I've made synth protoboards for Kosmo & Eurorack, care to review my first real hardware release?

KOSMO MODULES
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So, I had some of @analogoutput’s protoboards printed, and they’re cool right? But I’m cheap as hell and I thought I could stack up two of those bad boys to gull the fab into giving me ten for the price of five.

Plus in addition to being cheap, I’m lazy, so I wanted a different configuration of power rails that cuts down on wiring.

Behold:

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And it’s designed so you can do this:

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Revision 1 had minor issues (mostly in the silkscreen), so I made a revision 2, I’m 99% sure it will work just fine but I had to remake some traces (I removed the 4mm space in the center).

This is my first real hardware release intended for use by others: care to take a look and tell me what you think? Not just the board design itself, but also the docs. I want my stuff to be as user-friendly and foolproof as possible.

I might not take immediate action on your feedback, but it will probably be useful for future projects.

And if you feel like gambling a whole 7 of your hard-earned currencies, maybe you’ll want to try out having some printed, at your own risk?

Note that the CC-BY-NC-SA license is a deliberate choice that was not made out of a lack of education about what it entails. I will not debate or negotiate it.

Okies, enough preamble, here’s the stuff:

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Just my two cents (may not be worth even that).

  • Why not highlight multiple of 5 instead of numbers congruent to 1 modulo 5?
  • Why not have a V-score or slot to help separation of the two boards?
  • It seems to me that the gaps for solder bridges could be narrower.
  • I’d maintain the 100mil spacing of holes everywhere, including in the gap bellow ICs. You could put two busses shortable by solder bridge.
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Once you add a V-score to a small order, they bump up the price such that it’s just as expensive as buying double the amount, maybe even more. I also expect half of the boards will be used intact, a V-score would not let me run the power and a few traces between halves.

Also, there’s definitely room for two rows in the center, but I wanted to have the ground easily available to both pad groups.

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Revision 2 of my protoboards are here! Looking perfect, but I haven’t tested them yet, just checked continuity.

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Revision 1 was already working well but had some mistakes on the silkscreen so I wanted to order version 2 to confirm it’s safe to have yours printed. The files on the github repo are for that revision, i’ll update it soon with ready-to-use gerbers and updated photos.

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nice and interested , very cool so far , great strides good job

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Looks good, could share the price for this ?
I am using the ones from ElectroCookie, they are not cheap but the quality is really good (in terms resistance to heat, desoldering, etc…)

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It costs me €7 for 5 boards with JLC. I go with them because they’re the only budget fab that takes care of european import duties.

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Ok thanks. That’s actually a lot cheaper than I anticipated… damn it, I might have to try this as well…

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Ah, the old trick of running a decoy trace from one board to another to fool the people at the factory thinking that its a single board. I never thought this would actually work. Well done! I wish I’ve seen this before I sent my last order.

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JLCPCB explicitly says it’s allowed now! But only for small order I assume. The page is in poor english, so it’s a bit unclear, but if they refuse a board for having multiple designs, it might be worth pointing out this page to ask the reviewer to reconsider:

https://jlcpcb.com/quote/pcbOrderFaq/Different%20Design%20in%20Panel

(but also — i absolutely expect some of these boards to be used uncut! 30 rows just isn’t enough to fit some projects)

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Yes, just read that on your github page. Sweet! By the way, I was wondering. Is there a reason why we need to stick to the 10 pin IDC connector for the power rails? I find those ribbon cables are quite pricey and seen other people use the much cheaper/smaller/convenient 3 pin JST connectors in their DIY builds and PCB designs.

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I’m no expert on that, but it seems almost everyone agrees it’s a pretty bad standard. If I knew more about electronics and didn’t care to share plans I’d totally do my own thing — simpler connectors, Banana jacks, etc. But there’s no displacing entrenched standards

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I pay nearly the same amount per meter for 10 conductor ribbon cable as for 3 meters of hookup wire. IDC connectors go for more than JST, though, I guess. Not that they’re anywhere close to the highest price parts of a build. And I find ribbon cables faster and less aggravating to make than Molex or presumably JST.

I don’t think ribbon cable is a terrible standard, but it’s not that great either. If I were starting from scratch and if I were solely building my own designs for my own use I’d probably use something like JST. I do like to sometimes use Eurorack PCBs or other people’s Kosmo PCBs, though, and I like being able to sell or trade my extra PCBs to other people, so for me it makes sense to stick with the ribbon cables.

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Thank you for your input. I haven’t thought about making my own ribbon cables, that could be interesting… To give some context, a 20cm ribbon cable with connectors on either side retails for 1.20 in the shop where I buy locally, with no option for discounts when buying bulk. The equivalent 20cm JST PH retails for only 20c and they will sell for 16c when you buy 10 of them. When 6.35mm jacks sell for 16c, potentiometers for 20-40c, knobs for 25c, and genuine CMOS chips for around 40-90c (all local storefront prices including a hefty VAT, properly packed, no ebay/amazon questionable sellers), I was scratching my head why I had to pay that 1.20 for that ugly bulky cable! Also interestingly, that 16c JST cable has only a connector on one side, but I can solder the other side directly on the veroboard and with the color coding that it has on the wires I can’t go wrong with plugging it the wrong way. I have to double check on each side of the IDC cable though!

I totally understand the argument about sharing/trading modules/pcbs though.

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I’ve made my own ribbon cables for some time now, after finding online sources out of stock too often (and I didn’t have a local store selling them). At Tayda the connectors are 20¢ each. Using box headers prevents plugging in backwards, provided of course you soldered the header and crimped the connectors the right way! Making my own cables also means I can cut each to the length I need whether it’s a “standard” length or not.

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As long as you get the orientation of the connectors and cable right,

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(note, I’m using the 16 pin variant and the connectors are shown prior to adding the guards)

you can make usefull cables at home on a budget using a vise or some pliers to crimp the connectors. I’ve made lots and lots of cables so far and have been using them after running them all through a DIY cable tester without any problems so far…

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Same here, I am doing mine manually, it ends up being real cheap. I got scared at some point when i read about this cable tester, it never occured that it could go wrong

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The cable tester is just a way to make sure that there are no shorts.

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Can’t I just use my multimeter instead of a specialized device? I am routinely checking all the connections in everything I put together anyway.

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You can, but there are 10 conductors to check for continuity one end to the other, and against 9 other conductors for shorts, and that gets old fast. Putting together a $2 device to check everything at once is a big time and annoyance saver.