Grid Mark II

After completing the first version of the grid (see post a couple ago for complete details), I began pondering how awesome it would be to make a new version that had less spaghetti and fragility and was smaller with higher LED density, but had the same basic circuit design and components. The best way to do this was to make a printed circuit board. After doing some research on different options, I decided to try to make the PCB myself using the toner transfer method. The basic idea is to print the circuit on a laser printer onto glossy paper, then iron that onto a copper-covered substrate, then soak it in etchant to remove the copper not covered by the toner, then remove the toner and you have a PCB. Great and seemingly quite simple in theory. If you are looking into this method, I think it would work really well for small single sided boards. My board, however, is 5x8 inches (quite large) and double sided. If I ever did get one side correct, it would be ruined when I did the other side. Long story short, it was a failure. These are the best transfers that I ever got:

So, since DIYing it was out of the question, I looked into where I could get it made for less than a small fortune. Most places were well over $100 for a board of my size, but 4pcb.com has a deal for students where it is only ~$50 for a board including shipping. So, after re-doing my design in their application (wrangling all the wires to fit on 2 sides is not an easy task, and replicating it in a new application is no spring chicken) I ordered the board and crossed my fingers that I hadn't messed it up too badly, as this was my first foray into designing PCBs. A couple weeks later, and voila!

Gorgeous, yes? As an added benefit, ordering it meant that i didn't need to drill all 810 holes myself, and it was coated with a solder mask, which makes it more resilient to wear and tear. This board is actually 2 boards in one that needed to be split; the display is the square part that will hold all the LEDs, and the side board will stick off the back with a 90 degree connector to house the control chips. This means that it can theoretically be places side-by-side with more of it to make a larger overall screen. Future versions will likely contain this functionality. Nevertheless, after splitting the board (running a box cutter down the split 20 times per side or so and breaking it in half along the line), it was time to populate the board. It was at this point, however, that I discovered a mistake in my design that had been in it from the beginning. Without getting into too much specifics, I had switched 2 sets of 4 pins 3 times along the connection between the two boards. After having a minor freak-out, I managed to solve it by disconnecting 24 of the joints in the elbow connector and jumpering it together so the correct pins were connected. This is what the 3 juts of wire are off the side as you'll see. I also needed to re-write a bit of the multiplexing logic, but that only took a few minutes. After about 10 straight hours of soldering, I had myself a completed grid device. All told, there are 882 solder joints, 144 LEDs and 1 board of awesomeness.

Since I was making a new version of the board, I also decided to rewrite the controlling application to make it more user-friendly and include some more useful functionalities. This version adds the ability to dim lights, a large clock (the colon blinks on the second at 50% to 100% brightness) and the ability to display custom color images. To help make these (I had previously been doing it my manually creating a massive boolean array), I made an editor. There are still visualizations that cycle automatically and a marquise that can say whatever you'd like. Additionally, the app is backward-compatable with the old grid.

And now the money shots:

I would appreciate any comments or suggestions or ideas anyone has, new things are always good to add!