Any way to power one 4 pin (molex) device from TWO PSU's?

Zarathustra[H]

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So, I might be taking advantage of the fact that my Corsair 1000D can house two systems, one EATX and one MiniITX in the same case.

Only problem is they will be sharing a water loop and fans.

I can't guarantee in my use case that one system will always be powered on when the other is on. Sometimes both will be powered on, but sometimes only one or the other will be powered on.

Is there a way to use some sort of 5v and 12v automatic transfer switch to power the same device (fan controller, pump & fans) from two different PSU's, having it just pull power from whichever one happens to be powered on?

Appreciate any thoughts!
 
I looked around a bit and didn't see anything obvious like a dual power supply joiner.
Depending on how far you are willing to DIY it you could get a couple of 4-pin molex extenders and a couple of high current diodes (15A is likely overkill, maybe something smaller would work) and then Y them together with some solder and heat shrink.
The diodes will prevent back feeding of one power supply into the other and as long as one supply is on the male 4-pin will get power. Depending on current draw you may drop half a volt across the diodes but for something like fans it should be fine.

Molex Combiner Diagram.png
 
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I looked around a bit and didn't see anything obvious like a dual power supply joiner.
Depending on how far you are willing to DIY it you could get a couple of 4-pin molex extenders and a couple of high current diodes (15A is likely overkill, maybe something smaller would work) and then Y them together with some solder and heat shrink.
The diodes will prevent back feeding of one power supply into the other and as long as one supply is on the male 4-pin will get power. Depending on current draw you may drop half a volt across the diodes but for something like fans it should be fine.

View attachment 558327


Thanks for the idea!

Is there a way to limit the voltage drop across the diodes? Better diodes or something?

Or maybe I can just use a couple of those cheap step-up boards from ebay to pull the voltage back up on the other side...

You know, something like this.
 
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You probably could go that route to step up the voltage but at that point the design is starting to get complicated.
Maybe instead you can purchase a 12V DPDT relay and wire it up like the below.

If PSU 2 is off, the relay is not activated and the fans run off PSU 1.
If PSU 2 is on, the relay is activated and the fans run off PSU 2.
Either way, as long as one PSU is powered the fans are powered.

The cooling loop will be momentarily be shut off when PSU 2 is turned on and off and the relay flips positions.

1679466467205.png
 
Thanks for the idea!

Is there a way to limit the voltage drop across the diodes? Better diodes or something?

Or maybe I can just use a couple of those cheap step-up boards from ebay to pull the voltage back up on the other side...

You know, something like this.
Germanium diodes have a smaller voltage drop, but you will need to be careful about power draw.

Some fast switching shokky (sp) diodes will do it.

What is the power draw of the pump and fans? I may have some other ideas
 
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Germanium diodes have a smaller voltage drop, but you will need to be careful about power draw.

Some fast switching shokky (sp) diodes will do it.

What is the power draw of the pump and fans? I may have some other ideas

I'm not sure how close to the limit of a single 4-pin accessory power connector I am going to get. There doesn't seem to be an official spec. The 4pin connector itself is rated up to 13 amps, but considering most of them use 18ga wire, this seems unrealistic. I ahve seen some sites suggest 5 amps per cable to be on the safe side, but I ahve also seen fan controllers rated for 7 amps over the 12v, so 84w max over 12v, and 35W max over 5v seems likely.

The biggest draw is going to be the two D5 pumps, which are 24w each an only draw on the 12v line.

Then there is going to be the Aquacomputer Aquaero 6 fan controller. Unfortunately the specs don't tell me how much power it draws, only how much power it is able to pass through to fans. I can't imagine it draws more than like 4-6 watts though.

Then there are probably going to be ~10 low speed 120mm and 140mm fans, at ~0.15 amps max each, so that's another 18w.

So my educated guess is that I am looking at a grand total of ~72 watts at most. The overwhelming majority of that load will be on the 12v line, but I will still need the 5v, unless I just run one wire and step it down from the 12 to make it simpler. (though this may inadvertently make it more complex)
 
Your startup current draw is gonna be high, not an issue much for the connector but whatever means you use for switching should be able to handle that as well. FETs can function as a diode as well and tend to have a lower voltage drop. Bit more ESD sensitive on the gates though so be aware of that. The mentioned relay config should work.
 
Your startup current draw is gonna be high, not an issue much for the connector but whatever means you use for switching should be able to handle that as well. FETs can function as a diode as well and tend to have a lower voltage drop. Bit more ESD sensitive on the gates though so be aware of that. The mentioned relay config should work.

You think it would be possible to solder in a small cap to avoid dropping power (and rebooting the Aquaero) during the fraction of a second it takes the relay to switch?
 
You think it would be possible to solder in a small cap to avoid dropping power (and rebooting the Aquaero) during the fraction of a second it takes the relay to switch?
It would likely be something a bit larger depending on the switchover time. ~12,000uF will give you about 5milliseconds until 11V at your wattage (correct me if my math is wrong). But that might be good enough. The controller should also have its own capacitance that will help. Might be a try and see kinda thing.
 
