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Case Wiring, two Meanwell RT-65B
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page 1, 2  Next [all]
Author Case Wiring, two Meanwell RT-65B
ProgRocket
Hello and a happy new Year,

please help me wire my first DIY Eurorack case project with two Meanwell RT-65B PSUs. I've read hours long on this forum and others (Mutable Instruments...) and saw wiring suggestions and discussions that all didn't exactly match my case. Also i may have misunderstood some advices. I especially read Graham Hintons many patient explanations like in the thread below, but did not understand everything: https://www.muffwiggler.com/forum/viewtopic.php?t=131748&postdays=0&po storder=asc&start=100

Please check and correct me before i kill myself or my modules or burn the house down. Have i understood it correctly? Will it work proper?

[PLEASE DON'T make this a thread about the pro and cons of the Meanwell PSUs. I will exchange the Meanwells for proper PSUs. But the first try gotta be cheap.]

I've learned

  • to have ground star wiring
  • the ground star to be as close to mains inlet as possible
  • to use as thick wires as possible, especially for the ground
  • to wire as short as possible
  • to NOT junctions wires at terminals (hence the many WAGO connectors)
  • to NOT serialy connect the busboards - rather to connect each busboard on its own
  • to NOT connect meanwells COM (0-volt) to the busboards but rather to connect the busboards GND to mains-earth/chassis GND as well.
  • to use a 10 Ohm resistor as minimal load on the 5V line so the PSU won't whine which will constantly generate 2x 2.5 W heat dissipated through the aluminum case and some ventilation slits

djs
ProgRocket wrote:

[*] to NOT connect meanwells COM (0-volt) to the busboards but rather to connect the busboards GND to mains-earth/chassis GND as well.


0v (COM) needs to be connected to the busboards, along with the GND (mains-earth). Otherwise your PSU will have a floating 0v reference that may or may not agree with the earth-GND, and cause all sorts of problems.

Also- what's the function of the orange connector in the middle with all of the GND connections going into it? Creating some sort of connection point for all of the grounds?
djs
Forgot to mention- those meanwell supplies only output 0.5v on the -12v rail, so you may hit some limit before you realize.
ProgRocket
Thanks for your reply, djs! Here's an upgraded scribble with COM connected to mains earth as well. Would that be correct?

- Do you confirm that i should NOT be using the busboards second terminals and NOT connect the busboards in series? (Wiring them in series would make things so much simpler ...)
- Are the resistors used correctly?

(Yes, that thing in the center are two, now three, 5-pole WAGO-Connectors, rated for 32A and clamp woven- or solid copper wire of 12-24 AWG)

I know about the 0.5A limitation on the -12V. I read somewhere that it 'borrows' from the 5V line up to 1A (not knowing what that means, just paraphrasing). Nevertheless i should be fine with 2x500mA. I will be at ~600mA on -12V when i have my third row of 104HP full. I will exchange the PSUs later on when i start the 4th row, perhaps...)

djs
ProgRocket wrote:
Thanks for your reply, djs! Here's an upgraded scribble with COM connected to mains earth as well. Would that be correct?

- Do you confirm that i should NOT be using the busboards second terminals and NOT connect the busboards in series? (Wiring them in series would make things so much simpler ...)
- Are the resistors used correctly?

(Yes, that thing in the center are two, now three, 5-pole WAGO-Connectors, rated for 32A and clamp woven- or solid copper wire of 12-24 AWG)


When you connect the busboards in series, it "can" work, but most likely you'll have ground issues between them. If you do it the way you have it in the pictures, it'll be more likely to work properly, and you'll save yourself some headaches in the long run.

As far as the COM->GND (earth) connection, it's better done at the busboards, not at the connectors in the middle. This is what you could use the busboards' second terminals for?

For the center connectors- I had a hard time finding the exact type of connector, but the best I could tell was that these are screw down connections... are the different sections connected to each other? I'm a little confused as one of your connectors shows all 0v/ground wires going thru it, but another connector shows all voltage lines going thru it? How does this work?
TheSlowGrowth
Your dummy load should be between 5v and GND not in series with the 5V. I use meanwells as well, not this model though, and I never needed dummy loads. See if you really need them before you add this heat source to your rack.

