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Max PCB height for Eurorack?
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Author Max PCB height for Eurorack?
AlX0298
Can someone help me determine the maximum PCB height I should design to for a Eurorack module?

The limitation is the rail thickness. It seems to vary from one case to another. But Ive never heard of module not fitting into a case, so there must be a measurement. I know the holes are 122.5 mm apart and the holes are 3.2 mm diameter. But the PCB behind the panel must be smaller so it does not sit between the rail and the panel. So what is the maximum PCB height.

See attached picture for details.

Thank you!

lasesentaysiete
I would aim for 100mm but someone with actual experience might suggest a more precise number.
flts
i googled "pcb height eurorack" (without the quotation marks) and it provided several good resources. the first hit produces several results from this very forum, and the second one is an image about one particular person's rule of thumb for his designs.

edit: so i wouldn't sound rude / unhelpful, depending on person who's done the measurements and how careful (s)he is, you will find people recommend anything from 106mm to a bit under 110mm as the maximum pcb height to aim for. there is also the point that a lot of pcb fabs have cheap deals on pcbs 10x10cm or under, so a lot of people, especially diyers, simply tend to use 100mm high pcbs for cost / convenience reasons.

in any case, i suggest checking the discussions about the subject if you are unsure about what works in your situation.
Boogie
AlX0298

The height I (Nabla-Instruments' MiniP7, MP7, Clap'a'Trap, ...) am using is set to 110mm.
AlX0298
This is very helpful, thank you!
av500
allow 9mm clearance on both sides, so 128.5 - 18 = 110.5mm
Jarno
+1

In practice, I use 100mm, mostly because of cheapness of PCB's in China.
cackland
110mm here, had no issues.
JohnLRice
Also make sure that no components overhang the PCB height. Like for instance if you use a non-shrouded power header, take into account that the connector on the cable is wider and will extend past the edge of the PCB if the header is too close to the bottom etc.
ersatzplanet
I make my boards 0.4" (10.16mm) from the front panel tops and bottoms. Never have had a complaint yet.
mskala
My guideline is 110mm max; in practice I think the biggest I've gone has been 108mm. As others have said, 100mm will often get you a better price from Chinese PCB prototyping houses, but that's less likely to make a difference when you're buying larger numbers of boards.
AlX0298
Thank you all for the good advice! Looks like I'll use 110 mm to start and try to minimize.

Why isn't this standardized though? ay500 said 9mm clearance, is that a standard or just experience like others have had? I just seems pretty bizarre that this isn't a standard measurement, where if you mess it up, the module won't fit in a case. Although I've never head of that happening.
flts
AlX0298 wrote:
Why isn't this standardized though? ay500 said 9mm clearance, is that a standard or just experience like others have had? I just seems pretty bizarre that this isn't a standard measurement, where if you mess it up, the module won't fit in a case. Although I've never head of that happening.


I think Graham Hinton mentioned in the another thread where you (I think?) just asked the question recently, that there _are_ indeed standards for this on the commercial subrack side. Unfortunately Eurorack isn't really a "real" standard... It's something Dieter Doepfer adopted for his A100 modular system from the Eurocard / Europac commercial subrack standard by throwing away a lot of the standard to make things more economic.

Hence a lot of stuff isn't really specified in any official document, there are a lot of rules of thumb and common conventions in the Euro land but basically all the "official standard" we have is the Mechanical and Electronical specifications on Doepfer's site, which define a minimal set of ground rules - some of which even Doepfer himself doesn't always follow (eg. standard signal levels).

Basically, at the time when modular was becoming cool again, the Eurorack was the framework that eventually more and more small manufacturers started designing for. And as there was no official standard beyond the quite loose one Doepfer has documented online, things were a bit all over the place regarding signal levels, keyed or non keyed power headers, tolerances of this and that measurement et cetera. Which is, basically, where we are at still.
AlX0298
Ok, ya this is very insightful, thank you flts. I do see Graham's post now, I'm thinking maybe this is a solution to be most conservative:

Jarno
?

Why the reinforcement bars?
Either support the pcb with the hardware on it (potmeters and jacks) when parallel mount, or just potmeters ig you mount the pcb perpendicular to the front panel.
indigoid
Yeah 100mm is a good height to work with. In shallow cases I've occasionally had to route power cables through the gap between rail and PCB. And yeah, cheap PCB fab.

I tend to design for 99.9mm because I've occasionally had the PCB fabs try to bump me up to the next size bracket if I have a 100mm edge. I have occasionally been naughty and let part of a potentiometer or 3.5mm jack hang over the edge of a PCB... Probably not a good habit to encourage!
AlX0298
I'm just working off the constraints of this project. The PCB is going to be probably larger and must be parallel with the panel. This idea allows me to exceed 100mm maybe even to 110 or past 110 without worries.

