Mendel90 PSU Help - USA

Hello fellow Printers,

I'm going to qualify this by saying that this is my first build, first foray into electronics, and first time with a soldering iron . So far, I've managed to use what I've picked up over the years, what I remember from shop class, and what I've searched up on the internet to get pretty darn far into this build. However, I'm at an impasse with the power supply. Being that it was my first build, I ordered Nophead's Mendel90 kit (superb quality, by the way!), but being from the US, it did not ship with a power supply. I knew going in that I would have to make some adjustments, and that is where you all come in. Please help me figure out how to convert this power supply for use with this printer.

Okay, so here we go:

There are (on the 24-pin):

5 orange wires
5 red wires
8 black
2 yellow
1 blue
1 green
1 gray
1 purple

8 additional black wires on the CPU power pin

And pictures (for clarity)

Pictures

Thank you in advance!!!

I detailed some of my PSU modifications in this blog sometime ago: Blog Post

Here is a detailed write up :
[reprap.org]

Wozzy and Ralph, thank you for your quick responses. Lots of great information (additionally lots of stuff that went right over my head )

My apologies... but....

So knowing nothing about how electricity works... I'm still a little lost. While I'm less lost than before, I feel more likely to start a fire with the knowledge that I've gained (the truth is, this was a project for me to do with my younger brother and he.... "oversold" his qualifications).

Can someone walk me through it a little more, ya'know dumb it down a bit?

Just follow the instructions in the manual. The only difference between different ATX supplies is the number of wires of each colour. The colour codes are standard apart from the 3.3V sense wire, which is brown on the PSUs I use, but is sometimes orange. You can identify it because it will be smaller diameter than the other orange wires and will be connected to one of them in a pin of the large connector.

So you treat all the wires the same as the wires of the same colour in the instructions. If the wires are a bigger gauge you might not be able to fit as many yellow and black ones in the Melzi terminals. If so just use as many as will fit and insulate the spare ones.

There is no need to open the PSU and it is dangerous if you don't understand electronics.

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[www.hydraraptor.blogspot.com]

So in that case I would just use two yellow wires instead of the 6 that the manual calls for?

yes.

Do you have an current output specification from the power supply manufacturer for the 12V rail.
That's a little worrisome that it only has 2 x 12V wires.

It looks like the circuit board has labels where the wires attach.
Is it labeled +12V for the yellow wires?

Can you determine the wire gauge used for the two yellow wires?

I'd recommend making sure they don't get too hot when first using the printer, especially when both the Hot-end and the Heated bed are used

Nophead probably knows the maximum current draw required by the Mendel90.

Wozzy,

!

I think I may have a solution. If you take a look at this picture, you'll see that there is a bundle of black wires wrapped in YELLOW sleeving on the right side. This is significant because those four wires go the the CPU pin. They come out of the same place on the board as the other 12 v yellow wires. Additionally, there are four black wires that also go to that 8-pin cpu fitting that track to one of those bundles labeled GRD (ground?).

Can I bundle those 4 wires with the two yellow, then I'd have 6!

for reference, this is the power supply: [www.corsair.com]

The picture doesn't show where the yellows come out. Connecting yellow wires to black ones sounds disastrous.

The machine takes a maximum of 16A.

All the wires of the same colour are connected together in the PSU. Just remove all the connectors and treat all the yellow wires the same and do the same with the other colours. There must be more than two yellow when you include the drive connectors, graphics card, etc. Use as many as will fit in the connector. That means you will have the same cross section of copper, regardless of wire gauge.

It does look like the 8 pin connector has all black wires, which is non standard. Either ignore all those or use a multimeter to find which are also connected to yellow.

Edited 1 time(s). Last edit at 03/15/2014 08:18PM by nophead.

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[www.hydraraptor.blogspot.com]

Update: Had a snow day today, so I was able to take another look at the PSU;

This picture shows what I'm taking about a little better. IF a ATX CPU connector is made up of four power and four ground wires, than corsair must have wrapped those four on the right in the yellow sleeve to indicate that.

Another Angle


I'll test with a multimeter, obviously, but does that make sense?

Yes the Corsair page shows the 8 pin connector having four yellow and four black wires. They obviously cut corners and used all black wires but had to put yellow sleeving on so their own staff could solder it to the correct PCB hole.

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[www.hydraraptor.blogspot.com]

Quote
nophead
Yes the Corsair page shows the 8 pin connector having four yellow and four black wires. They obviously cut corners and used all black wires but had to put yellow sleeving on so their own staff could solder it to the correct PCB hole.

It likely was more an aesthentic decision then to cut corners. It's a modular power supply and aside from the main motherboard bundle which looks like it normally is wrapped in a black wire sleeve, all the cables are black. The 8 pin connector is two 4-wire flat molded cable so having a black cable and yellow cable was technically possible, it went against the desire to have all-black cabling.

It also likely was signifiantly cheaper (from a production standpoint) to stock twice as much black cable and just have a yellow ferrule to put on one end then to have two colors of cable assemblies plus having to wrap the cables in a black sleeve. 99.9% of their customers don't care what colors the individual wires are, and I'd guarantee more of them are more concerned that they were all black then if they were the official colors of the ATX spec.