Wi-Fi Controlled Open Scoreboard

Progress is slow. Currently decided to swith the driver design to use an optocoupler since I was going to use transistors to drive the FET gates anyways. Isolating the power from the logic probably isn't needed but couldn't hurt, and males the board more version's for other uses. 

Little progress to report since last log. Waiting on the power board to come in.  I want to finish the design for the other boards before I order parts from digikey, so I can get them all in one shot.  The plan for now: 

1. get the board layouts finished.

2. Order parts. 

3. Design and print the 7 segment digits.

4. Design the front panel. 

5. Assemble and test boards.

6. Rework  

Well I managed to battle my way through KiCad and got the 3.3v power board out to Oshpark.  I'm doing about 4 modular boards to ease testing and risk since I'm not very experienced.  However I did learn that I was already out of the running for the prize.  So bummer on that. I guess I'll see if I can make my project better than some of those out of good old fashion spite. Oh well, on to the next board, got to get the prototype going so I can start programming. Wrestling season is right around the corner of I actually want to use this thing.

Well, between family fun time and battling KiCad, I didn't quite hit my goal. I managed to separate the power supply circuit to a separate project and am in progress of laying out the board. KiCad has been a challenge for me, as this is my first project with it. Although i have only done one other board ever, it was done in Eagle, and I have to say it was much easier. The point I gave up yesterday was when I realized the netlist was screwed up and it was having me route pins that clearly were not connected to any thing in the schematic. I'll try tonight to sort out that madness so I can get some parts on order. I have a project in the back of my head to write programming language for this stuff instead of drawing it and using r. That might be my next project.

Just added a word document of project specifications to the GitHub. This is meant to be a governing document for the project. It's organize as an indented list such that as the project progresses additional information can be added under each item. This will provide a summarized collection of design decisions and specifications, as well as place to keep detailed information and calculations.  

I'm currently bouncing around in the back of a minivan on my way to Indiana, and although I want to work on PCB stuff, I found it nearly impossible to work KiCad with the touchpad. So I decided to work on documentation instead. This was a MS Word document, but I think OpenOffice can open docx files, so I think this is open. Let me know if you want it in a different format.

I'm contemplating the best CAD program to use for the physical design (both 2d and 3D). I'm thinking I'll need some basic 2d drawings for the display layout, and 3D for printing out frames for the 7 segment digits. Finding free/open CAD has been a challenge in the past. I just can't find anything that I find easy to use. If all else fails I'll probably end up using the Autodesks 123D for modeling, not sure for 2D.

On a similar note, and in the spirit of openess, I'll have to download OpenOffice so I can document in a shareable format.

Goals for the weekend are, 

1. Get one PCB layout done and on order. I'm thinking the power supply since that is the smallest and should be easy to test. 

2. Physical design of the 7 segment display pieces. I'm thinking of a nice plastic holder to place the LEDs in that can be easily attached to a panel of some sort.

3. Stretch goal, complete a second PCB layout. The LED drive would be good because that is also small and easy to test out of system.

Edit: CAD links to check later.

http://www.doublecad.com/DoubleCAD/DoubleCAD-XT-v5

http://www.3ds.com/products-services/draftsight/overview/

http://nanocad.com/page/FAQ (*free with registration required)

Doing some simple review/research. Good to do when you don't do this stuff for a living.

I've also made the design decision to make the LED power drive into its own reusable board. I will use a latching shift register to take make a 3 pin interface, allowing me to use a smaller cheaper package for the FPGA with less pins. Plus since this is just going to be switching a DC source for the LED strips, it could be used in future projects. I'll build it with 16 high side outputs and 16 low side outputs, which will cover all my LED segments with room to spare.

http://www.electronics-tutorials.ws/transistor/tran_7.html

http://www.electronics-tutorials.ws/transistor/tran_4.html

http://www.edaboard.com/thread253098.html

I did some more work on the schematic, and committed some changes. I worked on splitting it up into separate sheets, and started on the LED drive.

I updated the System overview diagram in the project description, so It would look cleaner than the hand drawn one. I also added this file to the GitHub. 

I used the following to create the diagram, 

http://sourceforge.net/projects/dia-installer/?source=typ_redirect

Just doing some quick math to see the current requirements of the LED display. The LED strips I have are made for 12v and have a built in resistor. They are separated into groups of 3 serial connected LEDs with the strip itself all in parallel. There are exposed copper pads on a 5CM pitch, where the strip can be cut. 

When connected to a 12V source the entire red strip pulled roughly 1.43A. The green pulled 1.3A. The strip is labeled as 5M with 60 LED per meter. That's 300 LED total and 100 total 3 LED groups. That gives 14.3mA per LED group. I figure for the 7 segment style display, 2 5cm segments would give 20cm x 10cm digits, which should be pretty visible from a distance. That's two groups per segment for about 28.6mA per segment. That will be the bear minimum required to drive each segment. 

Assuming I allow for 13 digits (time (4), score(green/red)(4), team score(green/red)(4), and period (1)), I can drive the display as a 7 x 13 matrix. This give a potential for 13 Segments on in parallel for the current source, and 7 for the current drain. That give a minimum of 371.8mA per output to drive the display. 

My switches I have chosen look like they can handle these requirements. 

http://www.irf.com/product-info/datasheets/data/irlml2060pbf.pdf