Now that I've prototyped a large shift register on my breadboard, I've decided to make a PCB version of the board for use on my model railroad.
I'm going to construct this as 3x16 bit I/O cards that can be daisy chained together to give me a total of 48 bits of digital I/O.
I'll be creating the cards so that I can easily add different output modules - some with ULN2803's for smaller devices <0.5A current, some with 60A MOSFETS for serious loads.
In order to test the system, I have made some simple 8 bit LED display boards which will plug into the shift register board as a test harness. I've made these so that they can easily be used in a breadboard as well.
The reason I've made these first is that they are very low risk. I designed them using the freeware version of Eagle from CadSoft.
The PCBs were easy to design after watching the YouTube tutorials - plenty available. I uploaded my PCB design to SeeedStudio and got my boards back in about 10 days.
As you can see, I'm allowing a total of 8 lines plus power and ground in to my LED Debug Board. I've also included a single LED to indicate power so that you can tell that things are actually working.
The schematic appears below:
And the PCB layout is here:
After about 10 days, I got my boards:
And here it is fully populated - worked first go!
