To hook up the ATX and AT so they at least start at the same time, you would need to use a relay. Due to the fact that the other PSU runs without being hooked to the mobo, I'd have to say it is an AT. Here is an article that will give you the general principles for doing a realy hookup(though related to a different pupose); http://www.overclockers.com/tips242/
I just finished installing a second power supply in a different box that I am building.
Both of these are atx so I hard wired them together.
I mounted the second one in two 5 1/2 bays on the front of the box with the fan and switch on the outside.
I removed the socket for the power cord and wired a piece of of power cord from the forward psu to the socket terminals on the back psu this way I only have one cord to deal with.
So far it tests out ok, the front psu is for fans and drives and the rear is for the mobo only.
Folks working this thread here are looking for a nice way to have both psus power on by pushing the original case switch, without having paper clips around--and off.
If you take a peek at my picture of my test setup, you may notice something...
I personaly used this method for about six`ish months before i decided to buy
myself a new antec truepower 430watt and it worked ok for me "no problems"
But since i have a spare "generic" 300watt power supply lying around doing
nothing i figured i would have a browse around and try to find one of these
addapters found Here: but it appears that they no longer make or stock them.
So im looking for an alternative, anyone got any recent news or any
new linkage to some good info regarding dual power supplys? as some of them
links are now dead and surely someone somewhere has a decent recent guide!
Well after doing a hell of alot of research about this i actualy thought it looked a little too complicated at first and i wasnt
going to bother but seeing as there is a very simple way to get both power supplys to turn on at the same time using
the same switch im real pleased and im off to do that, .
Had a little time and some spare parts from another failed mod, so here is another method.
I happened to have one of these:
This is a radioshack micro 5V DC SPDT relay switch, link here. Costs about US$5. I'm not an electronics expert but I'll try to explain the terminology:
This particular relay switch means that when 5V are applied to the coil end of the device, this will cause it to throw a switch. SPDT means "single pole double throw", which describes the switch it will throw--a single switch, but will toggle between 2 circuits (double pole). You can also use a SPST NO switch, which means "single pole single throw normal open", which means that instead of toggling circuits, when activated it will close the circuit. This will make more sense when we get to the circuit diagram.
I chose 5V because I've wired the relay switch to a standard 4 pin molex connector (black to red wires). You can also probably use a 12V (black to yellow). I happen to have my own molex wire, pins, housing, and crimper. Otherwise you can just sacrifice a molex adaptor.
Here is some more info about the relay switch:
Here is the wiring diagram:
So the plan is to connect pins 1 and 2 across a 5V molex line of the master power supply. When the master power supply is turned on, the 5V will apply across the pins and activate the relay switch.
While the switch is inactivated, pin 3 is connected to pin 5, so we will leave pin 3 alone. Note in a SPST NO switch, there will be no pin 3.
So then pin 4 and pin 5 are to be connected to the ps_on (green) and a ground of the slave ATX connector. Thus when 5V are applied to the switch, the switch will close pin4 to pin5, jumping the ps_on to a ground, and thus activating the slave ATX.
Here is the wiring in real life:
And here it is working:
Pros and Cons of this method over the dual ATX connector method:
Pros
1. The dual ATX connector requires an additional adaptor the sits between the main ATX power supply and the motherboard, which adds resistance. This molex-to-relay does not.
2. Molex connectors are much easier to wrangle and handle than ATX connectors.
Cons
1. The relay switch has a theoretical lifespan.
2. The molex-to-relay switch adds a little resistance to the 5V line.
I've been thinking of doing dual PS mod as well, using a relay to control the second PSU that is a spare 300 watts AT. Since it's AT it has physical power on/off switch which a relay can work perfectly. I'd like to move all the fans and lights to the second power supply and eventually add peltier if the summer heat proves a little too much for my PC with water cooling. Since it'd only be light and accessories, I shouldn;t need to worry about proper grounding at all and have the second one completely isolated. Right? I can also use the same relay to handle the 120v water pump as well so there'd be less messy wires on the outside.
My main PS is 600 watt (350 watts 3.3v + 5v) but with a few fans, 5 hard drives, DVD burner, DVD-ROM, 1.5GB RAM (3*512MB DDR400), OC'ed P4, 256MB FX5600 AGP, and 4 PCI cards I'll bet there is not a whole lot of power left.
In regards to grounding your PSU as long as it is grounded in the wall outlet you should be OK.
As far as using one relay to power both the PSU and the Pump that is dependent upon the Amp rating of the relay. If it is a SPDT Relay I would look at the amp ratings of the PSU and pump carefully. DPDT I would just put each of the unit on their own contact and you should be fine provided the relay can handle the amperages.
I am looking to install 2 PSUs in my PC, one for the mb, hd, etc and the other for fans, cathods, optical drives, etc.
My problem is that the second PSU can't power up, cos it isn't plugged into the MB like the primary one How can i get it to power up? i don't really want to cut wiers, etc.
Hi that's the whole point of this thread. I've continued to occasionally look around the net for prefabbed products, but have yet to find one. I even talked to hank at performance-pcs, who specializes in custom cable adaptors, and as of yet no one offers them.
I continue to offer to make them for folks, feel free to pm me. I have 2 methods (ATX extension vs 5V molex relay switch--see my posts above for the difference). But I'll need to know what type of psus (20pin ATX or 24 pin).
I plan for my 450 watt To power my mobo, HD, and video card, Second will hold Drive, lights and fans. I have a mid ATX case... There is no where to put the second psu. Anyone solve this problem?
I'm building my own computer and I started modding two of my older PSU's into one for more power. But I need some more advice on whether it is possible to 'join' the +12V and the ground of one PSU with the +12V and the ground of the other PSU, to get more amperes. I've been told that in theory it is possible to do this simply by soldering everything in parallel but then again I think in practice the higher current of the 300W ATX PSU might try to charge the 200W AT PSU and cause a hell lotta trouble..
I abandoned the 'diode isolating' idea, and just putting everything in parallel probably won't work either. The only possibility left is using mosfets 'at the end' of both the 12V rails and then joining both ends in parallel. How this works can be found on http://www.procooling.com/articles/html/sharing_the_load_between_psu_s.php; here are the pro's:
"Minimal voltage drop (less than 0.2 V in most cases, mosfet resistance is 0.0078 ohms), no possibility of the supplies attempting to charge each other. It also shares the power so that both supplies share the load equally."
Does this mean that both PSU's will try to supply the same amount of amperes, either giving a lower total amperage or blowing up the weaker PSU? If this is the case, can I somehow prevent this from happening, maybe by using two different mosfets and/or fet drivers? I know I could save myself a lot of time and trouble by just buying a new (or possibly two equal) PSU('s), but I'm willing to learn how electronics works and I just like this project. I might post some pics here, too.
So if I just connect the green from the master to the green on the slave and grounds on both together it will power on the slave? I just want to run my pump and fans with the slave, I will be running a 300w sparkle as slave to my 530w fortron.
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anyone got any recent news or any
