If I’m not using my drum machine with trigger out for the primary clock source I just use the LMNC EG on loop mode 
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Smart think’n. Wish I’d built the version with loop mode instead of the basic one 
I’m getting ready to order my first sequencer PCBs and it just occurred to me that I have the chassis of the potentiometers connected to the ground plane. I’m assuming this is okay, but I keep finding things don’t usually work the way I expect them to on my first attempt. Does anyone know if this would cause issues?
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Grounding the chassis is the right way to do it.
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You’ll still need to attach the pin of the pot to either a ground wire or the chassis (which in turn is attached to the ground of the circuit.)
Edit: im thinking full DIY version here. @eric is right. Carry on.
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For the potentiometer to function it is not necessary to ground its chassis. But it can not harm either. It may provide a bit of shielding, should that be necessary, but that should not be overestimated.
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It also helps with physical strength. Most of the time the PCB is only held with a few pots on the front panel.
I’ve seen first hand how the pins of the pots bend when disconnecting the power cable on my modules. And that can’t be good !
I didn’t solder these tabs because: -the modules aren’t “confirmed” working (so you may have to desolder a pot again if it’s the culprit, and desoldering these tabs must be a real pain), - my current iron is somewhat weak to solder them.
Soldering them is a must with this module design (maybe not if you have another means to hold the PCB on the panel), and grounding them is the logical way of doing it.
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Sorry, I’m a little lost here, what PCB are we talking about? Originally this topic was about the LMNC keyboard sequencer which has a stripboard for the Arduino and everything else is mounted to the panel. Has someone developed a PCB version?
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A few posts above @TayBae asks if grounding the pots chassis is the right thing to do before ordering his first set of PCBs (for some sequencer, I guess it’s LMNC’s one…).
Afriad I got lost too. Pics please
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Sorry for all the confusion. I wanted to get some experience going through the process of making a module from start to finish, so I started working on a sequencer that’s a mix of the LMNC and @analogoutput design. Anyway, here’s how it’s coming so far.
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fantastic pcb , I would buy one now.
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Thanks, glad you like it 
! I still want to test it to see if it actually works and then work on a faceplate. After that I’ll make sure to post the gerber files, BOM and whatnot.
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I find the pots and the corresponding switches to be very close to one another. You’ll have to use tiny knobs.
Try to move the bottom pots (and leds) up and the top switches down, should be easy with that huge empty space in the middle.
What is the cutout to the right for ?
I guess it’s 10cm high and will be mounted rotated 90º ? Did you make it a few millimeters smaller than 10cm so it will “cohabit peacefully” with the neighboring modules ?
Also, this kind of jack is twice as high as the 9mm pots. It won’t fit on a panel this way.
With a single jack, the easy way is to make another cutout there and wire the jack to the PCB.
(Otherwise you’ll have to make a “double decker” like most of LMNC’s modules)
Trigger count and pattern select have pots connected to the molex ? (maybe that’s the cutout ?)
Then why does pattern select have a 22K and trigger count a 100K ? Will the pots be of different values ? 50k and 10K maybe ? Why ? They only provide an analog voltage to the Nano, right ? If that’s the case just use the same for both.
Wouldn’t it make sense to insert a diode between pin3 of each step pots and GND to compensate for the output diode drop ? Or else the first 10% or so of travel of the pots won’t do anything.
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My guess is they’re rotary switches with resistors between terminals — that would account for the cutouts. But the 22k and 100k resistors, and the other resistors at the tops of the other inputs, could be eliminated by connecting not to +12 V but to VCC. Then you wouldn’t need these voltage dividers to keep the inputs under +5 V.
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Oh, I just noticed…
Only one output jack ?
You’ll need at least another one for trigger.
I bought some small knobs that should work but after looking at it more I’ll definitely be fixing the spacing issue on the next attempt.
The cutout on the right is for two rotary switches that’ll be used for pattern select and trigger count.
The dimensions are 17 x 10.9 mm so it’s fairly beefy, but a decent bit smaller than the LMNC version.
Mounted rotated 90 degrees??
Good catch on the jack, I like the idea of just making a cutout for it.
I don’t recall why pattern select and trigger count have different resistors
I think I meant to make both 100k but forgot to change it in the drawing.
Honestly though I like the approach @analogoutput mentioned with connecting
to VCC to avoid these resistors.
I meant, vertically in a 10cm wide module, with two columns of 4 pots… but if it’s 10.9cm…
Or are you doing a Eurorack version ?
Yes, @analogoutput 's proposal is the way to go in the next iteration. I was too focused on the values to notice that myself 
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Yea it’s a Eurorack version, but I figured I’d just make a larger faceplate if I ever wanted to use it in a Kosmo setup.
Also there’s no input jack because I want to program the Arduino to act as the trigger source.
That’s a trigger out you need.
Or else the rest of your modular doesn’t know when the note has changed.
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