Search found 135 matches

by pcy
Fri Jan 05, 2007 8:32 am
Forum: Fans and Control
Topic: The 4-pin PWM fan specification document
Replies: 26
Views: 58711

Hi,


You mean you want to see a pic, or you want me to send you one?



Peter
by pcy
Fri Jan 05, 2007 7:34 am
Forum: Fans and Control
Topic: How Low Can You Go? (rpm-wise)
Replies: 20
Views: 5598

Hi,


The computers I build are used for recording music.

If I can hear it when everything else in the room is switched off it's too loud.


But "inaudible" means that you cannot hear it at all. That no the same as just quiet, or even so quiet that you don't notice it.




Peter
by pcy
Fri Jan 05, 2007 5:35 am
Forum: Fans and Control
Topic: How Low Can You Go? (rpm-wise)
Replies: 20
Views: 5598

Hi,

I've got some 140mm fans down to 450rpm.


Even inside a case, and even at 600rpm or less, I have yet to find a genuinly inaudible fan.

If the room itself is sufficiently quiet...



Peter
by pcy
Thu Jan 04, 2007 12:22 pm
Forum: Fans and Control
Topic: The 4-pin PWM fan specification document
Replies: 26
Views: 58711

Hi, We have tested the prototypes, and we are using them on machines that I build, while we organize larger volume production. It is a PWM to DC converter. The input to the circuit is PWM (4 pin) and the output is ordinary 3pin with the power voltage between 3V and 12V depending the PWM input. There...
by pcy
Wed Jan 03, 2007 1:23 pm
Forum: Fans and Control
Topic: The 4-pin PWM fan specification document
Replies: 26
Views: 58711

Hi,


That works in principle, but in practice yoyu won't get enough amplification from a single transistor cct.


I've had one designed by an electronics engineer, and we ended up using 4 transistors to get it to work smoothly and provide some adjustement etc.



Peter
by pcy
Wed Jan 03, 2007 1:19 pm
Forum: Deals, Vendors and Classifieds
Topic: FS: PWM->analog Voltage Controller Circuit for pumps/fans
Replies: 17
Views: 19561

Hi,

I have a similar product. So far we have only built protptypes, but they work fine controlling varuous 3 pin fans using the PWM output fro an Intel DP965LT mobo.


I was thinbking of making them available for about £5 - $9.50 plus postage...



Peter
by pcy
Tue Jan 02, 2007 6:57 am
Forum: Fans and Control
Topic: "250mm" fans vs 120mm: the physics, math, tables &
Replies: 13
Views: 3931

Hi, I completely agree that thre must be tip vortices and that the flow cannot ne entirely laminar. But by "laminar flow" I meant tht the flow over the baldes was largly laminar, with turbulence confined to the boundary layer and teh tip vortices. That's certaily what you get on the sail of a yacht,...
by pcy
Tue Jan 02, 2007 5:12 am
Forum: Fans and Control
Topic: "250mm" fans vs 120mm: the physics, math, tables &
Replies: 13
Views: 3931

Hi, Excellent, thanks. So that's energy proportional to specific gravity of air times velocity cubed. Seems intuitive now, and if experimental evidence confirm it as well... I'm still concernrd that the noise ~ power bit is only true within a limited envelope of conditions - something like subsonic ...
by pcy
Mon Jan 01, 2007 3:24 pm
Forum: Fans and Control
Topic: "250mm" fans vs 120mm: the physics, math, tables &
Replies: 13
Views: 3931

Hi, I'm simply trying to understand. There is no way that energy is proportional to mass times velocity cubed because energy it is in fact proportional to mass times velocity squared. The mass of the air colum may itself be proportional to the velocity, and I'm intirely happy with the idea that tota...
by pcy
Mon Jan 01, 2007 2:47 am
Forum: Fans and Control
Topic: "250mm" fans vs 120mm: the physics, math, tables &
Replies: 13
Views: 3931

Hi, 1. The energy of a moving column of air is equal to M*V^3, where M is the mass of air and V is its velocity. 2. Acoustic noise is proportional to the energy. 1. I'd be prepared to beleive that the energy was SxV*3 (where S is the specific graviity of air) as the mass of air passing through the f...
by pcy
Fri Dec 29, 2006 6:13 am
Forum: Fans and Control
Topic: Restriction?
Replies: 20
Views: 5264

Hi,

I agree that if there is no detectable change in CPU temp the effect of the grill must be neglible in that particualt case.


