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Dear God, What Have I done!!!!!
- Thread starter Empireking01
- Start date
- Joined
- Aug 12, 2003
- Location
- West Virginia
A quick ohms law lesson:
Where E=volts dc (Vdc), I=current in Amps (A), and R=resistance in ohms
E=I*R
I=E/R
R=E/I
Since power is a function of work we can say that Power (W) in watts is: E*I since in simplified terms both E and I represent work and R is the resistance to work.
Therefore:
In a rheostat calculation:
Fan current draw= 0.1A (substitute your fan current but 0.1 is common)
Voltage is 12Vdc
From this we can assume that a 0.1A fan rates about 120 ohms in actual resistance: 12/0.1=120
Since fan motor resistance is relatively constant we can assume the following:
12Vdc/R1(fan resistance)+R2 (rheostat resistance)=I
Thence: I*E=P
So: A fan rated at 0.1A with a rheostat set to 0 ohms with a 12Vdc supply will run as stated. If the rheostat is set to 25 ohms then we have: 25(R1)+120(R2)=(145t) 12(Vdc)/145t)=.08.
.08*12=.96W. By ohms law we see a voltage drop of 2.0Vdc across the rheostat and the remaining 10.0 across the fan.
If the rheostat is increased to 50 ohms:
50+120=170ohms 12/170=.07A .07*12=.84W Voltage drop across the rheostat: 3.5 across the fan: the remaining 8.5Vdc
If the rheostat is increased to 100 ohms:
100+120=220ohms 12/220=.05A .05*12=.6W Voltage drop across the rheostat = 5Vdc with the remaining 7Vdc dropping across the fan motor.
Of course your fan motor may draw more or less current, but it is simple to substitute you actual values into the above equations.
The point is, your fan should run fine with the Jameco 5watt 100 ohm rheostat mentioned above by Empireking01.
<EDIT> I didn't check the math, I was doing it on the fly so if I missed something, just hollar.
Where E=volts dc (Vdc), I=current in Amps (A), and R=resistance in ohms
E=I*R
I=E/R
R=E/I
Since power is a function of work we can say that Power (W) in watts is: E*I since in simplified terms both E and I represent work and R is the resistance to work.
Therefore:
In a rheostat calculation:
Fan current draw= 0.1A (substitute your fan current but 0.1 is common)
Voltage is 12Vdc
From this we can assume that a 0.1A fan rates about 120 ohms in actual resistance: 12/0.1=120
Since fan motor resistance is relatively constant we can assume the following:
12Vdc/R1(fan resistance)+R2 (rheostat resistance)=I
Thence: I*E=P
So: A fan rated at 0.1A with a rheostat set to 0 ohms with a 12Vdc supply will run as stated. If the rheostat is set to 25 ohms then we have: 25(R1)+120(R2)=(145t) 12(Vdc)/145t)=.08.
.08*12=.96W. By ohms law we see a voltage drop of 2.0Vdc across the rheostat and the remaining 10.0 across the fan.
If the rheostat is increased to 50 ohms:
50+120=170ohms 12/170=.07A .07*12=.84W Voltage drop across the rheostat: 3.5 across the fan: the remaining 8.5Vdc
If the rheostat is increased to 100 ohms:
100+120=220ohms 12/220=.05A .05*12=.6W Voltage drop across the rheostat = 5Vdc with the remaining 7Vdc dropping across the fan motor.
Of course your fan motor may draw more or less current, but it is simple to substitute you actual values into the above equations.
The point is, your fan should run fine with the Jameco 5watt 100 ohm rheostat mentioned above by Empireking01.
<EDIT> I didn't check the math, I was doing it on the fly so if I missed something, just hollar.
- Joined
- Aug 12, 2003
- Location
- West Virginia
Ffats said:
You only actually have to solder two points. If you ground the third point, you won't enjoy the additional heat you'll create
Center point to source, varying resistance output point to fan, wired in series.
HOLY COW PEOPLE!!