You should wire the GND on the primary side of the PSUs directly to the mains inlet. It is from the AC input filter and it's better keep that current away from the GND star point because that is your signal reference which you don't want to get disturbed by the crap that was filtered away from the mains voltage.
ProgRocket
Thanks for chiming in, Slowgrowth. Here is a new scribble taking heed of what you both said.
  • COM->GND (earth) connection better done at the busboards, not at the connectors in the middle ... use the second terminal for that
  • Your dummy load should be between 5v and GND not in series with the 5V.
  • wire the GND on the primary side of the PSUs directly to the mains inlet

@djs: i hope this scribble also clarifies the connectors. Here is product video about them on youtube: https://www.youtube.com/watch?v=n8gLG6c-iKc

Is this the best way to do it?
TheSlowGrowth
djs wrote:
As far as the COM->GND (earth) connection, it's better done at the busboards, not at the connectors in the middle. This is what you could use the busboards' second terminals for?


I don't get this. Why? The GND should go to the star point. With this suggestion you create a loop in the GND wiring.
djs
TheSlowGrowth wrote:
I don't get this. Why? The GND should go to the star point. With this suggestion you create a loop in the GND wiring.


It was a comment by Graham Hinton in one of the previous discussions- basically having the 0v+GND linkage closer to the distro board means that the 0v will be more stable? I'll see if I can find more details.
MARK27
I'm curious about this as well. I'm building a case with two L-1 PSUs and I'm wondering if I need to somehow connect the 0v.

Old dude from L-1 said that the grounds were connected at the "net power inlet." Maybe that only applies to the L-1 PSUs, but I was curious because I see the notion repeated so often when discussing multi-PSU cases.
ProgRocket
seriously, i just don't get it Now i am stuck, I need some consensus! Maybe it's all overthinking and not that bad to go with a _much_ simpler wiring, as in these case from MDLR - they sell them for 650 bucks after all, got to be working, right?(frankly i frown on all the unisolated mains voltages confused ).

Too bad i can't quite gleam ALL of the wiring from the pictures.
TheSlowGrowth
To my understanding, the central star point is your global reference. Everything except the mains filtering should go directly there and the start point should be connected to the mains earth (though in theory it doesn't have to). If you keep the GND wires nice and think, noise should be minimal.

If you have just a single distro board it could be (minimally) beneficial to have the link to mains earth closer to the busboard. But with multiple busboards that would only create loops and be more harm than good.

Loops can be problematic because they can pick up magnetic fields and the resulting ring current will cause fluctuations in the reference voltage. No loops - no problem.
Everything else is about preventing current spikes from creating voltage fluctuations. The star arrangement will keep the voltage fluctuations in one arm of the star away from the others and thikc GND wires reduce the impadance which makes the voltage fluctuations smaller.

Translating this into a wiring scheme means: star arrangement with thick GND wires. Star point connected to earth because that is the point closest to the busboards and still common to all busboards. Mains filtering directly to the mains earth terminal so that the current from that doesn't flow through your earth-star-point link and hence doesn't disturb the reference point more than necessary
Bamboombaps
long shot- does anyone have spare covers for these PSUs? i have seen them on threads here and there but no idea where they come from.
ProgRocket
@Bamboombaps. I created a 3D model... on Thingyverse
https://www.thingiverse.com/thing:3309423 or tinkercad https://www.tinkercad.com/things/g3FBf97guWa
The terminal cover is not tested yet.

@TheSLowGrowth:
Please bear with me one more time and lets make this foolproof.

You say: "the start point should be connected to the mains earth" and "Star point connected to earth because that is the point closest to the busboards and still common to all busboards." .
-> I would connect all busboards GND to a central star and connect this star to mains inlet earth.

You say: "Mains filtering directly to the mains earth terminal, so that the current from that doesn't flow through your earth-star-point link"
-> I don't understand. What do you mean by mains filtering? But guessing your meaning, I would connect both meanwells earth terminals to the mains inlet earth (effectively also connecting it to the groundstar, as per your description above. Isn't that contradicting now?)

You would leave the Meanwells COM-terminals empty/unconnect, is that correct? But then the outputs are floating and are not referenced to each other.
Bamboombaps
thumbs up
TheSlowGrowth
ProgRocket wrote:

-> I would connect all busboards GND to a central star and connect this star to mains inlet earth.

