Arlet wrote:
Careful with PC power supplies. They can deliver a lot of current, so one mistake on the board is enough to vaporize traces and components.
I can confirm that! They can deliver quite some fireworks
GARTHWILSON wrote:
but I still like to encourage good habits and neat work that will pay off when you get into the faster stuff.
I totally agree, you have to set a standard as high as possible.
I would really love to make Daryl’s SBC3 or similar. But frankly that’s too complex for me to start with.
You have to put yourself in amateurish beginners shoes. Those blogs swirling around the net show little steps with results. That’s what makes it attractive. It’s a big leap from having a simple breadboard setup running and your workbench computer, POC1.1 or SBC3.
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remember you can mix up the data lines to RAM, and you can mix up the address lines to SRAM
Yes, I learned about that possibility on building a VIC-20 memory expansion.
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Make sure you use the sections of a quad NAND
that’s an ongoing process, I use “delete” and “invoke” to select the right section. I discovered that not so long ago. It’s all learning by doing.
Checking everything by hand and even make your own parts library is indeed the best thing to do. For instance I used a VIA symbol I found on the net and luckily I discovered that VSS and VCC were swapped
. Even on EAGLE’s standard libraries a silly PNP transistor had E and C swapped.
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I have not done very much digital-only PCB layout, but I've done a lot of analog, up to 500 parts on a board; and packing it in by hand and routing it while I'm placing it, I get things so dense that basically you can't see the top surface of the board except at the edges. That's not possible if you just sprinkle the parts in and then set the autorouter to work. A human can always do a much better job than an autorouter. As for trace width, most PCB manufacturers don't start charging extra until you get down below .006". Even at .010", you can get two traces on the same layer between pads of DIP ICs.
That’s years of experience of course. And certainly of great value that you share that knowledge. But one can only show or tell about a skill, not hand it over to someone. And yes, autorouter sucks. But it’s tempting and sometimes useful for small sections I believe.