But I'm also saying that your results are not necessarily insonsistnt with Mike Cs, if his 20% reduction in airflow was taken in free air at 12V.




Peter
by pcy
Fri Dec 29, 2006 2:41 am
Forum: Fans and Control
Topic: Restriction?
Replies: 20
Views: 5264

Hi, I'd have to say that that's a valid, but very insensitive test. The probelm is that the CPU temp is only reported to 1C. Let's look at the numbers: The CPU generates a constant amount of heat, so the total rise in the air temp flowing through the cooler multiplied by the air flow through the coo...
by pcy
Wed Dec 27, 2006 7:57 am
Forum: Fans and Control
Topic: blowers vs fans
Replies: 7
Views: 2516

HI,

And a Zlman 7000 scarcely qualifies a heavy competition.


Peter
by pcy
Wed Dec 27, 2006 4:58 am
Forum: Fans and Control
Topic: Calling All Good Fans!
Replies: 143
Views: 282541

Hi, I've just recieved a batch of GlobalWin 120mm fans with ceramic bearings. The bearings are suitable for high(er) temperature work - i.e CPU cooling fans. There is definately much less noise coming from the bearings compared to say the Asaka Amber; and also much less commutator vibration at low s...
by pcy
Wed Dec 27, 2006 4:24 am
Forum: Fans and Control
Topic: blowers vs fans
Replies: 7
Views: 2516

Hi,

Very helpful - thanks.


Peter
by pcy
Wed Dec 27, 2006 3:04 am
Forum: Fans and Control
Topic: blowers vs fans
Replies: 7
Views: 2516

Hi, Yes... I too am unclear about this distinction between a blower and a fan. However, the CPU fan is being used to push air through the CPU heatsink, which is in fact a pretty substantial obstacle to airflow. The actual airflow is way down on the free flow CFM the maufacturere would quote; and the...
by pcy
Wed Dec 27, 2006 3:00 am
Forum: Fans and Control
Topic: Do you really need an exhaust fan
Replies: 7
Views: 2115

Hi, As Bluefront suggests, it all depends on the case layout and airflow design. The important thing is that hot air is coming off the CPU cooler; and you have to have some means to make sure that a good proportion of that hot air goes out of the case. Otherwise the inside of the case wil just get h...
by pcy
Wed Dec 27, 2006 1:58 am
Forum: Fans and Control
Topic: Restriction?
Replies: 20
Views: 5264

Hi, Could we possibly extend this to measuring the resistance or actual airflow through a CPU heatsink. I'm not certain that I beleive the manufacturers quoted figures fro CFM: but even if I did they are CFM in free air; and the Heatsink represents a massive resistance to airflow. The actual aiflow ...
by pcy
Tue Dec 26, 2006 11:55 am
Forum: Fans and Control
Topic: Are 2 fans noisier than 1 blowing the same CFM?
Replies: 64
Views: 162567

Hi,


well... 50 x log10 0.5 is around 15.



So halving the speed of a fan should reduce the dB by 15. That's more in line with my subjective experience....



Peter
by pcy
Tue Dec 26, 2006 4:22 am
Forum: Fans and Control
Topic: Are 2 fans noisier than 1 blowing the same CFM?
Replies: 64
Views: 162567

Hi, I think you need to know the total noise output of the fans to be certain. You will certainly end up with more CFM using 2 @ 5V rather than 1 @7V: just over 40% more in fact. In dBA terms you have both a reduction and an increase, so the net effect is hard to calculate. Each fan at 5V will produ...
by pcy
Tue Dec 26, 2006 3:09 am
Forum: Fans and Control
Topic: 140mm fan experience and where to buy?
Replies: 18
Views: 8674

