Changing voltages.

[stj]

Re: Changing voltages.

blow in from the side, also you may find that there are a couple of fans at the front right at the bottom - the case sounds familiar.

remember convection - heat rises so extract high, pull in low.

[Spork Schivago]

Re: Changing voltages.

blow in from the side, also you may find that there are a couple of fans at the front right at the bottom - the case sounds familiar.

remember convection - heat rises so extract high, pull in low.

Wouldn't the two top ones (the PSU and the one on the top) create some sort of void? If both are pulling out, wouldn't one of them not get much are at all? With a piece of paper, it seems the very top one doesn't push much air out.


There aren't any fans in the actual front. It seems to be a very cheap case. I guess he bought it off e-Bay. I would have just built a custom one personally. I think it's a custom job that someone else put together. There's a spot in the front for a 120mm fan, it's just not there. Same with the back. A spot for one but nothing. I might actually have a 120mm floating around here somewhere. If it was you, would you add one to the front to get fresh air in there? I believe the unit is in some sort of wooden box, like a cabinet but no door on the front.

I just noticed the side of the case has two extra spots for fans. They're both empty but have the holes drilled through. The breath holes and then the holes for the screws. One is a big one, for maybe a 120mm. That's closest to the bottom. The current fan is in the middle. Then there's a spot for one directly over the CPU. Should I move the middle one to the one above the CPU? Or just leave it where it's at?

[stj]

Re: Changing voltages.

the top fan may just be crap, a lot of pc fans these days are crap so they run silent.
there will not be a void, they will draw air in from other sections of the case.

now putting a fan over the cpu is tricky, you dont want to be blowing air into a fan that is blowing back at you

[Spork Schivago]

Re: Changing voltages.

I gotcha! Thanks Stj. That makes sense.

So, with the CPU fans, they're supposed to blow cold air onto the heatsinks or do they blow hot air away from the heatsinks? I don't remember. I noticed ever since I switched the side fan to blow in, that top fan is blowing a lot more air out. That's good I think.

[stj]

Re: Changing voltages.

most blow cold air onto the sink - BUT NOT ALWAYS.
best to check.

[ChaosLegionnaire]

Re: Changing voltages.

all exhaust huh? yea thats the most common mistake from whoever built the computer. all exhaust actually gives the hottest temperatures! the "wrong" orientation of the fans probably contributed to the cap failures on the board.

once again im going to say that the optimal case fan orientation is all intake and only one exhaust and listen to what stj said about convection. orient the case fans to intake or exhaust in accordance with the laws of physics of convection not your own blardy opinion on what u "think" which way the air will flow!

[Spork Schivago]

Re: Changing voltages.

all exhaust huh? yea thats the most common mistake from whoever built the computer. all exhaust actually gives the hottest temperatures! the "wrong" orientation of the fans probably contributed to the cap failures on the board.

once again im going to say that the optimal case fan orientation is all intake and only one exhaust and listen to what stj said about convection. orient the case fans to intake or exhaust in accordance with the laws of physics of convection not your own blardy opinion on what u "think" which way the air will flow!

It just didn't make sense to me as to why all fans were exhaust fans! I thought the same, they probably contributed a lot to the capacitors failing. The top fan is blowing nice cold air out now. I can feel that. I couldn't feel that before.

Because this unit is going to be in an enclosure, I'm thinking of adding a front 120mm fan so it gets air. It'd be an intake, not exhaust. If I were to add one in the front, would I need to add an exhaust fan in the back? Probably not, right? The PSU and the top fan should be sufficient, I'd think.

[ChaosLegionnaire]

Re: Changing voltages.

be careful where u put the front fan. like stj said u dont want the front fan and the back fan blowing air straight at each other creating an airflow deadzone. where exactly on the front is the fan? is it on the upper or lower front of the case?

[diif]

Re: Changing voltages.

I tend to ignore fitting fans on the side opposite the CPU. They tend to just add to the dust build up on the CPU heatsink which with the stock Intel fans blow down.
I fit one fan on the front at the bottom blowing in and over the drives, and one at the back at the top blowing out. This was with socket 775.

[Spork Schivago]

Re: Changing voltages.

be careful where u put the front fan. like stj said u dont want the front fan and the back fan blowing air straight at each other creating an airflow deadzone. where exactly on the front is the fan? is it on the upper or lower front of the case?

