Tuesday, October 25, 2011


This last weekend we soldered together a simple little 8 X 8 grid of LEDs. This took 2-3 people, while soldering it together and checking it over, about 2.5 hours to do. This can give us a great baseline for about how long it should take us to assemble the cube. Basically, about half an hour to forty-five minutes per 4 X 4 square, including checking it over for any problem connections. Assuming that we can take the same times to produce the other 8 remaining 8 X 8 cube segments, we could be done with soldering this term's goal of a single panel in about 20 more hours. I feel like the guides printed out helped to smooth assembly along greatly, and ensure that each LED is consistent with every other one.

The above LEDs are set at 5/8" intervals, meaning that also the space between panels will need to be about 5/8". This spacing can give us an estimate that the cube of LEDs, not accounting for any of the controlling wires, will be about 15 inches on a side. Once concern with the smaller spacing is that the PCBs that I am trying to design need to be less than 5/8ths inch tall, or there will be some interference between layers. My biggest concern height-wise is the TIP31As, as these are through-hole transistors. Everything else should be fine at its current height.

I haven't made any more progress towards completing software. I know as of right now that I am getting some weird behavior regarding the GSCLK signal. I presently have a high frequency (much higher than I anticipated by a factor of 4-6) and I am not getting a consistent pulse going from 0V to 3.3V. That high frequency is something like 1.5V. I have 2 possible ideas for solutions:
  1. Implement the timers to control when the PWM toggles on and off.
  2. Change the writes from PORTESET to LATESET. That way I am changing the latch as opposed to the port. I am hoping that implementing this will fix the problem, but I still also do need to take care of the PWM timer as well.
I have also finished up the BoM, aside from confirming item counts. Now that I have that, I am working on trying to get the PCBs completed and sent in for manufacturing. It looks like I can fairly easily design the PCB to fit in an "L" shape, meaning that outside of the LEDs on a panel, I would only need a few inches of room to spare on a couple of sides for handling the PCB. As stated above, the TIP31A's height is a concern, and I may have top cut out a small hole in the lexan of the above layer to account for this height. I am hoping that I can get the landing holes of the transistors cut a bit wider around to accommodate for the extra width that the transistors have on part of the leads.

No comments:

Post a Comment