official GDIY51PSU Help & Support Thread

[mikefatom]

Hello JDB,

Would you be able to guide us through the math involved here? How did you get the ~1A per rail current limit from a 1.5A transformer? How did you get the "eight normal 500-series modules" figure? How do you figure that 2.2A per rail would give enough juice for 12 modules?
How do you go about figuring out the safety margin?

Really interested as I am designing something similar for a set of pres soon...

Cheers

Mike

A few nits:

With that transformer you're limited to ~1A on the main rails. Why use an LM350 in that case, instead of the more ubiquitous LM317? It looks like you're limited by dissipation not max current, and the thermal resistance of both parts is almost the same, limited by their TO-220 package.

the PCB is designed to power up one Rack, with 12 modules installed needing the max power of all 5 rails.

With a 2x16V/1.5A transformer this PSU can only power eight normal 500-series modules (@130mA max per rail). You'd need at least a 2x16V/2.2A transformer to feed a dozen.

Am I missing something here?

JDB.

 

[matta]

Guys,

Not to break the flow, but can I just thank you all again for all your efforts. Volker, Cemal, Jeff, you are legends, having done a few Group Buys before I know what is involved to put this all together, and NOTHING I've done has come close to this magnitude, so again, Kudos, your many hours, days, weeks and months will prob never see a full financial reward, but we thank you for your dedication to this project.

Ok, back to our scheduled programming....

Matt

 

[[silent:arts]]

Matt,

you have started this in some way
thanks for the kind words.

it is not that easy like it might look, 3 personalities, 3 countries, 4 mentalities
but also 3 friends now, I'm sure. even we never have met us in person. (last point is sad)

while we have still not sorted out the real costs our debates are more about the next batch.
stupid we are.

however, why is this in the PSU support thread  ??? ??? ;D

 

[matta]

however, why is this in the PSU support thread  ??? ??? ;D

Hey I thought this is a place for SUPPORT, I'm SUPPORTING you  in the SUPPORT thread :

Matt

 

[jsteiger]

while we have still not sorted out the real costs our debates are more about the next batch.
stupid we are.

Haha LOL...sad but true!! I wish I was counting all the emails! 

BTW, one day we will meet in person. I will buy the first round of beers!  ;D

 

[jdbakker]

Would you be able to guide us through the math involved here?

In a nutshell, cutting a few corners:

The voltage specified for a transformer is the RMS value of the AC voltage.
After rectification the voltage on the buffer capacitor is the peak voltage of the AC voltage, which for a sine wave is 1.4x the RMS value (or sqrt(2)).
Now, the max power drawn from the transformer is (of course) unchanged by rectification. But the voltage is 1.4x higher, so the max current must be 1/1.4x or 0.7x the rated AC RMS current of the transformer. So, to have 12x0.13=1.56A at the buffer cap, you need a minimum transformer rating of 1.56x1.4=2.2A.

(the real story is more complicated, as the charging current through the rectifier diodes is rather more spiky than a normal sine wave, so the RMS value is relatively higher, so the transformer will see more dissipation. A safer factor is to have the DC out current be between 0.6 and 0.65x the rated AC current, or 2.4...2.6A for the earlier example)

JDB.

 

[Ptownkid]

I kept meaning to ask this, why has a 9 way connector been suggested for this? It's my understanding that all you need is 7 (or 6 if you wanted to combine chassis and ground).

 

[mikefatom]

Thank you for the explanation JDB. It makes complete sense.

Cheers

Mike

 

[RedNoise]

Could someone tell what kind of wire he uses to join PSU to the 511 please?Maybe a good link to help me to check the "datas" needed...?
thx

Ok , EDIT , found Holger's post @ the daughter board :
602761-52  @ Conrad
Sorry!
http://www.conrad.de/ce/de/product/602761/?insert=52&productname=STEUERLEITUNG-7G1-GR-OeLFLEX-100

 

[Ptownkid]

What is the current rating on that cable? I can't seem to find it, even on Lapp's english site.

 

[[silent:arts]]

since a few people asked if they can place the GroupDIY 51X Alliance logo on their PSU chassis:
yes, you can.

Frank from nrgrecording was kind enough to convert it to fdp.
hint: he makes the best engraved frontpanels

ok, if you are based in the EU you will contact Frank, won't you.
and if you like to place the logo on your own:
51x-Logo.fpd

thanks Frank!

 

[jsteiger]

I don't think I mentioned it yet but I have a custom toroidal transformer sample in the works for the 51x PSU project. The company I am dealing with will do 1 prototype free of charge before I commit to a large production run. They have the spec sheet correct but on the advice of some wise friends, "get a sample first". I should have that in about a week and a half from now.

I think Volker and Cemal have a large batch coming from Volker's trafo guy in Germany.

Cheers all, Jeff

 

[Ptownkid]

I thought you were making a psu chassis Volker?

 

[[silent:arts]]

I thought you were making a psu chassis Volker?

Cemal has one in the work.

 

[jsteiger]

Cemal has one in the work.

A very sharp looking one it is!

 

[[silent:arts]]

just came home and had to bring some 110 kg to the 2nd floor 
50 more PSU transformers arrived ...

Cemal, I think you should receive your 50 pieces soon  ;D ;D ;D
we are Mueller VIP customers now 

now I hope the PSU PCBs reorder will arrive soon too.

 

[Ptownkid]

how much are you selling those for Volker...and how much is shipping to canada? (L1T2A2). I really want to get my rack up and running.

 

[[silent:arts]]

those are EUR 41,70 (for all EU customers: excl. 19% VAT)

since it is more than 2 kg shipping to canada is expensive (I can only use DHL).
shipping up to 5 kg would be EUR 35 (might be ok if you take 2).
uninsured (since not offered), 10 days (not guarantied), hard to trackable.
it sucks.

might be better to wait a little for Jeffs transformers.

 

[Ptownkid]

cool, thanks!

 

[jsteiger]

Hi guys,

In creating the product page for these PCB's I have a question. Keep in mind, I am buffoon when it comes PSU electronics. If someone has the proper toroidal trafo, what would it take to build out the board to have all 4 main voltage rails operating at 16V? Would it be as simple as changing out R11, R21, R13 and R23 to match the values for the standard 16V parts of the circuit?

Just thinking about those people who for some reason would only desire standard 500 series modules. This could be a very solution to power 2 full racks of 11 modules.

Best, Jeff