Need a Reliable PSU

[philipma1957]

If we populate the 5V buck circuit you probably could by using the voltage differential there. We rate the circuit at 2A for safety, but the buck controller is rated for 3A max. If you wanted, by changing three parts on the circuit I could probably make it output 7V constant without having to rely on differentials. I can probably test that out on Monday.

Do you know the actual power draw of the S5's fan at lower speed? If it's 3A at 12V it's probably a fair bit less than that when ramped down.

I can check that for you today. -------  7 volts stock fan draws 1 amp



  I ended up running delta fans on my s-5's  I have an evga 1300 g2.

 I plugged in a 4 pin molex tapped 2 wires to get 7.18 volts  and the 2 delt's run great.

If you can figure a way to draw 7 volts the stock fan on an s-5 runs much more bearable  the nasty sounding  pitch drops off.

the stock fan will cool well enough at 7 volts to run the s-5 at 325 -362 freq   depends on the rooms temp.

this is the final fan mod to the s-5

https://bitcointalk.org/index.php?topic=927941.0


if you can get your psu to do 7 volts at 3 amps .   the stock fan should work well.

see this has 2x    4 pin  jacks   so if you cut this off the plug you have 20x    4 pin jacks for 1 usd each,  if you sold this wire with the break out board so that it was pre wired for 7 volts allowing the crazy loud oem fan on the s-5 to plug in the fan would run at a constant speed and be more endurable for the s-5 operator.


http://www.ebay.com/itm/10pcs-PC-Cooling-Fan-4-Pin-to-2x-4pin-3pin-PWM-Convert-Connector-Extension-Cable-/121088267930?pt=US_Memory_Chipset_Cooling&hash=item1c316c569a

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[sidehack]

So do you actually need 3A at 7V if the fan only pulls 1A? I'm not sure how well our 5V buck will handle sinking from a 12V source (I've never tested its ability to do that) but if it works at rated current, I could get you a comfortable 2A at 7V. Pulling from two wires on your ATX PSU is pulling 12V current sunk into a 5V source, so a net 7V differential. It'd be the same thing. I'll test it when I get to work tomorrow and see how the boards behave pushing some big fans on the 7V differential - I have some 3.3A 4-wire fans that should simulate your loads adequately.

Another option for S5, if you want to be able to use the PWM line on the fan, is to use the fan headers on our DPS-2000BB boards, which are built to PWM speed-control 4-wire server fans. That'd give you a full adjustable range instead of "whatever speed it gets at 7V" as the only setpoint.

[philipma1957]

So do you actually need 3A at 7V if the fan only pulls 1A? I'm not sure how well our 5V buck will handle sinking from a 12V source (I've never tested its ability to do that) but if it works at rated current, I could get you a comfortable 2A at 7V. Pulling from two wires on your ATX PSU is pulling 12V current sunk into a 5V source, so a net 7V differential. It'd be the same thing. I'll test it when I get to work tomorrow and see how the boards behave pushing some big fans on the 7V differential - I have some 3.3A 4-wire fans that should simulate your loads adequately.

Another option for S5, if you want to be able to use the PWM line on the fan, is to use the fan headers on our DPS-2000BB boards, which are built to PWM speed-control 4-wire server fans. That'd give you a full adjustable range instead of "whatever speed it gets at 7V" as the only setpoint.

that is a damn good feature.  2 s-5's run easy on that psu.

[sidehack]

You'd lose probably 2% efficiency but it'd handle three. Technically it should handle 4 but the PSU would be way over spec.

We thought about building a small standalone circuit of just the PWM fan control, but I don't know how many people would use it.

[sidehack]

So I just checked, and the 5V line on our boards don't like to sink. I'm not terribly surprised by this. The next step was converting the 5V regulator to a 7V, which with a single part swap of a part I already had I talked it into outputting 6.90V and it's currently feeding a fan which I measured to pull 1.3A at 7V even. So I'm going to call that a win.

So if anyone's interested in a 750W server-grade PSU with a 7V rail for running a quieter fan, I can supply a full kit (PSU, interface board, 4x 18" 16AWG PCIe cables) for $55 plus shipping.

[philipma1957]

So I just checked, and the 5V line on our boards don't like to sink. I'm not terribly surprised by this. The next step was converting the 5V regulator to a 7V, which with a single part swap of a part I already had I talked it into outputting 6.90V and it's currently feeding a fan which I measured to pull 1.3A at 7V even. So I'm going to call that a win.

So if anyone's interested in a 750W server-grade PSU with a 7V rail for running a quieter fan, I can supply a full kit (PSU, interface board, 4x 18" 16AWG PCIe cables) for $55 plus shipping.

yeah that will work well.

my s-5 is running with 2 deltas using 7.18 volts

 the stock oem fan will do the job at 6.9 volts.

[sidehack]

I can set the voltage to anywhere in that range, just gonna need a few days to get the right part. I happened to have a strip of resistors that are almost spot-on so that's what I tested with.