Zitat von »cc01«

Out of curiosity I have tried a fan controller using a water/air delta instead of water temp only and it works well, although I think I need to fine tune it to my system. Under idle and low loads my system is quieter due to the fans not winding up as much however under load I get regular and pronounced fluctuations of fan speed. Delta doesn't increase beyond 10C and at idle sits around 4 to 5C. I have noticed that using this contoller doesn't work quite as well on hotter days than it does on mild or cooler days, but this is probably due to the inefficiencies of my radiators. I don't have the luxury of numerous and large radiators due to my case being so small, however I've been wanting to upgrade them to something chunkier for some time now ...

That's a problem with how you have set up your sensors ... probably positioning your air sensor.
The outside air temp doesn't change and unless you have a minuscule amount of water in the loop then water temps only change slowly so the delta changes slowly.

Zitat von »Jakusonfire«

That's a problem with how you have set up your sensors ... probably positioning your air sensor.

That's an excellent point. I'd bet his ambient temp sensor is somewhere inside the case or in a similar place that's subject to heat soak and temperature variations.

My air sensor is outside my case and the delta under load actually fluctuates very quickly, which is why I believe my fans are spinning up and down so quickly. I tried a less steep curve as Jeremy suggested and that seemed to work better but it wasn't a dramatic change in terms of the noise. Once I notice the fans spinning up and down it drives me nuts. I'm now using a stepped curve and this works for me in terms of the noise but I think there must be a more elegant solution that also optimises the temperature of the coolant specific to the system. Which brings me to my question ...

Does anyone have experience with setting up the set-point controller?

I experimented a little with that but I have no experience with PID controllers and I couldn't stabilise the controller. I kept getting a massive oscillation of the fans between minimum and maximum output and the controller didn't seem to respond fast enough to a change in the target delta or attempt to stabilise. I used different target delta but the controller would simply adjust itself around the new figure. Adjusting hysteresis would simply delay the controller kicking in before demonstrating the same oscillation. I adjusted the PID values but without any experience it is at best rough guesswork and as yet I'm not sure I completetly understand what parameters each of them adjust. This thread gave me some clues but it is not enough. It is a potentially very useful controller but in the absence of any documentation it may as well not be featured on the Aquaero.

Can anyone with experience suggest a step-by-step method for fine-tuning this controller?

If your calculated dT is changing rapidly, something is amiss with the sensors. Which sensor reading is changing? Water temp or air temp? Both? Where, exactly, is the air temp probe located? Is your water flow rate exceptionally low? There are a ton of possibilities here.

http://en.wikipedia.org/wiki/PID_controller

Back on this subject:
Why would I want to turn my fans off? ... well, why do you need them running constantly???
1) unless the two graphics cards in this rig are pumping out heat, passive cooling works very well with external rads (I have a 720XT Mk4). My sysem is on 24/7, i only need forced air (fans) when doing molecular dynamics calcs or gaming.
2) my airtemp sensor is on the intake side of the fan system. It just tries too hard to match water temp and air temp. I adjusted my control curve to fall to zero volts with a delta T of | 2 |. It may be more adaptive to room temp, but maybe that's the problem. If the room air is 20oC it tries to get within 2oC - really do not need that. If it's 27oC it works less. What happens when the room heats up? Sure, it will work, but maybe overly complex for a simple home/office computer cooling loop. There is a benefit to having the controller based on absolute water temp vs the differential berween it and airtemp if your objective is to control ther water temperature. right?

Right now, my inlet air temp is 26.2 (room is 22 but passive cooling of the rads heats the air near the rads - obviously), water inlet is 26.4, water outlet is 26.3, fans are off. Normal use - i do not need active cooling of rads.