Correct.

ProgRocket wrote:
What do you mean by mains filtering?

The Meanwell PSUs have a filter at the mains input. That filter is mainly used to prevent high frequency noise from the PSU from flowing back into the power lines. This filter needs a connection to earth, and some of the RF noise is flowing to earth over this connection. If you connect this terminal to the star point, this noise current will flow from the filter terminal to the star point and then to the mains inlet earth terminal and finally through the power cord. There's a small resistance (actually: impedance) in the wires so there will be a small voltage difference between mains earth and the star point and this voltage difference will also appear in your audio signal as that is referenced to the star point (actually to the modules local GND connection on the busboards). By connecting the filter terminal directly to the mains inlet, you decrease the length of wire through which the noisy current has to flow and so your reference point will be less disturbed.


ProgRocket wrote:
guessing your meaning, I would connect both meanwells earth terminals to the mains inlet earth. [...]
You would leave the Meanwells COM-terminals empty/unconnect, is that correct? But then the outputs are floating and are not referenced to each other.

Yes to the first sentence.
And No to the second one. The primary and secondary sides of the Meanwell PSU are isolated from each other. The COM terminal is the return path for the current of the other secondary terminals so it must be connected to the star point.

Basically, all you do is: imagine along which paths the currents flow. Then you have to provide a short path for all the currents so that the voltage drops created by the currents become minimal. The ultimate goal is to have your signal reference potential (which is ideally equal to mains earth) as independent from the power supply currents as possible. One way is thick wire and small inductances (short wire runs, no wrapped/coiled wired runs), as less impedance means less voltage drop. The other way is to provide separate paths for the currents so that some of the voltage drop stays away from your reference potential. The star helps here because voltage drops created in one arm of the star do not affect the other arms. Ideally, all ground connection points in the circuit would have their own, super low impedance connection to earth (a star with many, many arms), but that is of course not possible. Using more arms in the star wiring is a practical solution.

All of this applies to GND and also to the supply rails. But in a well designed module, there will be local regulation and a high PSSR (power supply noise rejection ratio). Hence the supply rails are not nearly as critical as the GND wiring.
ProgRocket
Thank you for the helpful explanations, theslowgrowth.
I think this then would be it:
Does everybody agree?

Mungo
ProgRocket wrote:
Thank you for the helpful explanations, theslowgrowth.
I think this then would be it:
Does everybody agree?

The basics of the 0V and power supplies are all well thought out now, but still some safety issues.

With those power supplies the mains earth is for safety, it needs to be connected directly from the inlet to the chassis and not via a terminal block. Tie all the chassis together separate to the 0V distribution (not through the bus boards). If it will be possible to touch the cases of the meanwell power supplies they should be wired directly from their FG terminal back to the chassis point where the mains earth first connects. Use an M4 or larger bolt and shake proof washers for the chassis earthing connections.



To tidy it up some more don't be too worried about using a couple of ring terminals on top of each other, you can eliminate the terminal blocks to distribute the power rails to the bus boards and just wire back directly.
ProgRocket
Mungo that's fantastic! Thanks a lot! I will do it exactly like that.

I have one problem though, and one more question.

- At the mains inlets i can't crimp two AWG 13 (2.5mm square, 1.7mm diam) wires into the 4.5mm tab-connector/terminal. The crimp-end will permit just one 2.5 mm2 wire inserted. Can i really not use the the WAGO connector? Like so?


- Stacking ring terminals? I read that any stacking of terminals on a terminal block is a No-Go - that's why i went with all those very safe WAGO clamping connector blocks. What's more reliable and gives the cleaner voltages? Or is it no difference at all?

Again thanks for checking security!
Mungo
ProgRocket wrote:
Mungo that's fantastic! Thanks a lot! I will do it exactly like that.

I have one problem though, and one more question.

- At the mains inlets i can't crimp two AWG 13 (2.5mm square, 1.7mm diam) wires into the 4.5mm tab-connector/terminal. The crimp-end will permit just one 2.5 mm2 wire inserted. Can i really not use the the WAGO connector? Like so?
The mains earth from the plug or cable should go directly to the chassis, not via several connections. When needing to distribute it further you can use a terminal block that splits it out after first going to the chassis:
http://www.interpower.com/ic/designers/in-depth-product-line-informati on/More-Information-on-Terminal-Blocks.html
If you can't get the right sized crimp and tool to put two 2.5mm^2 cables into the single terminal, then the next best option is putting several rings on the chassis grounding screw.

