Personal protoboard design

DIY STUFF
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Motivated by some self-designed prototyping boards I’ve seen by folks here, @AriaSalvatrice for one, I was inspired to try my hand at designing my own. The following is my first finished beta sketch, and definitely has some issues I still haven’t worked out, but I’m liking where it’s going.

All the colors represent copper traces. Red is +V, green is -V, black is ground. I know it’s backwards but that’s what my brain tells me it should be and I just have to live with that. The orange is intended to be on the back copper layer. The components are mostly just for my reference.

Here are some details:

  • It’s two protoboards ganged together, which is probably obvious. One includes a spot for a 10-pin IDC header and other power components, along with dedicated space for an optional 78xx voltage regulator circuit and a small buss for the regulated voltage which can be bridged to one of the middle busses.
  • Two dedicated power busses for +/-12V from the eurorack connector. I’m probably going to set this up so that a trace can be bridged or broken in order to make it possible to put +V on both rails. There are two unconnected busses in the center IC “gutter” that can be bridged to ground and/or regulated voltage (or jumped to whatever else) if desired.
  • 1+3+4 holes on either side of the gutter all connected by default, which leaves six to work with when there’s an IC in the board, with a thin trace for cutting to 1, 3, 3. I found myself needing just one more hole all too often, so I put in the extras here.
  • The single pads on the edges of the boards are for passing signals from board to board via pin headers. Also useful for jumping a signal to another row without “spending” a hole closer to the chip.
  • The black squares/rectangles were mostly for my reference while laying this out—they represent space to place pin headers for sending power between stacked boards. I was having trouble finding space on my power busses for headers on my Electrocookie protoboards, so this solves that.

Issues to address:

  • I don’t like the inelegant routing of the ground trace in the upper left where it goes from the IDC header under the lead of that PTC fuse to the left ground buss. I’m considering using a ground plane layer just to increase its availability across the board. Alternatively, routing it on the back as well.
  • I’m not sure if thin traces designed to be broken are a good idea on a power buss, even if it’s ground.
  • I want to be able to use SMD decoupling caps soldered behind the ICs (on the back of the board), so I need to make sure the spacing works for that.
  • I’m probably going to run the ground traces on the back of the board, mirroring the front. Same with the “generic” pads.
  • I think I want to make use of plated vias in some places for passing signals around back to front (like on the 1 hole pads, and the power connector), but can probably use a bit of wire soldered through on both sides to the same effect, mostly.
  • I’m trying to keep the “parts part” of the board to the 2.54mm pitch standard for THT parts, but I’m sure there are places where I don’t actually need to do that.

This ran way longer than I expected, and hopefully it makes sense. I’m totally open to suggestions and feedback. Thanks!

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I made some changes and I think I fixed a few of the problems I was having with my design so far. Beta 2, I suppose. Next step is throwing it into Kicad and figuring out how to use the board editor.

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Just to say a few words about my design choices:

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  • Through hole diodes and capacitors, because I didn’t want to mess with SMD. If I were doing it over again I might use SMD diodes. Maybe not the caps though, they aren’t that much smaller and I find them a pain to solder. Actually I did come up with a version with surface mount parts, but for some reason it was the caps and not the diodes, and it added LEDs with resistors as power indicators. I don’t know why I thought those were good ideas.

  • If I were doing it over again I might just have one +12 V bus at the top and one -12 V bus at the bottom, in favor of either a narrower board or more holes per row. Or maybe not. Having both buses on both sides gives you the freedom to orient ICs either way easily.

  • I definitely wanted to keep it within the cheap PCB size range; the prime number of rows is because that’s how many fit in a 100 mm long board. The 55 mm width is harder to justify. It’s just a little too wide to go parallel behind a 50 mm Kosmo panel. I suppose squeezing it down to 45 mm would be difficult even if there were only two buses per edge, unless you got rid of two other things I wouldn’t want to get rid of:

  • Numbered rows (and lettered columns). Without these it’s very easy to make mistakes going from a design to a built circuit.

  • Mounting holes.

  • I also drew up a version with footprints for two 1/4" jacks, but I’ve never felt a need to get those fabbed.

Repo here: GitHub - holmesrichards/Protoboard: Eurorack/Kosmo powered prototyping boards

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Thanks for the comments. I haven’t looked at the “cheap PCB” sizes, so it’s good to know that 100mm is the target. I decided to run one rail on each side, plus ground, and set it up so it’s pretty straightforward to leave off the PTC on the negative side of the IDC header and jump +12V onto both rails when I find I dont need the negative voltage. The main complaints I’ve had with the protoboards I’ve been using is that they’re not quite wide enough and not quite long enough, so I’ve done these 7 wide on each side, and 35 rows. Using traces and SMT parts would save space at the top, though it would mean losing flexibility if I’m not soldering them myself. I definitely need to get this into Kicad so I can make it fit into reality a little better. Any suggestions for doing traces like this when they’re not between components?

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At JLCPCB for instance, boards under 100 mm x 100 mm are a “special price” of 5 for $2 for the first one in your order and 5 for $4 for the other ones. Or I think 10 for $5. For boards over that size, or for 15 or more, you pay an “engineering fee” plus a price per square cm. Which for very small boards turns out to be cheaper for 15 of them than the “special price” for 10! But for boards near 100x100, it’s definitely cheaper under than over. (Actually I think the threshold is a bit over 100x100.) Other Chinese companies often have similar deals.

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