It would likely be something a bit larger depending on the switchover time. ~12,000uF will give you about 5milliseconds until 11V at your wattage (correct me if my math is wrong). But that might be good enough. The controller should also have its own capacitance that will help. Might be a try and see kinda thing.

I just found this product over on MiniBox.com that might be just want I need.

https://www.mini-box.com/Y-PWR-Hot-Swap-Load-Sharing-Controller

$29 seems a little hefty, especially since I'd need two (one for 12v one for 5v) but there is a little peace of mind involved with using a product actually designed by somoene who knows what they are doing :p
 
I just found this product over on MiniBox.com that might be just want I need.

https://www.mini-box.com/Y-PWR-Hot-Swap-Load-Sharing-Controller

$29 seems a little hefty, especially since I'd need two (one for 12v one for 5v) but there is a little peace of mind involved with using a product actually designed by somoene who knows what they are doing :p
Yea that looks like that should do what you want. Price isnt terrible though, do gotta pay for peoples time since it is saving yours :p
 
I'm not sure how close to the limit of a single 4-pin accessory power connector I am going to get. There doesn't seem to be an official spec. The 4pin connector itself is rated up to 13 amps, but considering most of them use 18ga wire, this seems unrealistic. I ahve seen some sites suggest 5 amps per cable to be on the safe side, but I ahve also seen fan controllers rated for 7 amps over the 12v, so 84w max over 12v, and 35W max over 5v seems likely.

The biggest draw is going to be the two D5 pumps, which are 24w each an only draw on the 12v line.

Then there is going to be the Aquacomputer Aquaero 6 fan controller. Unfortunately the specs don't tell me how much power it draws, only how much power it is able to pass through to fans. I can't imagine it draws more than like 4-6 watts though.

Then there are probably going to be ~10 low speed 120mm and 140mm fans, at ~0.15 amps max each, so that's another 18w.

So my educated guess is that I am looking at a grand total of ~72 watts at most. The overwhelming majority of that load will be on the 12v line, but I will still need the 5v, unless I just run one wire and step it down from the 12 to make it simpler. (though this may inadvertently make it more complex)

I have a simple solution for you...

https://www.ebay.com/itm/165640843092

These units are plentiful and cheap, essentially they need 5v and gnd on the relay to trigger it.

So you wire the 5v line up on one power supply, and run both 12v line and gnd on separate relays. (scuse the potato drawing.. but you get the idea)

1679550449430.png


If you need more power, double the relays and have two connectors/inputs
 
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I have a simple solution for you...

https://www.ebay.com/itm/165640843092

These units are plentiful and cheap, essentially they need 5v and gnd on the relay to trigger it.

So you wire the 5v line up on one power supply, and run both 12v line and gnd on separate relays. (scuse the potato drawing.. but you get the idea)

View attachment 558684

If you need more power, double the relays and have two connectors/inputs
No, this doesnt work. You need to isolate the power rails from eachother so when both supplies aren't up they are fighting eachother and going into an oscillation. You would also be better leaving ground connected because you don't want scenarios with voltage presence and ground not.
 
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I still think the single relay option in post 4 is best for cost and simplicity. If cost isn't a concern a designed part like that YPWR is a great solution.
 
No, this doesnt work. You need to isolate the power rails from eachother so when both supplies aren't up they are fighting eachother and going into an oscillation. You would also be better leaving ground connected because you don't want scenarios with voltage presence and ground not.
They are isolated in that instance...
 
$29 seems a little hefty, especially since I'd need two (one for 12v one for 5v) but there is a little peace of mind involved with using a product actually designed by somoene who knows what they are doing :p
*Has two high end systems on a custom loop in a $500+ case*

"I dunno guys, $60 seems awfully spendy." :ROFLMAO:
 
I still think the single relay option in post 4 is best for cost and simplicity. If cost isn't a concern a designed part like that YPWR is a great solution.
With 75W load - I would not recommend 1 relay.
 
*Has two high end systems on a custom loop in a $500+ case*

"I dunno guys, $60 seems awfully spendy." :ROFLMAO:

I don't mind spending money on things I deem "worth it".

I've come to expect something that is mass produced to usually be cheaper than I could do it myself. $29 for something that's a few cents in parts and a very simple design just seems off.
 
Late to the party, and you may have already found a solution, but what about a 3rd power supply just for pumps and fans? Then you just have it switch on whenever either power supply is on.
 
So, I might be taking advantage of the fact that my Corsair 1000D can house two systems, one EATX and one MiniITX in the same case.

Only problem is they will be sharing a water loop and fans.

I can't guarantee in my use case that one system will always be powered on when the other is on. Sometimes both will be powered on, but sometimes only one or the other will be powered on.

Is there a way to use some sort of 5v and 12v automatic transfer switch to power the same device (fan controller, pump & fans) from two different PSU's, having it just pull power from whichever one happens to be powered on?

Appreciate any thoughts!
Did you already ask Aquacomputer support as well as the online forums? If no answer in the English forum post in the appropriate German forum. If I recall correctly the Aquaero 6 will power up both D5 pumps. You use the fan headers if you are using PWM. Using the active splittty board should allow you to power up quite a lot of fans. The only Aquaero version being sold now is the LT version. However it is possible to add the screen of you need it through AC support.
 
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