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Some general questions on euro-designing
MUFF WIGGLER Forum Index -> Eurorack Modules  
Author Some general questions on euro-designing
ultrashock
Right now I'm developing some project in euroformat and got an impact with taking desicions on crossroads.
Since the project is really complex, its better to predict as much as possible since it could be crucial.
So, there are my questions:
1. What holes for euro-modules are mostly preffered: round or oviform?

(the holes are usually 0.125" in diameter)
2. Are there any rules on horizontal placing of holding holes?
If we will see the euro rails - there are actually no rules since the nut goes freely inside so you can move your modules horizontal as you want. But are there any other rails just with the holes?

3. What could be the maximal PCB size that will be placed behind the faceplate so that the module'll fit the rails? I believe it's the distance between the higher and lower rails? So could you measure it?
And of course, how close the PCBs edges can come close to the horizontal and vertical faceplate borders so that the whole module finally will fit the rails and it will not be in the road with other ones?

4. When usually additional +5V pin in euro-connector could be used? Of course, additional +5V is really useful when powering some digital/TTL ICs or leds while not loading your main PSU, but it could be the PITA for those who do not have the +5V adapter (I heard Doepfer PSUs do not come with +5V power by default). So most users do not have it?
Moreover, I haven't saw many modules that use this +5V pin, even MOTM euro modules full of digital DSPs use ordinary +\-12V supply (I believe it's much more important not additional supply but to route the digital and analog ground correctly and I'm sure everything is okay in MOTM)
5. What's the easiest way to obtain +5V in your module do not using additional 5V pin? I'll try smth like L7805 (78L05 for small load)) but the heater (radiator) is really needed...


Looking forward for your tips and advices! help
Graham Hinton
ultrashock wrote:

1. What holes for euro-modules are mostly preffered: round or oviform?


The format is based on IEC 60297 aka DIN 41494. Look it up.
Manufacturers like Schroff publish an abridged version of the panel dimensions they use.

Quote:
(the holes are usually 0.125" in diameter)


You will need an M3 clearance (3.2mm). The elongated shapes are based on fitting bushings for captive bolts which vary with manufacturer. They have a side effect of helping when amateur frame makers do not realise that all this is defined by international standards and get it wrong.

Quote:

2. Are there any rules on horizontal placing of holding holes?


Yes. 7.45mm from the left edge and then on multiples of 5.08mm (0.2") across. They are NOT equally spaced.


Quote:

If we will see the euro rails - there are actually no rules since the nut goes freely inside so you can move your modules horizontal as you want. But are there any other rails just with the holes?


Tapped strips are more common than sliding nuts.

Quote:

3. What could be the maximal PCB size that will be placed behind the faceplate so that the module'll fit the rails? I believe it's the distance between the higher and lower rails? So could you measure it?


110mm. The original frame standard was intended to house 100mm high Eurocards sliding in guide rails rather than the "Eurorack" method of hanging everything on the panel.

Quote:

And of course, how close the PCBs edges can come close to the horizontal and vertical faceplate borders so that the whole module finally will fit the rails and it will not be in the road with other ones?


As long as they do not protrude past the panel. Allow a small clearance and understand tolerances.

Quote:

4. When usually additional +5V pin in euro-connector could be used? Of course, additional +5V is really useful when powering some digital/TTL ICs or leds while not loading your main PSU, but it could be the PITA for those who do not have the +5V adapter (I heard Doepfer PSUs do not come with +5V power by default). So most users do not have it?


This is a "chicken and egg" problem. +5V is not common and mostly only powers a few ICs.

Quote:
5. What's the easiest way to obtain +5V in your module do not using additional 5V pin? I'll try smth like L7805 (78L05 for small load)) but the heater (radiator) is really needed...


It really depends how much current the +5V will draw. When it starts getting a significant proportion of the total a separate power rail should be provided.

When it starts getting a significant proportion ribbon cable is not the best way of supplying it. We use separate 0.156" connectors and have a dual standard distribution card that overcomes the flaws of long pcb bus cards.
We also make +/-12V & +5V @ 1.5A FullPower PSUs (because all the others are not).

ultrashock
wow!! really appreciate for such a detailed answer. that's exactly what I wanted to know. and I really guessed that there is some industrial standard behind the 'euro-' not alike in frac or other.
ultrashock
just to update the topic I have found some "extracts" by DOEPFER from the 'euro' standards:
http://www.doepfer.de/a100_man/a100m_e.htm
and some dimentions of the frames by tiptop audio:
http://www.tiptopaudio.com/manuals/z-rails.pdf
and by Gie-Tec GmbH (who makes the rails to doepfer):
http://www.gie-tec.com/images/pic_zubehoer_19-zoll.jpg

I still have one open question: I have very tight PCB components placement, the dimentions of the PCB is exactly 150mm (width - a bit less than 30hp) x 110mm height. I have a small vertical clearance of a few components by 1-2mm out of borders of the PCB. Yet, the PCB placed directly in the center of the module.
that's why, the last stupid question that I've not found in the datasheets: can you measure this clearance? :

I guess it's exactly 110-111mm (127.8 mm of module height minus 2*10mm) or a bit higher up to 113mm (133mm of whole rack minus 2*10mm)?

upd: I've fixed all details that stand out of the PCB borders but the question is open smile
Graham Hinton
Quote:
I still have one open question: I have very tight PCB components placement, the dimentions of the PCB is exactly 150mm (width - a bit less than 30hp) x 110mm height. I have a small vertical clearance of a few components by 1-2mm out of borders of the PCB. Yet, the PCB placed directly in the center of the module.
that's why, the last stupid question that I've not found in the datasheets: can you measure this clearance? :


I guess it's exactly 110-111mm (127.8 mm of module height minus 2*10mm) or a bit higher up to 133mm (133mm of whole rack minus 2*10mm)?


The formula is (N x 44.45) - 21.35, where N is the height in U, and for 3U this comes to 112mm.
Beware that this will vary as every manufacturer has their own rail design and method of mounting pcb guides. The distance between the flanges and the mounting hole centres is less likely to deviate, but this one needs caution.

Full details are in IEC 60297-3-101 and IEC 60297-3-102.
ndkent
For what its worth, the oval holes are for mounting in Analogue Systems frames or side by side with Analogue Systems modules which use round holes with a different spacing from the vertical edge.

This could be avoided with nuts rather than pre drilled strips, but as mentioned far more people have strips and like them
John Noble
The de jure standard is from the IEC, but the de facto standard is from Doepfer.

Life in the real world differs from there.

One example of this is that case makers use two main rail systems: Schroff/Gie-Tech (and Tiptop, which differ also?) rails with a "lip" and American non-IEC Vector rails from their "TS" series.

Center-to-center hole spacing for mounting screws is specified as 122.5mm by Doepfer, so that gives you a starting point to figure out the clearance between the rails.

I've only worked with the Vector rails, and they are specified as .291 inches thick so you have a calculated 115.1mm between the rails. 110mm sounds pretty tight, especially since there might be larger tolerances in cases that have wood mounting strips instead of metal rails. I'd allow for more slop and cap the PCB at 100-105mm, but that's just me.
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