How to stop sag?

[H20Cool]

Ok, this is kind of hard to describe, but I'll do my best. I just recently setup water cooling in my rig, the cooling performance is great and I'm quite happy with it, with the exception of an annoying "voltage fluctution dip sound" coming from my pump. If that makes any sense? This is where it gets a little difficult to describe. The pump noise is fine, per say. It makes a slightly audible high pitched sort of sound, but it's constant so it's not annoying. What does get annoying, is everytime I use a paint brush in PSP8 or copy some files or access something; basically everytime the PC has to do some work, the pump sound sort of dips off, I would assume from the slight current sag caused by other components wrestling for juice. I'm using a 3 month old OCZ modstream that's working perfectly so I don't think there is a problem with the PSU. It just seems to be a normal current fluctuation (like when you turn on a hair dryer and it makes the lights on that circuit dim slightly). Unfortunately though, it ends up causing the pump to get quite for a certain amount of time (depending on what's being done), then it goes back to the high pitched sound, once the cpu/hardrive work is done. I can handle pretty much any noise from my computer (as long as it's not obnoxious) but variances like this drive me nuts.

So I guess my question is, short of using a dedicated 12V power supply for my pump, what can be done to combat this? Would some type of capacitor between the pump and PSU help? Anybody with some electrical knowledge that has any idea what I can do about this, please reply. Thanks

 

[Operandi]

You really have two options, add dedicated 12v source for the pump like you mentioned or change the PSU. The OCZ may be working perfectly fine but that doesn?t mean the pump or one of the other components isn't interacting with the PSU. Can you try running the pump with a separate PSU and the rest of the system with the OCZ?

 

[H20Cool]

I'd rather not go with a separate PSU to power the pump. By having another PSU in the case or worse, outside the case, things start to get cluttered.

So I was thinking about two alternate options. One would be to get a fan controller (rheostat) that can handle 24W (2A@12V) and use it to reduce the pumps voltage just enough to get rid of the high pitched whine entirely, so I won't notice the sag. The other option would be to use a 12V adaptor with a 2A rating, this would require that I wire up a relay so the pump turns on with the PC.

I do know capacitors are comonly used for preventing voltage fluctuations or surges, by acting similar to a battery. But I don't know enough about them to decide exactly what to buy, how many farads, etc.

In the mean time, I think I'll look for a 24w rheostat and see if I can get rid of the whine entirely, that would be the best option really. As long as the pump volatge is high enough that I don't loose to much in the way of flow and pressure.

 

[HardWarrior]

You could try isolating the pump on it's own loom. What are the specifics of your PSU? In general, if I was in your position, I'd be very concerned with the broader implications of what else might be sagging.

 

[H20Cool]

The PSU is an OCZ Modstream 520W with the following specs: Max. output current: +3.3V @ 28A, +5V @ 52A, +12V @ 28A. The pump only draws 2A from the +12V supply (24 Watts) and it is on its own loom. So again, I don't think there are any implications of having the pump run off the OCZ PSU, other than the annoyance. I just think that the type of sound that the pump produces is subject to the slightest of voltage fluctuations and as far as I know, slight (millivolts) voltage fluctuations during various load requirements are normal for any power supply. I have been checking the voltages through MBM and everything seems to be ok with the PSU, I've had absolutely no hardware problems, blue screens, or spontaneous reboots, so I'm pretty sure the PSU is working fine. I'm heading over to Radioshack today to see if I can find a 24W rheostat, so I can dial the pump in at the best trade off between noise and performance. I'll try that and see what happens.