Hi, I'm also using the AeroCool Sreamliner, but my experience is different. It moves slightly less air than many 120mm fans - true: but it runs at 1000 rpm max, and produces much less niose. Mine start at below 4V and will run smoothly down to about 470 rpm. I get the impression that they are less s...
by pcy
Tue Aug 01, 2006 12:11 am
Forum: The Silent Front
Topic: Isolating hot components from each other - is there a point?
Replies: 28
Views: 12492

Hi Isaac, Have you tried running the machine cooled by the Zalman VGA cooler at 100% CPU for a few days. Nope. I'm never going to run it at 100% CPU for any significant length of time. If I want computing power, I'm not going to use a mere 564mhz Pentium III when I've got a 2.4Ghz Pentium IV around....
by pcy
Mon Jul 31, 2006 1:10 pm
Forum: The Silent Front
Topic: Isolating hot components from each other - is there a point?
Replies: 28
Views: 12492

Hi Isaac, Yes just one minimum speed 80mm fan. But none of my systems are anywhere near as powerful as yours! I only do shoestring budget computers. I recently got my hands on some cheap Sempron 3100 combos--those were massive upgrades for me. I just had a look at the stuff you posted in the general...
by pcy
Mon Jul 31, 2006 11:12 am
Forum: The Silent Front
Topic: Isolating hot components from each other - is there a point?
Replies: 28
Views: 12492

Hi Isacc, Yes... that limit was implicit im my argument. It remains true that if anybody made larger fans that would start up at all under suitable voltages you wouold still get less noise from the bigger/slower route. There is probably some other limit here as well.... I'm surprised/impressed at wh...
by pcy
Mon Jul 31, 2006 9:54 am
Forum: The Silent Front
Topic: Isolating hot components from each other - is there a point?
Replies: 28
Views: 12492

Hi, Surely the reason for isolating the components is that they all have different cooling requirements that vary independently of one another. For example, a hard disk must be kept at a much lower temperature than for example a CPU, but conversely needs much less airflow to keep it at that temperat...
by pcy
Mon Jul 31, 2006 9:40 am
Forum: The Silent Front
Topic: Isolating hot components from each other - is there a point?
Replies: 28
Views: 12492

Hi Bluefront, "Typically this will reduce noise levels by 10 times"........just where do you get that figure? But you miss the point......with proper design/airflow, you can get the same cooling, at the same noise level, with fewer fans, the minimum being one. dB is roughly proportional to CFM for a...
by pcy
Mon Jul 31, 2006 3:48 am
Forum: The Silent Front
Topic: Isolating hot components from each other - is there a point?
Replies: 28
Views: 12492

Hi, matter of opinion....more fans equal more cost, more trouble to mount, more chances for bearing noise, more difficulty to filter, more chances for failure, and so on. We have yet to see the perfect airflow in a case which results in the quietest/coolest computer. But IMHO, that perfect airflow w...
by pcy
Sun Jul 30, 2006 3:09 am
Forum: The Silent Front
Topic: Isolating hot components from each other - is there a point?
Replies: 28
Views: 12492

Hi, This question has no answer. There is no single right way. Seriouly.... because the devil is in the detail. The best arrangement depends entirely on exactly how much haet each component happens to create, and how hot it can run. Just consider the following simple question. If you have a separate...
by pcy
Thu Jul 27, 2006 8:01 am
Forum: The Silent Front
Topic: Less airflow equals cooler temps.....
Replies: 21
Views: 8376

But I think that you're right that the BTX design exauasts the hot air from the output side of the CPU cooler straight out of the case. It's pretty obvious that you don't want to allow the hottest air to re-circualte... That's pretty obvious to everybody except the people making 120W CPUs. BTX feed...
by pcy
Thu Jul 27, 2006 5:04 am
Forum: The Silent Front
Topic: Less airflow equals cooler temps.....
Replies: 21
Views: 8376

Hi, The case is 7" by 18" by 22". That's about as small as I can make it and still get the three internal 120mm case fans in. We've worked on the mufflers since those details were posted. The best I've had has been an X2 4800 plus 2 300GB HD and a fanless nVidia7300 running flat out (2 copies of Pri...