There's no back fan. I added a front fan. This is the layout now.

Front fan - bottom of the front case (very bottom, by the bottom USB ports).
Side fan - middle of the glass window, almost over the RAM
CPU fan - on top the CPU heatsink (about an inch away from the side fan)
PSU fan - inside the PSU
Top Fan - very close to the PSU, just on the very top of the case.

The only intakes are now the Side fan and the Front fan. I added the Front fan as an intake but might remove it if it's too loud. It's from a Dell. It had a 5 pin header. I had to switch the pins around a bit to make it work with the header on this non-Dell motherboard. It's very loud but man, when I was testing it outside the case, it was blowing papers around about 7 feet away. When it turned on, I had to hold onto it good because it was actually moving.

There's no back fan. I guess the PSU fan could be considered a back fan. There's a spot for a 120mm back fan, but it's empty. There's also two more spots for fans on the case. One is for a 120mm, the other one is actually smaller than the 80mm side fan.

[Spork Schivago]

Re: Changing voltages.

I hooked up the Dell fan (after modifying it). It's really loud. There's four pins on it (but it's a five pin header). One is for speed control, one is for sensing the speed, one is for providing voltage (12v), and one is for ground. There's only two connectors on the board. The CPU fan connector is a 4-pin one but is being used for the CPU. The other connector on the board is for a chassis fan but it only has three pins.

I have the fan plugged into the three-pin connector and it works but it's extremely loud. I wanted to know if it'd be wise to use a resistor in line with the 12-volt line. My idea was to put a resistor in there and cut the voltage down a bit, to slow the fan down, thus making it quieter. Would this be a good idea or no? I believe the fan uses 12v, 1.6amps. I was thinking of trying to take it down to 7v and seeing how quieter it'd be.

If it's a good idea, I try using Ohm's law but I think I'm messing something up. I want to know what sized resistor to use. So, I take Ohm's law:

V/I = Resistance
12v / 1.6amps = 7.5 ohms

7.5 ohm is the fan's resistance.

The target voltage is 7v, therefore using Ohm's law again:

V = R * I
7v = 7.5ohm * I

I = V /R
I = 7/7.5 = 0.93 amps

The target current will be 0.93 amps.

Voltage drop across the resistor would be 12v - 7v = 5v.
Using Ohm's law again, I now get:

V = I * R
5v = 0.93amps * R

R = V / I
R = 5v/0.93 = 5.376 ohms

So the target resistance would be 5.376 ohms.

The power dissipated by the resistor would be:

V * I = P
5v * 0.93amps = 4.65 Watt

I'd need a 4.65 watt, 5.376 ohm resistor

Is that right? That doesn't seem right at all!!!

[Spork Schivago]

Re: Changing voltages.

If I can do what I want to do and math is correct, I'd have to use more than one resistor to lower that wattage, wouldn't I? If I were to use 1/4 watt resistors, wouldn't I need 19 of them? 4.65 watt / .25 = 18.6.

5.376 ohm / 18.6 resistors = 0.289 ohm.

I think I'm messing something up here.

[stj]

Re: Changing voltages.

sell the fan and buy several cheaper ones.
if it's that loud and uses that much power then it's a real pro-fan and worth a bit.

[ChaosLegionnaire]

Re: Changing voltages.

I had to switch the pins around a bit to make it work with the header on this non-Dell motherboard. I have the fan plugged into the three-pin connector. I believe the fan uses 12v, 1.6amps.

u what?! please do NOT plug that fan into a mobo fan header!!! mobo fan headers typically have got a 0.6amp current limit. plugging that fan in is going to burn out the mobo fan header or fan power regulator mosfet! use a 4-pin molex to 3-pin fan header converter cable instead to connect the fan directly to the power supply!

[Spork Schivago]

Re: Changing voltages.

u what?! please do NOT plug that fan into a mobo fan header!!! mobo fan headers typically have got a 0.6amp current limit. plugging that fan in is going to burn out the mobo fan header or fan power regulator mosfet! use a 4-pin molex to 3-pin fan header converter cable instead to connect the fan directly to the power supply!

