IN-14 Nixie Clock Mainboard (4 stages)
Back to this stuff again - this will be the main circuit board for my wife's nixie clock. It will hold the microcontroller, the real-time clock chip and backup battery, and the high-voltage power supply for the tubes.
What you see here are the four steps of preparing the board. Upper left, the bare copper board with the design for the bottom side of the board ironed on. Laminated on, really, since I use a laminator instead of an iron, but "ironed on" sounds better and reminds me of those little patches you used to get in cereal boxes. Upper right, the board after being etched (so the top layer now shows through). Lower left, the Lovely Shiny Copper phase after the toner has been scrubbed off. Lower right, tinplated and ready for drilling and cutting.
This time I tried a different circuit board layout program - Cadsoft's Eagle (free version). It's nice, though its interface is weird and it is limited in the size of board it lets you make. The limitation was not so strict I couldn't get this one done, though. Yay!
I had been using ExpressPCB's layout software, which is slick and unlimited in board size, but Eagle has two advantages: one, it can do automatic trace routing, and two, it isn't specifically designed to not let you make your own boards so it's much easier to get actual-size board imagery from it. These two things probably saved me a week of hobby time on this project even though I had to learn a whole new software package.
The autorouting really is nifty - you lay out your circuit as a schematic diagram, then you can create a board from that. The board initially looks like a blank rectangle with all the parts sitting next to it, the electrical connections in place but represented as straight lines so they all cross over each other. You lay the parts out on the board in what you guess is a good arrangement, subject to requirements like needing the power connector to be in a certain place and so on. Then you invoke the autorouter, which figures out how to make all the connections so that they get where they need to go and don't touch one another. This is pretty impressive - it's a low-level Artificial Intelligence problem, akin to (say) coming up with a delivery itinerary for several dozen pizza boys bringing pizzas to a bunch of different houses simultaneously, so that they reach everywhere in the shortest amount of time possible and without crossing each other's paths. As an AI researcher, I have enough professional egotism to think I could write a better one - but since they've saved me the trouble, I'm happy enough to use theirs.
Even better, you can tweak the autorouter's behavior to make its designs friendly to homebrew circuit board production. I attempted that for this board and I think it'll work. I need some practice before the boards I make are elegant - this one has some signals traveling a lot further than they really need to, but it should all work.
I added the hatch-filled areas in Paint Shop Pro as a postprocessing step. I wanted to save etchant - which you can do by filling the big blank areas. At the same time, I didn't want to run my printer out of toner, so I used a hatch fill instead of a solid fill. It seems to have struck a good balance.
IN-14 Nixie Clock Mainboard (4 stages)
Back to this stuff again - this will be the main circuit board for my wife's nixie clock. It will hold the microcontroller, the real-time clock chip and backup battery, and the high-voltage power supply for the tubes.
What you see here are the four steps of preparing the board. Upper left, the bare copper board with the design for the bottom side of the board ironed on. Laminated on, really, since I use a laminator instead of an iron, but "ironed on" sounds better and reminds me of those little patches you used to get in cereal boxes. Upper right, the board after being etched (so the top layer now shows through). Lower left, the Lovely Shiny Copper phase after the toner has been scrubbed off. Lower right, tinplated and ready for drilling and cutting.
This time I tried a different circuit board layout program - Cadsoft's Eagle (free version). It's nice, though its interface is weird and it is limited in the size of board it lets you make. The limitation was not so strict I couldn't get this one done, though. Yay!
I had been using ExpressPCB's layout software, which is slick and unlimited in board size, but Eagle has two advantages: one, it can do automatic trace routing, and two, it isn't specifically designed to not let you make your own boards so it's much easier to get actual-size board imagery from it. These two things probably saved me a week of hobby time on this project even though I had to learn a whole new software package.
The autorouting really is nifty - you lay out your circuit as a schematic diagram, then you can create a board from that. The board initially looks like a blank rectangle with all the parts sitting next to it, the electrical connections in place but represented as straight lines so they all cross over each other. You lay the parts out on the board in what you guess is a good arrangement, subject to requirements like needing the power connector to be in a certain place and so on. Then you invoke the autorouter, which figures out how to make all the connections so that they get where they need to go and don't touch one another. This is pretty impressive - it's a low-level Artificial Intelligence problem, akin to (say) coming up with a delivery itinerary for several dozen pizza boys bringing pizzas to a bunch of different houses simultaneously, so that they reach everywhere in the shortest amount of time possible and without crossing each other's paths. As an AI researcher, I have enough professional egotism to think I could write a better one - but since they've saved me the trouble, I'm happy enough to use theirs.
Even better, you can tweak the autorouter's behavior to make its designs friendly to homebrew circuit board production. I attempted that for this board and I think it'll work. I need some practice before the boards I make are elegant - this one has some signals traveling a lot further than they really need to, but it should all work.
I added the hatch-filled areas in Paint Shop Pro as a postprocessing step. I wanted to save etchant - which you can do by filling the big blank areas. At the same time, I didn't want to run my printer out of toner, so I used a hatch fill instead of a solid fill. It seems to have struck a good balance.