jsimmons
06-22-2005, 05:42 AM
I recently built out a new case because I wanted to split my cooling loop (one loop for the CPU, and one for the GPU). Since I am currently overclocking a little and want to take that aspect of my system a little closer to the edge, I was a bit concerned (whether justified or not) that my old Thermaltake 485w PSU wouldn't be able to handle the load of an additional 12v pump being added to the system. I immediately decided a second PSU was in order, so I ordered a OCZ 520 Modstream. The most obvious question then came to mind - how do you get both PSU's to turn on with the systems power switch?
The answer is "use a power relay". I puzzled over exactly which one to get because my first thought was to use a PCB-mounted part. Then, the word "soldering" came up, and since I don't have the soldering gene in my DNA (not to mention my troubled past regarding power tools of any description), I decided that I should look for other options. Do you know how many different compact 12VDC relays are available? My biggest concern was getting one that could support an unknown sustained amperage, and that did not require soldering.
I was in the auto parts store with the intention of getting my antfreeze (two different colors, but that's related to my two loops, not this relay thing) when I had an epiphany - why not use an automotive relay? They're inexpensive, durable, small, and easy to find. So I checked out their selection, and I found precisely what I needed - a 12VDC/30A four-spade "normally open" relay for just $3! Even better, it required solderless connectors, so no soldering was involved, which also meant that I wouldn't be visiting the emergency room as a result of this mod.
Before I go further, let's establish some terminology. This mod involves two PSUs, one that connects to your motherboard, and one that doesn't. We'll call the one that does connect to your motherboard the "PRIMARY" PSU. The other one will be called the "SECONDARY" PSU. And so we continue...
Connecting the pins was easy because the schematic for the relay is engraved right on top of it. So, I made two pigtails.
The first one is comprised of a 4-pin male molex connector that utilizes just two of the contacts, along with two wires (and the correct male molex pins of course). To get the right voltage, line the new male connector up to an existing female connector off your PSU (or fan , or whetever), and make a mental note of where you need to put your pigtail wires on the connector. You want to use the 12V side of the connector, so the yellow wire and the black ground wire right next to it are the ones in which you're interested. Crimp a molex pin on one end of each wire, and then a solderless connector onto the opposite end of each wire. Insert the molex pins into the correct holes of the molex connector, and connect the solderless connectors to the correct terminals on the relay. Polarity does NOT matter, since all you're doing is supplying power to a coil in the relay that pulls a switch closed (also inside the relay), causing the other two pins on the relay to short together..
The second pigtail uses part of an ATX extension cable. These come in two flavors - 20-pin and 24-pin. Purchase the one that is compatible with your SECONDARY power supply because it needs to plug into the ATX connector on that PSU (these typically cost about $5). Now, find the end of this extension cable that would actually plug into the motherboard. It will have a locking lever on the center of one of the flat sides of the connector. Take some wire cutters and snip the green wire and an adjacent black wire as close to the female connector as possible. Next, extract any pin AT THE OTHER END OF THE CABLE that is not the green and black ones you cut. This leaves you with a male ATX connector with just two wires. Crimp a solderless connector onto each of the two wires. Finally, push the connectors onto the remaining relay terminals. Once again, polarity doesn't matter.
Now, you're ready to test your creation
1) TURN YOUR SYSTEM OFF.
2) Plug the relay's 4-pin molex connector into an available female connector that's connected to your PRIMARY PSU.
3) Plug the 20/24-pin ATX connector onto the ATX connector from your SECONDARY PSU.
4) IMPORTANT STEP - plug at least one item into the SECONDARY PSU. A fan is sufficient.
5) Make sure your SECONDARY PSU is plugged into a wall outlet, and that the switch is in the ON position.
6) Turn your machine on with the system power switch. If you did it right, both PSU's should power up at almost exactly the same time.
Tools that would come in handy
1) A Molex Pin Extractor
2) An ATX Pin extractor
3) A Molex crimper
4) Wire cutter/stripper
Parts
1) Male molex connector and two pins (you may want to get more than two in case you destroy one in the crimping process)
2) 12-inch ATX extension cable
3) Automotive Relay (12VDC/30A with four spade terminals)
4) Four solderless terminals for 16 to 18-guage wire. I would get a couple more in case you destroy one in the crimping process).
Notes, Warnings, and Disclaimers
1) Check your work.
2) Make sure you correctly identify the pins on the relay. Remember the 12v molex connector pigtail connects to the COIL side of the relay, and the ATX pigtail connects to the SWITCH side of the relay.
3) Check your work.
4) You're dealing with electricity. It can kill you. TYhere's no reason to fear it, but you should respect it's ability to put you 6-feet under when it decides you really hosed something up.
5) Double-check your work.
