself is just a simple PVC pipe with endcaps. To one of those
endcaps (the right one in the photo) is a sprocket or gear or cog-wheel
(or whatever it is called these days) mounted. On both of the endcaps
there are some standard ball bearings to make it all spin very easily.
Just some ball bearing as using for skate wheels. Nothing fancy. The
whole gear system comes from a printer. On old matrix printer I had
salvaged parts from many many years ago. So it was nice that I could
finally use them in a project. It proved my right in saving it all
these years. The stepper motor is very small, which has an advantage
because this way I could fit in into the side of the cabinet. The motor
is indicated with red rectangle in the photo below. It is all very
very basic. As an axle I used a piece of threaded rod slightly longer
then the length of the PVC pipe. The pipe lays on this threaded rod
with the bearings. I used a thread rod for simplicity and to make sure
that both bearing were rotating along the same line. Making it less
wobbly then two small axels (one on each side). There is only
one tiny problem, the stepper motor has allmost no power, the gears
make it better, but still. Lowering the speed increases torque, which
is normal for a stepper but too slow would make it look bad.
Fortunately I could drive it fast enough to be acceptable.|
was march 2018 that I suddenly realized that I should all base
it on an
ESP8266. The last few years I've gained a lot of experience with this
piece of technology (a cheap module but
its possibillities and performance). So I removed the old
microcontroller and put in the new ESP8266 (an ESP-12E to be exact). I
ported the code I had to the ESP, modified some
existing code from the internet to monitor the youtube stats, re-used
some of my NTP code from
another ESP project. Funny though, for years I've been
pondering how to finish it. And
then suddenly BAM... inspiration... and with renewed energy it
was working like I wanted it to be in a weekend. Now the only thing I
needed to do was to make a nice enclosure for it, that took me another
weekend. And in the days in between I decided how it should look. I
decided that it had to look a little
like wood, to match the cabinet. But also to make it look a little like
an old radio, or at least not something like I made myself (because it
has to be nice to look at). Though considering my
woodworking skills and budget I decided to use some simple MDF and some
strips of wood bought from the hardware store.
Though first I hade to made my improvised mechaniscs a little sturdier. So I trew away the old base, which was nothing more then a crooked plank and used a straight piece of MDG. Which I painted mostly black on the placed were it could matter. The piece of plexiglass you see in the foto below, was one of the last things added to the design. As you can see the whole unit will slide in and out of the case easily. Fixing it with (perhaps a little too many) screws on the top... and bottom. So if I ever need to do some reapir to the mechanics, LED's or ESP I can easily reach all locations of the device.
|So I ended up making a simple rectangular box, screwed and glued it all together. Rounded the corners and edges using a plane and some sandpaper and glued on the wood strips. At first I wanted to stain the whole case with very dark coloured furniture wax. But that wasn't as nearly as dark and colourful as I imagined. Fortunately I tried it on a piece of scrap MDF first, so no harm was done. The I decided to use some stain and a large brush and even for the little effort I've needed to put in the staing process, it performed miracles. To get a little bit of darker coat, I stained it again a few days later. I was very pleased with the result. As the photo shows, the 2 pieces fit together perfectly. Akay... not perfect... more like a thight glove.|
|The end result is shown below. Here
you see the glow in the dark display acting like a youtube counter on
the top line (s=subscribers, V=views) to my youtube channel. And on
the bottom line there is the date and the time. The display is updated
every 30 seconds. Which is more then enough in the evenings. Regarding
the daytime, this kind of display is useless. Because the strenght of
daylight is so much that it completely overwhelmes the light output of
the glow in the dark characters. Meaning that the characters would only
be visible for a few seconds after being written. But is this a
problem, no not really. Mostly because the
clock is not really in active use... As there are 2 small
issues, first: the clock makes a slight humming noise each
time it updates. Not
loudly, but noticable when the house it completely silent (no TV or
radio), this is a problem for me personally and most likely a probelm
for the WAF. Second: the cabinet on which the clock was to be placed
isn't that empty any more as it was when I started the project 3 years
other words the situation in real life isn't completely as
in the picture below. When I started this project in 2015 the top and
most of the shelves were completely empty, but over the years all sort
of photos, "art" and "school projects" were placed on all the
shelfs. So eventually in 2018, there was no longer any room left for
the clock. But we agreed that I could make a
demonstration picture of my
project, so I could properly show it here on my website and after that
restore the contents of the cabinet back to normal. This way I
could show the whole clock as it was intended and I could mentally
file this project under the tab "finished".
ESP8266 is a great device, cheap but powerfull and a lot of examples
can be found if you program it using the Arduino programming
environment. So... that's what I used and it served me very well.
The code for the youtube stats is basically the code from Brian Lough slightly modified to my own taste. This code is very much used by youtube counters as featured on yuotube in combination with the ESP8266.
The code for the NTP server is worked on by many people, Michael Margolis, Tom Igoe, Ivan Grokhotkov and then modified to suit my own needs as I wanted NTP functionality, but didn't want a clock that spammed the NTP server. So I request the time... then sync my own internal clock to that time and periodically re-sync the clock to maintain accuracy.
In order for the code to run, you do need to supply your own API-key for youtube AND the youtube channel-ID. Also you need to fill in your own WIFI network SSID and KEY
|For those who are interested in the code
of my project, here it is
ESP8266_firmware.zip (the code for the ESP8266)
Schematics (the schematics for the controller and LED driver board (in my display I used 3 of these driver boards), there are no PCB layouts so you need to draw your own, but the whole design is simple enough to make on a piece of perfboard)
The code could be very much improved on to make it more user friendly to change the NTP server configuration, the wifi settings, the youtube details. Now that is all hardcoded into the firmware. But it would be more friendlier to do that via a webpage (being served by the ESP8266 itself). A nice programming exercise for the future (when the clock is put into real service).
this display is all for fun... though the materials used are
potentially memory elements. I used it to store light, but I could also
use it to store information. In the "good old days" they did this using
CRTs. Memories based on CRTs were called Williams tubes. Very
In esence, the fosforesence effect is used to store the information and therefore it doesn't really matter if you use an elektrontube or an LED to send energy into the material used for storage. Anyway, since storage is cheap these days it makes no sense to make such a memory based on glow-in-the-dark tape, some LEDs and some photoreceptors (with the proper circuit an LED could also be used to detect light). However, this kind of project would be completely useless today, but it could demonstrate the method of storage in a volatile media. How fun would it be to see this rotating roll storing data. Though there is one slight problem, the decay time is very long, so erasing data from this roll would be difficult or just take a long time. Although there are some videos going around that with the proper wavelength of IR-light you could darken areas of the glow-in-the-dark materials. But quick tests indicates that the tape I used was not reacting to IR-light at all. Therefore I expect this tape to have some sort of IR blocking coating but it could very much also be the case that I just used the wrong IR-leds or that I did not send enough IR light. Enough material to think about...