All this soldering and "ohms law lessons" business. Lets keep it simple here.
http://heatsinkfactory.com/cgi-bin/HFAstore.pl?user_action=detail&catalogno=CF-030
Its a high cfm 80mm fan....with a speed controller AND a thermal sensor if you want....all for $13.99.
All this soldering and "ohms law lessons" business. Lets keep it simple here.
http://heatsinkfactory.com/cgi-bin/HFAstore.pl?user_action=detail&catalogno=CF-030
Its a high cfm 80mm fan....with a speed controller AND a thermal sensor if you want....all for $13.99.
- Joined
- Dec 13, 2002
- Location
- Southern California
well, you could just try 7volt modding the fan to see if the noise /performance ratio is better for you. connect the 12v from the fan to 12v from the psu, and ground from the fan to 5v from the psu, there are many articles on how tos around here somewhere
- Joined
- Jan 17, 2003
- Location
- Centennial, Colorado
I thought it was "if you give a mouse a cookie"Since87 said:
and isnt the smartfan II thing what I said to begin with? ROFL
- Joined
- Dec 19, 2002
Boy, you people can beat a simple post to death.
The first things is, don't get a rheostat from radio shack they are rated far too low in wattage for a Tornado. You can probably use a 5 watt rheostat and things will be alright as someone posted, but I would get a rheostat equal to the wattage of the fan.
It is also not considered a rheostat if it has 3 connection points, rheostats technically only have 2. It is a Potentiometer
, which you solder the middle connection to one side, making it a rheostat. Your never suppose to leave an open connection on a Potentiometer.
Here is a high wattage Potentiometer that you can use with your Tornado.
http://www.allelectronics.com/cgi-bin/category.cgi?category=470&item=RHE-15&type=store
It works great, its cheap and its safe because of its wattage rating. The RPM's of my Tornado run from around 3300 to full. Keep in mind if you set it too low the Tornado will not start spinning when you power up your computer. It has to be set for at least 3500 rpms to start at power up. Your not gonna find another Potentiometer that will start a Tornado at less then 3500 rpms.
The first things is, don't get a rheostat from radio shack they are rated far too low in wattage for a Tornado. You can probably use a 5 watt rheostat and things will be alright as someone posted, but I would get a rheostat equal to the wattage of the fan.
It is also not considered a rheostat if it has 3 connection points, rheostats technically only have 2. It is a Potentiometer
, which you solder the middle connection to one side, making it a rheostat. Your never suppose to leave an open connection on a Potentiometer.
Here is a high wattage Potentiometer that you can use with your Tornado.
http://www.allelectronics.com/cgi-bin/category.cgi?category=470&item=RHE-15&type=store
It works great, its cheap and its safe because of its wattage rating. The RPM's of my Tornado run from around 3300 to full. Keep in mind if you set it too low the Tornado will not start spinning when you power up your computer. It has to be set for at least 3500 rpms to start at power up. Your not gonna find another Potentiometer that will start a Tornado at less then 3500 rpms.
- Joined
- Dec 19, 2002
Boy, you people can beat a simple post to death.
The first things is, don't get a rheostat from radio shack they are rated far too low in wattage for a Tornado. You can probably use a 5 watt rheostat and things will be alright as someone posted, but I would get a rheostat equal to the wattage of the fan.
It is also not considered a rheostat if it has 3 connection points, rheostats technically only have 2. It is a Potentiometer
, which you solder the middle connection to one side, making it a rheostat. Your never suppose to leave an open connection on a Potentiometer.
Here is a high wattage Potentiometer that you can use with your Tornado.
http://www.allelectronics.com/cgi-bin/category.cgi?category=470&item=RHE-15&type=store
It works great, its cheap and its safe because of its wattage rating. The RPM's of my Tornado run from around 3300 to full. Keep in mind if you set it too low the Tornado will not start spinning when you power up your computer. It has to be set for at least 3500 rpms to start at power up. Your not gonna find another Potentiometer that will start a Tornado at less then 3500 rpms.
