PWM pump control questions (issues)

[Erik765]

Hello,

I've recently noticed the CPU fan header on my motherboard has stopped effecting my pump speed as it did in the past. I had a brand new pump in the box (thinking it may have been the pump). Swapped them out, same result. It runs at full speed all the time (even though it shouldn't based off my BIOS settings).

My pump is a MCP 35X http://www.performance-pcs.com/catalog/index.php?main_page=product_info&products_id=29201 and has built in PWM control.

I researched some PWM diagrams to find out a simple way to just add a manual knob control to it and came across this site: http://www.bit-tech.net/modding/2001/12/03/pwm_fan_controller/1

I noticed on the diagram, they just use a 10k rheostat so I figured, hey, I'll just run down to radio shack and grab a 10k rheostat and hook it up to my pwm lines... http://www.radioshack.com/product/index.jsp?productId=2062299 Well, it does work (I'm sure all you electrical guys are laughing at this point). The pump acts essentially the same as if I were to just short the two wires (green and blue), it slows down to about half speed. turning the rheostat knob doesn't effect the speed at all.

Anyone know what I may be doing wrong here? (I hate electrical stuff).

What if I just hooked it up to the power leads on the pump? How would that work though with 2 wires and only 3 terminals on the rheostat?

My water-cooled box isn't any quieter than my old air-cooled system with my pump running at full speed all the time now

Thanks in advance for any tips!

EDIT: Hmm, looks like I got a 25 ohm rheostat when what was used in the diagram was a 10k potentiometer. Will this make a difference at all though? The problem is this pump runs at 18 watts and the potentiometers I saw at the shack said like .5 watts or something (for speakers and such). But will that matter since I'm just on the PWM leads anyway?

How the heck to people normally slow down their pumps for a quieter system?

 

[Bobnova]

This is how you control a PWM pump/fan correctly: http://www.overclockers.com/pwm-fan-controller

Cheap and easy to build, and very satisfying to control fans/pumps with as you built it yourself

 

[Erik765]

Thank you.

Looks like that only works for 5v though and not 12v

And remember: This circuit uses 5v, NOT 12v.

Any tips for making it work with 12v?

 

[Bobnova]

PWM control circuits are all 5v, even when controlling 12v devices like fans and pumps.

 

[ssjwizard]

It would also be helpful to know what motherboard you have this connected to. Have you made any changes in the BIOS lately? Have you adjusted windows power options lately?
Its very possible that you changed the control mode on your fan header by accident, or disabled the mobo function that adjusts fanspeed(cool 'n quiet for example). Or you may have changed the cooling profile by adjusting windows power options.

Just some ideas.

 

[Erik765]

PWM control circuits are all 5v

Thank you.

My thought though is, if the pump already has PWM wires on it and has a PWM setup inside it, wouldn't a potentiometer or rheostat work to control its speed when attached to the PWM leads?

It would also be helpful to know what motherboard you have this connected to.

EVGA P55 FTW

I do not see any specific power settings in Windows that mention the CPU fan specifically. I don't have any other third party software installed (never needed to).

Here is a pic of the BIOS setting that has always worked in the past



Thanks again for your help. Best bet option would be to get it working from the BIOS again, but if not, I can build that circuit and turn it up when needed manually.

I'd like to have my pump last longer (and be quieter) so I need to figure something out one way or the other.

 

[ssjwizard]

I wish that my mobos had options that detailed for the fan control.

Try either raising the max fan temp OR lowering the max fan speed and see if either of those effects it.

The reason a pot on your PWM line wont work has to do with the nature of PWM. Its a signal not a static voltage.

 

[Elfie]

Check that the PWM connector hasn't come loose from the connector, mine used to be prone to doing that at the slightest touch.

Does EVGA supply any software that'll allow PWM control for your motherboard? You may be able to configure SpeedFan to do it if not.