daisychaining 2 (or more) ATX computer PSU

[posix]

Ok, can we have some sort of a sticky thread about the procedure of daisychaining or connecting in series 2 or more ATX power supplies to get more volts for our puny steppers.

Also I have a question.

Currently I have one ATX psu, 5v powering the drivers and 12v powering the motors. What happens to my 5v if I daisychain the 12v of 2 PSUs? Do I still have the 5v for my drivers and 24v for the motors or is the 5v doubled as well?

A nice drawing would help here as well as I've allready had my share of electric shocks to last me a lifetime and my heart can't stand the increased blood pressure induced by surprise jolts and sparks. AND I get a massive headache afterwards!

So, is my "diagram" correct? Any other "hidden extras"?

[posix]

Actually, there's only 5v going into the driver board, no separate ground.

[NC Cams]

Take your 5V from the BLUE transformer as it is your "ground/ground".

The 5v from the green P/S is PROBABLY gonna be 5v above the output of the blue

[posix]

erm...yes yes...of course! no you lost me mate. can you repeat that just slowly this time?

[NC Cams]

1. Disconnect 5v from GREEN P/S



2. Reconnect 5v to BLUE P/S



3. +5 and ground go to drive from BLUE P/S, NOT green.



4. Delete ground lead from GREEN P/S to drive card.



As simple and slow as I can type....

[posix]

aaahhh ooooohkaaaaayyyy

but now which one has it's ground disconnected from the chassis, green or blue?

[NC Cams]

The typing isn't presented quite as slowly but it the explanation is put forth in great detail AND with pictures here:

http://www.procooling.com/index.php?...s&disp=52&pg=1

[posix]

I have read all that but the "procooling" article deals with a single device i.e. fan connected to two power supplies in series. what I was wondering about is what happens when you add a driver board to the equation i.e. motor at 24v and driver board at 5v. does that work? and whether I should disconnect the ground from the chassis of the green or blue psu, bearing in mind the driver is connected to the 5v off blue psu.

Is the updated "diagram" the correct one?

I hope I made myself a bit clearer this time.

If not, I can type reeaal slooow?

[posix]

Ok, I bit the bullet and did what is shown in the picture. And everything works fine!!!

I even have a 3rd device, a 12v computer fan blowing cool air across the drivers.

I have gone from 6revs/second and stalling to 21revs/second and running fine! But cooling requirements grow exponentially! (Linistepper users take note and be warned!)

[NC Cams]

Congratulations. You did what I intended/suggested but didn't have time to reply to your prior reeeaaal sloooow typed letter.

What happens:

The blue P/S now has has black wire at "ground" potential. Thus, the +12 and +5 were all 5 or 12 volts above "ground".

In your earlier design, the proposed 5v would be at 5v ABOVE the GREEN P/S black wire and 5v ABOVE whatever potential the GREEN supply reached with respect to the BLUE's black "ground" wire.

Check it out some time hooked up the original/other way, albeit NOT connected to the drive. Put your negative lead of vom to the BLUE ground then the positive lead of vom to the +5 and +12 of the GREEN P/S. For grins, then check voltage of -12 of GREEN.

At that point you should see what went on... no matter how fast you type. 8-)

[posix]

Great. Can we make this sticky now, please as this subject keeps popping up often.

[NC Cams]

Whomever knows how to move/copy this to FAQ section, it would be appreciated.

I don't know how and claim to be too old/senile to learn. 8-)

EDIT: if you wanted 36 vdc, you'd simply disconnect "plus" lead from the GREEN p/s, plug in another ala the "GREEN P/S" method (don't forget to remove internal chassis ground ala GREEN "snip") and reconnect.

Ditto that for 48v.

NOTE: there are some important precautions to take when modifying AT/ATX P/S's. Check the prior link for this information.

If it is not too tough to do, a couple illustrations showing these 36 & 48 v options would be a nice contribution.... The illustrations really simplify the explanation.