The first things is, don't get a rheostat from radio shack they are rated far too low in wattage for a Tornado. You can probably use a 5 watt rheostat and things will be alright as someone posted, but I would get a rheostat equal to the wattage of the fan.
It is also not considered a rheostat if it has 3 connection points, rheostats technically only have 2. It is a Potentiometer
, which you solder the middle connection to one side, making it a rheostat. Your never suppose to leave an open connection on a Potentiometer.
Here is a high wattage Potentiometer that you can use with your Tornado.
http://www.allelectronics.com/cgi-bin/category.cgi?category=470&item=RHE-15&type=store
It works great, its cheap and its safe because of its wattage rating. The RPM's of my Tornado run from around 3300 to full. Keep in mind if you set it too low the Tornado will not start spinning when you power up your computer. It has to be set for at least 3500 rpms to start at power up. Your not gonna find another Potentiometer that will start a Tornado at less then 3500 rpms.
- Joined
- Aug 23, 2003
- Location
- behind the wheel
no one seems to think that his idle is too high? maybe he is simply suffering from lack of airflow inside the case.
even if he has a very good HSF, if his case airflow sucks, he will have high temps.
maybe a better upgrade for him would have been a blowhole and a suckhole(??) for more cool air around the cpu area? They don't add much noise.
edit:
oh crap, sorry for that. just saw that he has a chieftech blue dragon. I had one. Great case.
forget what I said then.
still very high idle. something's not right. what's your ambient temperature?
edit:
actually I just remembered something about the blue dragon. the side blowhole is protected by a mess covering. it might be bad for airflow. try and see if there's an improvement if you replace it with a grill.
even if he has a very good HSF, if his case airflow sucks, he will have high temps.
maybe a better upgrade for him would have been a blowhole and a suckhole(??) for more cool air around the cpu area? They don't add much noise.
edit:
oh crap, sorry for that. just saw that he has a chieftech blue dragon. I had one. Great case.
forget what I said then.
still very high idle. something's not right. what's your ambient temperature?
edit:
actually I just remembered something about the blue dragon. the side blowhole is protected by a mess covering. it might be bad for airflow. try and see if there's an improvement if you replace it with a grill.
Last edited:
- Joined
- Jan 17, 2003
- Location
- Centennial, Colorado
pik4chu said:
OP
- Joined
- Aug 13, 2002
- Thread Starter
- #34
Ambient temp is 73F (prob 22c too lazy to calculate), and my idle temp dropped to 53C with the SK-7 and stock fan in the last 24 hours. Still its higher than the stock heatsink. My airflow in the case should be Ok, I have 1 case fan in the bottom front blowing air in, and one and the middle back blowing out. There is also one on the side window which is blowing air in (my friend told me to make it blowing out, but it made temps higher).
OP
- Joined
- Aug 13, 2002
- Thread Starter
- #35
Hey check this out: http://www.pcmods.com/details.asp?ProdID=4
I think that would work pretty good right?
I think that would work pretty good right?
- Joined
- Aug 8, 2001
- Location
- New Orleans
That idle temp is WAY too high for an SK-7. I'd say there isn't a proper contact. Rub a little grease on the sink, then wipe it off. This way it only fills the microscopic imperfections of the surface. The put a small dab of grease on the CPU core. Install. The whole process is documented at the Arctic Silver website. Use that method.
Something's definately wrong though.
Something's definately wrong though.
If you get higher temps than the stock cooler, you didn't do something right. Take the thermalright off, clean it with soap water, then alcohol. Same with the cpu. Then LAP the thermalright, because they have rough bases. I never put on a new heat sink without lapping it anymore. Then follow the directions dealin' with the thermal goop application. You know, rub the middle of the heatsink base with ceramique or whatever, then rub it off with a coffee filter. Then a mouse poop sized glob of the goop on the cpu. Set the heatsink on, and twist it a bit to cover the services of the core, then screw it on or clip it on. Tada, you should have much better temps.
