Mastodawn

Lykso Nov 19

Looks like I'm going for it.

This is rough. I've forgotten a lot, and I didn't know much to start with.

After a couple rewires, my perfboard is missing quite a few copper pads. Some of the components are attached only to each other, not the board. I wonder if epoxy would be sufficient to hold them in place.

This project quickly went from being one of my cleanest perfboard prototypes to one of my messiest. All because I decided I wasn't *actually* comfortable with cutting the corner I was cutting.

Less-recent self: "I can skip the resistors for the LEDs, right? They're salvaged, they'll be blinking on and off anyway, and I only have them on here in the first place because these jacks can't fit in 2hp and I didn't like having all that unused space when I went to 4hp. Plus it'll be interesting to see how it works out, right? Yes. I will leave them off For Science! "

More-recent self: "Why did I wire these up like this? This is Wrong and Embarrassing. I must correct this IMMEDIATELY."

There are two wolves inside me. One cares so little about correctness that they must never be let near a soldering iron or production code. The other will bootstrap their own Linux on the only fully open source hardware available at the time just for the assurance that everything is Correct. When they fight, the perfboard loses copper.

I also momentarily got Ohm's Law reversed somehow and spent a minute thinking I'd have to put the LEDs in serial with the shift register pins when I'd already soldered them in parallel, but fortunately I got my head on straight again before any perfboard was harmed.

No shorts. Gonna design and print a plate before applying epoxy because the board is a little curved and it definitely won't be happy about bending at all once it's epoxied up.

Lykso Nov 22

No epoxy yet because I don't have proper PPE for that shit at the moment, and won't until December 3rd at the earliest. Still gonna wire it all up and test it out a bit. Here's a progress photo.

Hope I don't fry anything!

Lykso

Nothing caught on fire or blew up, but the module also isn't working. Debugging will have to wait until tomorrow, I guess.

I've figured out the problem and I'm not sure how this design made it off the breadboard. I thought it was working poorly because of loose connections; it was working *at all* because of loose connections!

There's enough room left on the perfboard to correct my mistakes, I think.

Well. I modified the perfboard prototype, but still no luck.

Problem had been that the serial clock needed to be the inverse of the register clock for my serial-in, parallel-out shift register to behave like a serial-in, serial-out register. Breadboard prototype had been unstable enough that it kinda worked with them just tied together.

Fails differently now, but still fails. Back to the multimeter.

Huh. There is a short between pins 10 and 11, but only when there is a power cable plugged in.

It does not matter if the power cable is plugged into anything on the other end.

This is a mechanical problem.

I've made sure, with soldering iron and hobby knife, that the solder traces between those two pins are well-separated. I am beginning to suspect the chip socket. 😛

Chip socket seems to be fine. No signs of melting, and the power header pushes on other nearby wires and components, but not that. No obvious route from those wires and components to a short, but this perfboard is a mess. Used Dupont headers as an extender for the power cable to power it up without creating the short successfully, but still no dice. Gate inverting transistor isn't damaged, but I'm still not seeing what I should be from it.

Maybe I'll set this project aside for a bit. My workspace is a disaster and the housework's getting neglected again. I should make an actual schematic in the meantime. Most likely I'm going to have to discard the current perfboard mess. I don't have high hopes regarding my ability to salvage something workable from this at the moment.

Probably time to get some sleep, too.

http://lyk.so/eurorack/shift-register/schematic.pdf

Right. Using PCBs seems to be popular. I'm not an electrical engineer by training. Here's the schematic I've come up with. Anyone feel like taking a peek?

Gonna start designing a board with this schematic and see where that lands me.

#synthdiy #eurorack

Lykso Nov 25

I've designed a board, sent off for fabrication, and... within less than 12 hours learned enough to realize my circuit has some big flaws that, while they won't keep the module from functioning, aren't the sort of thing I'd personally like to have in my eurorack. So I've canceled the fabrication order and am back to the drawing board, this time with a slightly better understanding of what I'm doing!

Lykso Nov 25

In the meantime I've set up a website where I might, in the future, sell a couple copies of my modules to defray my parts and fabrication costs, provided I can come up with something that seems sound enough.

http://eggmodular.com

Egg Modular

Lykso Nov 26

Continuing to work on the circuit design. I think, once again, I've arrived at something that works which also addresses the previous design's deficiencies. I am using an op amp for the first time, because buffered outputs are important!

Still unsure of whether to use 8V or 5V gates, but leaning toward 5V just to keep things simple. If it's good enough for ALM, it's good enough for me, right?

Considering learning to hand-solder surface mount parts in order to make designing the new PCB easier.

https://www.falstad.com/circuit/

Lykso Nov 26

This browser-based circuit simulator has been very helpful for testing out basic concepts. Transistors and op amps are still shaky territory for me, it seems.

Circuit Simulator Applet

http://lyk.so/eurorack/shift-register/schematic.pdf

Lykso Nov 27

New schematic dropped. Old schematic had really obvious, embarrassing errors. New schematic (probably) has less obvious, less embarrassing errors!

I would be shocked if it has *no* errors, but I'd be okay with being shocked in this particular case. 😸

Lykso Nov 29

I now have 9 bypass capacitors on this board. I think this may be overkill, but I'm erring on the side of overbuilding because I really kinda don't know what I'm doing yet.

3 for +12V, 3 for -12V, and 3 for 5V.

Lykso Nov 29

I think the design is as good as I can manage at my current level of knowledge. Just updated the schematic at http://lyk.so/eurorack/shift-register/schematic.pdf and sent off for PCB fabrication.

Lykso Nov 30

PCB fabrication paused again as I've had a change of heart regarding using the 5V rail.

Lykso Dec 1

Further meditation on the schematic has revealed more problems. At least I'm learning a lot.

Lykso Dec 3

I think my problems have gone from "this mistake could destroy something" to "I'm not sure if this design element is actually doing exactly the right thing," which is nice.

Lykso Dec 8

I went and asked people on the Internet for a review of the schematic I could not find anything wrong with and now I have a completely different schematic which I am still working on. I'm glad I asked. Even though my original schematic would have worked, what I've got now is more elegant and has a wider output voltage range.

Lykso Dec 12

Turns out that my design cannot work unless I also design and manufacture my own audio jacks. I'm a few days into that now. The only tools and materials on hand which seem applicable to the problem are my FDM 3D printer, wire cutters, needle nose pliers, and paperclips. I've gotten close to something working, but no dice yet. Ruled out two general approaches and am currently printing the first version of a third design.