Thank you!!! I'll unplug it. I found a how-to on how to modify these specific Dell fans to plug them directly into the motherboard. That's how I knew which pins to switch. I hate when people write how-to's and post them on the net with false information, especially when that information can destroy something! Thank you for clearing this up for me ChaosLegionnaire.

Is there a way to figure out that 0.6amp current limit? Obviously, the Dell board I pulled this from didn't have that limit but this board does. I believe you're right because the CPU fan is listed as drawing 0.6amp. I don't have one of those 3-pin fan header to molex adapters so I'll probably make one real quick like.

At this point, it sounds like maybe it's just best to remove the fan all together and use nothing in the front. Either that or use my 120mm front case fan, switch them, and run the Dell one off a molex connector instead. That way, the customer won't have to worry about the super loud noise and he'll still get some extra air. I don't mind the noise because I'll know it's cooling real well.

[ChaosLegionnaire]

Re: Changing voltages.

correction, the limit is about 0.7amps. plug in a fan higher than 0.7amps at your own risk (i'm not responsible for fried or dmged mobo).

I don't mind the noise because I'll know it's cooling real well.

u should ask your mrs too if she's fine with the noise from the dell jet engine fan. the fairer sex may not like this kind of noise. i saw and heard one of those dell jet engine fans at a second hand and computer repair store at my local comp mall and its really powerful and pushes a lot of air quite some distance but it also sounded like an a380 or 787 taking off!!! be careful when working inside the computer with that thing on or when holding it while its on. it can actually amputate your finger if it gets caught in there! (i call it a finger chopping fan for good measure!) try adding a fan grill for safety!

[Spork Schivago]

Re: Changing voltages.

correction, the limit is about 0.7amps. plug in a fan higher than 0.7amps at your own risk (i'm not responsible for fried or dmged mobo).

u should ask your mrs too if she's fine with the noise from the dell jet engine fan. the fairer sex may not like this kind of noise. i saw and heard one of those dell jet engine fans at a second hand and computer repair store at my local comp mall and its really powerful and pushes a lot of air quite some distance but it also sounded like an a380 or 787 taking off!!! be careful when working inside the computer with that thing on or when holding it while its on. it can actually amputate your finger if it gets caught in there! (i call it a finger chopping fan for good measure!) try adding a fan grill for safety!

I just so happen to have a fan grill! Good call on the Mrs part! Never thought of that. And seeing how it'd be running 24/7, that might not be the best idea. Specially since we have a little one on the way. I was actually afraid when I was holding it that it could chop my finger off. Then I thought, nah, it's just in my head. But I held onto it real good. I was really impressed with how much air this thing pushes. When I turned it on and was holding it, my hand literally went back a bit. What the heck does Dell use these for? I think cooling the CPU if I'm not mistaken. I wasn't really paying attention where I got it from. I got a few of them though. The thing is a beast!

[dmill89]

Re: Changing voltages.

What the heck does Dell use these for? I think cooling the CPU if I'm not mistaken.

Mostly servers and workstations. My Dell PowerEdge 840 tower server has one, it is the only fan in the case except for the on in the PSU, it has a duct over the CPU heatsink and functions as both the CPU and rear exhaust fan, (there is a spot for a front case intake fan as well, but only models with SAS cards got that). The fan controller does a pretty good job of keeping it relatively quiet (you can hear it but it is not overwhelmingly loud) most of the time, but on boot up (it runs at full-speed for a few secs. until the fan controller kicks in) and heavy load it does indeed do it's best to mimic a jet engine.

[stj]

Re: Changing voltages.

is this dell fan a 3-blade unit made by Nidec?

[Spork Schivago]

Re: Changing voltages.

is this dell fan a 3-blade unit made by Nidec?

No, it is not. It has 7-blades and it's made by Minebea-Matsushita. I have a few of these types. They're in a lot of the older Dells I have. Here's a link to the one I have (but mine doesn't have that grill that the one here has).

https://www.dreamhardware.com/fan-5w...FckehgodduMEug

Even though the one I linked to uses the same amperage (1.30amp), for some reason, it has the standard three-pin header it looks like, instead of the Dell custom 5-pin.

I bet a lot of people are probably upset after buying that. They probably thought like I thought, that it could just be plugged into the motherboards header. Drawing the 1.30amp probably ruined their board.