As a spin-off project to my wall covering project I want to create an LED-Clock. The basic idea for the clock is a 7-segment digital clock gage where the segments are build up by multiple LEDs.
Contents
First Prototype
I ordered some stuff from an electronics shop including differently bright LEDs, and LED driver and a micro controller. I will publish a detailed plan later on when the board design is fix and working.
For the mounting plate I went into the DIY store and bought a tile of 50x90cm and 3mm thick acrylic glass. Not the expensive stuff as I wanted to experiment with it. I cut a 15cm stripe from the tile and drilled 3mm wide holes into it which didn’t go all the way through… so they are approx. 2mm in depth. Afterwards came the first test. I hot-glued some LEDs into the holes, two of each kind. Using a very basic wiring and soldering the LEDs illuminated. I put a sheet of paper in front of them to simulate the use-case. Well, the brightest LEDs are the winner… you can dim them later on by decreasing the voltage after all…
As the next step I created a simple 7-segment clock using inkscape, printed it and attached it to the mounting plate using tape. Then I drilled two holes for each segment through the paper and hot-glued LEDs into the holes. After some soldering action and micro controller programming mayhem (for which I want to thank Elm for his support) I was able to run a one-digit sample. And, computer scientist (read: “nerd”) that I am, I coded support for almost everything. Without testing it doesn’t make much sense but what the heck, right? Right!
I don’t have much to show at this stage but here is the first prototype. Yeah, it’s upside-down… my fault 
. To the right behind the plate is the board with the electronics (yellow-brownish).
Second Prototype
Pleased with the outcome of the first prototype I planned my next step: vamp the thing up to feature four digits and a colon for separation. This sounds so easy when I type it… But it does involve quite some action. First the electronics has to be redesigned to support four digits, holes need to be drilled and a lot of LEDs hot-glued to the board, the LEDs need to be wired to the board and finally the program can be tested.
This where I’m stuck right now. I started to make a layout for the PCB using eagle but I’m not done yet. Once I’m done laying out the PCB I can order the electronics stuff.
Ponoko
As for the mounting plate… I always wanted to design and create something using the ponoko store. It’s a very clever idea. Those guys give people the opportunity to design stuff, send it to them and they laser the design from sheets of user-defined material. Awesome! And this shop flashed back into my mind when I was… well… on the toilet.
It took me a day to create a design I was pleased with. And then… the shop didn’t allow me to upload it. It stated the “something was wrong with my design” but they “couldn’t quite put the finger on it”. Frustration! Half an hour later I tried a lot of things with my design but still no success. In a final attempt I tried uploading their own template… even this did not work! I was baffled.
Well, the next Monday I tried uploading the design from the university and it worked O_o. Anyway, my design combined with a 3mm thick sheet of acrylic glass should cost 120 Euros. I was a little shocked. Ok, I was prepared to pay quite a price… but wow, that’s a lot. And probably I have a tiny thing wrong in my design and have to make a do-over leaving me with twice the price…
I really want to try out ponoko tho… Maybe I can save some bucks by redesigning a little while still gaining experience with this way of “easily getting what I want, how I want it, and with high quality”.
Update July 29
I ordered a prototype from the German Ponoko partner called Formulor. Well, I decided to shrink the clock to a minimum size to save some money. It is now about 18x7cm and costs 52 Euros including shipping (which is a whopping 6,64… for a formerly 18x18cm piece of plastic…).
Also, I’m done with the Eagle layout of the electronics board. Although, I didn’t order the board and all the electronic parts yet. I want to have Elm take a look at it before. He knows quite some tricks and maybe I did something horribly wrong.
Next steps: Wait for the outcome of the laser-cut plastic; reassure that my board design is ok; order board and electronic parts. Sounds like a fun next week.
Update August 8th
Ok, I’m pretty satisfied with the outcome of the laser-cut plastics:
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The bad thing: the inlays don’t fit into the engravings even though I calculated for some extra space. I will use only the round edge inlays as spacers. Why? To give the light of the LEDs a little room to spread before hitting the engravings of the front plate.
Also, the electronic parts arrived and I soldered some LEDs together to get a feeling how it could look like when the work is finished. Well, I have to get it a little flatter I guess. But it’s ok. The LEDs fit nicely into the holes (which were designed so that the LEDs would pass entirely through, but that’s a different story.)
 LED Clock - Prototype 2 - Assembling - 1/4 |
 LED Clock - Prototype 2 - Assembling - 2/4 |
Still waiting for the PCB to arrive…
Update August 25th Second prototype: Done!
It looks pretty good.
Assembling the electronics was a tedious work, especially soldering the SMD parts onto the PCB. I accidentally created a few short circuits and it took me quite a while to find out where they were. That is probably due to me being a newbie concerning crafting electronics. Also, putting the 58 LEDs into place and wire them with the board was… well… tiresome. 
Here you can see how it looks like now:
 LED Clock - Prototype 2 - Assembling 3/4 |
 LED Clock - Prototype 2 - Assembling 4/4 |
The left picture shows the PCB in front and one digit hooked up to it. While the right shows the entire clock running. The protective foil is still on the acrylic glass which makes it a little blue.
I want to clean up the source code and reflect about it a little and then I will post all the documents here.