6) If you hurt or kill yourself, burn down your house, or worse, ruin perfectly good computer components as a direct or indirect result of performing this mod, I won't be held responsible. Afterall, you made the final decision to "throw the switch", as it were.
7) If it looks like I've forgotten something, or if you have a question, don't hestitate to bring it to my attention.
The answer is "use a power relay". I puzzled over exactly which one to get because my first thought was to use a PCB-mounted part. Then, the word "soldering" came up, and since I don't have the soldering gene in my DNA (not to mention my troubled past regarding power tools of any description), I decided that I should look for other options. Do you know how many different compact 12VDC relays are available? My biggest concern was getting one that could support an unknown sustained amperage, and that did not require soldering.
I was in the auto parts store with the intention of getting my antfreeze (two different colors, but that's related to my two loops, not this relay thing) when I had an epiphany - why not use an automotive relay? They're inexpensive, durable, small, and easy to find. So I checked out their selection, and I found precisely what I needed - a 12VDC/30A four-spade "normally open" relay for just $3! Even better, it required solderless connectors, so no soldering was involved, which also meant that I wouldn't be visiting the emergency room as a result of this mod.
Before I go further, let's establish some terminology. This mod involves two PSUs, one that connects to your motherboard, and one that doesn't. We'll call the one that does connect to your motherboard the "PRIMARY" PSU. The other one will be called the "SECONDARY" PSU. And so we continue...
Connecting the pins was easy because the schematic for the relay is engraved right on top of it. So, I made two pigtails.
The first one is comprised of a 4-pin male molex connector that utilizes just two of the contacts, along with two wires (and the correct male molex pins of course). To get the right voltage, line the new male connector up to an existing female connector off your PSU (or fan , or whetever), and make a mental note of where you need to put your pigtail wires on the connector. You want to use the 12V side of the connector, so the yellow wire and the black ground wire right next to it are the ones in which you're interested. Crimp a molex pin on one end of each wire, and then a solderless connector onto the opposite end of each wire. Insert the molex pins into the correct holes of the molex connector, and connect the solderless connectors to the correct terminals on the relay. Polarity does NOT matter, since all you're doing is supplying power to a coil in the relay that pulls a switch closed (also inside the relay), causing the other two pins on the relay to short together..
The second pigtail uses part of an ATX extension cable. These come in two flavors - 20-pin and 24-pin. Purchase the one that is compatible with your SECONDARY power supply because it needs to plug into the ATX connector on that PSU (these typically cost about $5). Now, find the end of this extension cable that would actually plug into the motherboard. It will have a locking lever on the center of one of the flat sides of the connector. Take some wire cutters and snip the green wire and an adjacent black wire as close to the female connector as possible. Next, extract any pin AT THE OTHER END OF THE CABLE that is not the green and black ones you cut. This leaves you with a male ATX connector with just two wires. Crimp a solderless connector onto each of the two wires. Finally, push the connectors onto the remaining relay terminals. Once again, polarity doesn't matter.
Now, you're ready to test your creation
1) TURN YOUR SYSTEM OFF.
2) Plug the relay's 4-pin molex connector into an available female connector that's connected to your PRIMARY PSU.
3) Plug the 20/24-pin ATX connector onto the ATX connector from your SECONDARY PSU.
4) IMPORTANT STEP - plug at least one item into the SECONDARY PSU. A fan is sufficient.
5) Make sure your SECONDARY PSU is plugged into a wall outlet, and that the switch is in the ON position.
6) Turn your machine on with the system power switch. If you did it right, both PSU's should power up at almost exactly the same time.
Tools that would come in handy
1) A Molex Pin Extractor
2) An ATX Pin extractor
3) A Molex crimper
4) Wire cutter/stripper
Parts
1) Male molex connector and two pins (you may want to get more than two in case you destroy one in the crimping process)
2) 12-inch ATX extension cable
3) Automotive Relay (12VDC/30A with four spade terminals)
4) Four solderless terminals for 16 to 18-guage wire. I would get a couple more in case you destroy one in the crimping process).
Notes, Warnings, and Disclaimers
1) Check your work.
2) Make sure you correctly identify the pins on the relay. Remember the 12v molex connector pigtail connects to the COIL side of the relay, and the ATX pigtail connects to the SWITCH side of the relay.
3) Check your work.
4) You're dealing with electricity. It can kill you. TYhere's no reason to fear it, but you should respect it's ability to put you 6-feet under when it decides you really hosed something up.
5) Double-check your work.
6) If you hurt or kill yourself, burn down your house, or worse, ruin perfectly good computer components as a direct or indirect result of performing this mod, I won't be held responsible. Afterall, you made the final decision to "throw the switch", as it were.
7) If it looks like I've forgotten something, or if you have a question, don't hestitate to bring it to my attention.