Alternatively I could put the pcb in front of the panel and enclose it, but I think that's not ideal.
widgetoz
AlX0298 wrote:
Can someone help me determine the maximum PCB height I should design to for a Eurorack module?

The limitation is the rail thickness. It seems to vary from one case to another. But Ive never heard of module not fitting into a case, so there must be a measurement. I know the holes are 122.5 mm apart and the holes are 3.2 mm diameter. But the PCB behind the panel must be smaller so it does not sit between the rail and the panel. So what is the maximum PCB height.

See attached picture for details.

Thank you!


See attached. 110mm is the maximum recommended. If you go larger than this you run the risk of hitting the rails in systems that use large depth rails. Rails vary in thickness from, typically 10mm to 15mm. 10mm rails would allow for a larger pcb but then you would be excluding users with larger rails.
If you really are desperate for space you should either go wider (multiples of 5mm to stay with in compliant HP panel widths) or go for double stacked boards
Jarno
AlX0298 wrote:
I'm just working off the constraints of this project. The PCB is going to be probably larger and must be parallel with the panel. This idea allows me to exceed 100mm maybe even to 110 or past 110 without worries.

Alternatively I could put the pcb in front of the panel and enclose it, but I think that's not ideal.


Think about how wide you want the front panel to be, that'll drive the dimension of the pcb (width of panel x 100mm). If your circuit does not fit on there, stack another PCB, so you can divide the circuit over two PCB's.

If you mount the pcb perpendicular, you can go to 100mm (high) x 160mm (deep) but modules that deep do not fit in every cabinet (although it is the original spec according to DIN for "Baugruppentrager" in 3HE 19").
mskala
I don't really understand AIX0298's diagram, but it looks like the idea is to have the "panel" just be a frame around the PCB, with the PCB set into a cut-out, flush or nearly so with the front of the case. That's an unusual design to say the least, and it makes me wonder why bother having a "panel " at all - why not just mount the PCB directly on the rails and have it be the panel?
AlX0298
mskala I feel I shouldn't have an exposed PCB. If I get a fancy black PCB it might look cool, but I'm not sure how strong or resilient to elements it would be.

Basically I'm trying to get it as tall as I can to retrofit some hardware from a previous project. I'm just not sure how it will all work out.
mskala
AlX0298 wrote:
mskala I feel I shouldn't have an exposed PCB.


It's true, you shouldn't. But what does your diagram mean if not that?
Rex Coil 7
I'm having difficulty understanding why some folks feel there should be a "standard" on something like this, or why the OP can't just stretch a tape on a set of rails and back off 10% to provide a bit of extra clearance?

The only "standard" is that the rails are 3U apart (outside to outside) which is 5.25". After that, there are so "standards" because there is more than one rail maker.

Standards? Are you kiddin me? There aren't even POWER or GROUNDING standards, let alone engineering dimension standards. If anything needs to be "standardized" it is the power distribution stuff, zero volt and grounding issues, and a move to far better patch cable and interconnection jacks/plugs (specifically a move to Bantam cables). And for goodness sake do away with ribbon cables as current conductors. 32 gauge wires carrying power is simply laughable.

Euro rack synths are a hodge podge of stuffs all cobbled together ... a "hobby" run wild. The only thing standardized is 12v power and that each row must fit in 3U of rack space. That's it.

Beyond that, Euro is a catch as catch can set of things that people mash together into impromptu systems.

"Standards? Standards!?! We don't need no stinkin' standards .... for we are The Federales!!"


lol
appliancide
Rex Coil 7 wrote:
I'm having difficulty understanding why some folks feel there should be a "standard" on something like this, or why the OP can't just stretch a tape on a set of rails and back off 10% to provide a bit of extra clearance?

The only "standard" is that the rails are 3U apart (outside to outside) which is 5.25". After that, there are so "standards" because there is more than one rail maker.

Standards? Are you kiddin me? There aren't even POWER or GROUNDING standards, let alone engineering dimension standards. If anything needs to be "standardized" it is the power distribution stuff, zero volt and grounding issues, and a move to far better patch cable and interconnection jacks/plugs (specifically a move to Bantam cables). And for goodness sake do away with ribbon cables as current conductors. 32 gauge wires carrying power is simply laughable.

Euro rack synths are a hodge podge of stuffs all cobbled together ... a "hobby" run wild. The only thing standardized is 12v power and that each row must fit in 3U of rack space. That's it.