ProgRocket wrote:
- Stacking ring terminals? I read that any stacking of terminals on a terminal block is a No-Go - that's why i went with all those very safe WAGO clamping connector blocks. What's more reliable and gives the cleaner voltages? Or is it no difference at all?
Stacking of ring terminals is ok, not so for fork terminals as they can push out. You need to keep a constant pressure on the joint(s) to maintain the low resistance so its very important to use shake proof washers. The spring/push in terminals you are suggesting just add more joints and complexity, doubling up ring terminals on the outputs of the power supplies will be much better.

For the assembly you will need some way to keep fingers away from all the mains wiring and connections, and hold all the cables down so that if any one of them came loose they couldn't contact between the mains and low voltage parts.
ProgRocket
I feel awkward to pester you hmmm..... but after what you said now and the illustration you gave (in short: "mains earth from the plug directly to the chassis, not via several connections... to further distribute use a terminal block AFTER first going to the chassis")... further above you also said: .. the meanwell power supplies should be wired directly from their FG terminal back to the chassis point where the mains earth first connects. Why then it's not like this?



(I DID however understand you, that i could stack 4 ringterminals on the chassis ground as my next best option.)

But i don't want to question your scribble, it's just i still don't understand. cry Anyway, here is a cleaned up version, hopefully the last, with shake proof washers etc... I found the yellow 4.8mm crimpterminals that can take 6mm² wires (or 2x 2.5mm²). For the L an N wires however i feel safer with the WAGO-clamps.



I will insulate with shrinktube, use hotglue (not mutant), use cable binders etc. And i will let an electrician check it, before i plug it in.

Here is the actual 3D-Print of the terminal cover 3D-model. It fits perfectly to the Meanwell RT-65B, just needs a bit of filing. Go ahead and print it!

Mungo
ProgRocket wrote:
I feel awkward to pester you hmmm..... but after what you said now and the illustration you gave (in short: "mains earth from the plug directly to the chassis, not via several connections... to further distribute use a terminal block AFTER first going to the chassis")... why then it's not like this?



(I DID however understand you, that i could stack 4 ringterminals on the chassis ground as my next best option.)
They are both good choices, and now come to opinions and conflicting requirements or standards. Personally I would use the second type and daisychain the FG earths to each Meanwell supply, but the terminal block ok too. What is important is that the noise from the FG is not flowing down the same connection as the 0V, either the earth pin of the power inlet is the single "star" point or the chassis ground bolt.

ProgRocket wrote:
But i don't want to question you, it's just i still don't understand. cry Anyway, here is the scribble cleaned up, with shake proof washers. I found the yellow 4.8mm crimpterminals that can take 6mm² wires (or 2x 2.5mm²). For the L an N wires however i feel safer with the WAGO-clamps.



I will insulate with shrinktube, use hotglue (not mutant), use cable binders etc. And i will let an electrician check it, before i plug it in.

Here is the actual 3D-Print of the terminal cover 3D-model. It fits perfectly to the Meanwell RT-65B, just needs a bit of filing. Go ahead and print it!

Looks like you have all those important little details thought out ahead of time and ready. Thanks for sharing all this information so others can benefit from it.
ProgRocket
Thank you all so much! SlayerBadger!

I'll post updates of how's it going along. I am sure other newbie case builders will be interested in some more steps, too. Cheers!
Joker Domino
This is great learning, thanks all.

I have a similar setup to @ProgRocket that I'm hoping to DIY... Starting off with 2x PSUs but it will end up with 4x PSUs I'm sure.

Case is wooden so no need to ground the chassis so my question relates to the earth distribution terminals, is this design overkill?

Can I simplify it and run all the PSU COM and busboard GNDs to Earth distribution A and therefor discard B?

Joker Domino
Looking at the Doepfer and others they seem to just use a simple Earth > PSU and then run the PSU COMs to the busboard's GND...

This setup is obviously ok - Sufficient for my wooden case or best to go full-on earth?


Thanks,
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