Beyond that, Euro is a catch as catch can set of things that people mash together into impromptu systems.

"Standards? Standards!?! We don't need no stinkin' standards .... for we are The Federales!!"


lol


Give it a rest already and let people build/buy what they want.
flts
Edit: just edited my reply a bit so I hope not to be misunderstood.

Rex Coil 7 wrote:
I'm having difficulty understanding why some folks feel there should be a "standard" on something like this, or why the OP can't just stretch a tape on a set of rails and back off 10% to provide a bit of extra clearance?

The only "standard" is that the rails are 3U apart (outside to outside) which is 5.25". After that, there are so "standards" because there is more than one rail maker.


There are two distinct questions and I'm not sure which one you're asking:

Why couldn't there be one ("is there a realistic reason to wish there could be one")? Because Doepfer A-100 system, and hence the original loose Eurorack spec, was based on a lab instrumentation standard (DIN 41494 / IEC 297-3 / IEEE 1001.1), and matching subframes. It should be pretty clear what kinds of rails and spacing should be used because of that (edit: to clarify, it's not and everybody uses whatever they get, but we could hope someone in Germany in the '90s would have written that down as a part of mechanical specification because it was trivially available at the same source as some other constraints of the sub-rack system used...)

Why isn't there one ("why do you feel there should be one, of course there's not")? Because Dopfer didn't really care to specify that. Apparently, we could guess, because he never figured out the modular synth format he started offering in the '90s would be this widespread, and different manufacturers started using whatever profiles they could get.

To clarify: the original rail system Doepfer uses (and a lot of others, with the huge exception of Vector rails especially popular among US euro manufacturers) is meant for Eurocard PCBs, and the cards are supposed to be a certain amount smaller than the enclosure to allow for guide rails. This means the original system had 100mm high PCBs perpendicular to the panel. Obviously when Doepfer dropped the guide rails and backplane from the standard, the amount of free space would have been more than 100mm. But the point is that the measurements and rail system weren't originally just taken out of thin air - there are more mechanical definitions in the actual original standard that could (had we been lucky) have been adopted and written down at some point before Eurorack started being more than Doepfer A100.

Quote:
Standards? Are you kiddin me? There aren't even POWER or GROUNDING standards, let alone engineering dimension standards.


That is true for many other formats as well. Doepfer has some basic specifications to assure some interoperability between modules and systems (eg. the front panel measurements system, power connector and available voltages in the power connector etc.), but nothing as thorough as you require here.

Edit: to clarify, regarding power, there IS obviously a standard that the power supply should provide +-12V and optionally may provide +5V, which goes a surprisingly long way. As for engineering dimensions, you have eg. the whole 3U + horizontal pitch system which defines module front panel standard height and widths in increments of 1/5", but there is eg. no standard / maximum module depth or maximum PCB height explicitly defined.

Quote:
If anything needs to be "standardized" it is the power distribution stuff, zero volt and grounding issues, and a move to far better patch cable and interconnection jacks/plugs (specifically a move to Bantam cables). And for goodness sake do away with ribbon cables as current conductors. 32 gauge wires carrying power is simply laughable.


You aren't talking about just "having standards" here, you are talking of making a whole different set of design choices with extra costs in some cases. Eg. moving to MTA100 or MTA156 connectors and thicker cable for power would not incur that much extra cost if at all, whereas replacing garden variety 3,5mm jacks and plugs with Bantam would make amount of cable suppliers scarce and price of "volksrack" cables higher.

I'd argue you aren't now talking about standardizing (besides specifying how 0V / grounding must be handled), but using a completely different format that has technically superior specifications that you personally require. You could as well add "and the front panels should be 7U high, 3U is laughably small" to the list and soon we're talking about something entirely different thing than Eurorack with regards to form factor portability, price and so on.

Quote:
Euro rack synths are a hodge podge of stuffs all cobbled together ... a "hobby" run wild. The only thing standardized is 12v power and that each row must fit in 3U of rack space. That's it.


Well, you're exaggerating here a bit, but it is true there is no industrial standard available, just a bunch of how-to guidelines that ensure nothing blows up and by average, modules interoperate quite decently, sometimes less than so.

I'm not sure if one can find a very rigorous spec with other major modular synthesizer formats either - I haven't seen a more thorough specification regarding how to handle 0V / earth, any more accurate mechanical spec etc. with Dotcom, MOTM or Serge than with Euro, just a different set of decisions. They just sometimes kind of interoperate in a better in a way because there aren't too many 3rd party manufacturers yet (or, possibly, those few 3rd party manufacturers are more consistently professional and consider interoperability in a more careful way).
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