- Joined
- Feb 13, 2001
- Location
- Twin Cities
If you are considering implementing a centrifugal blower, such as outlined in my article, http://www.overclockers.com/tips461/index.asp from a few weeks ago, read on. Ditto if you already have.
In my article, I had recommended the Dayton 170cfm DC blower, Model 2C646. Dayton also has a 130cfm AC version of this blower, Model 2C647. If you have not gotten the blower yet, get the AC model. If you have the DC version, don't panic. It works just fine.
I wanted to see how the AC version would work, so I bought just the motor. Upon hooking it up, it performed as well as the DC one, with the exception that it was stuck running at full speed and the vibration was hard to tolerate. Unlike DC motors, you can not regulate the speed of an AC motor as easily as lowering the voltage. They are synchronized to the 60Hz line frequency and that, combined with the number of poles, contributes to the speed.
So, I had written off the Ac motor as a failed experiment and put it on the shelf as a backup. In a post I read last night, it was tossed up whether an AC light dimmer would work. I took this reasoning one step further and picked up a Bathroom Fan speed control, which works on a similar principle. When I got home form work, I wired it in and the results are stunning. You can slow the fan down to almost a complete stall, or run it full tilt. No complex regulator circuits to build, no brush noise (DC version). As I type this, the only way I can tell the blower is running is to look at it and verify the cage is turning. It is quieter than the Northbridge and GPU fans combined with the HDDs. It still gets loud at full tilt mind you, but performs very well at lesser speeds, just like the DC model.
While I'm sure that those of you with the DC version have no desire to throw more money at the project than you already have. You can convert your unit for the cost of an AC motor (appx $20.00) and I got the speed control from Menards for $14.95. You may be able to source both pieces for less through a surplus dealer. I did not try a light dimmer, which cost considerably less than the fan speed control. The controller is rated for 3A of load and has EMI surpression built into it (unlike some cheap light dimmers).
One caveat. If you have read the article, You know that the original design was based upon using one air source to both cool the CPU and provide through-case ventilation. When you turn the AC speed control way far down, it still cools the CPU fine, but doesn't provide sufficient through-case airflow. Normally you would not run it that slow though.
I apologize for not researching this angle more when I was doing the original article. I failed to think far enough "outside the 9 dots". I will continue to work on the last segment of the original article, detailing the variable DC regulator construction.
Hoot
In my article, I had recommended the Dayton 170cfm DC blower, Model 2C646. Dayton also has a 130cfm AC version of this blower, Model 2C647. If you have not gotten the blower yet, get the AC model. If you have the DC version, don't panic. It works just fine.
I wanted to see how the AC version would work, so I bought just the motor. Upon hooking it up, it performed as well as the DC one, with the exception that it was stuck running at full speed and the vibration was hard to tolerate. Unlike DC motors, you can not regulate the speed of an AC motor as easily as lowering the voltage. They are synchronized to the 60Hz line frequency and that, combined with the number of poles, contributes to the speed.
So, I had written off the Ac motor as a failed experiment and put it on the shelf as a backup. In a post I read last night, it was tossed up whether an AC light dimmer would work. I took this reasoning one step further and picked up a Bathroom Fan speed control, which works on a similar principle. When I got home form work, I wired it in and the results are stunning. You can slow the fan down to almost a complete stall, or run it full tilt. No complex regulator circuits to build, no brush noise (DC version). As I type this, the only way I can tell the blower is running is to look at it and verify the cage is turning. It is quieter than the Northbridge and GPU fans combined with the HDDs. It still gets loud at full tilt mind you, but performs very well at lesser speeds, just like the DC model.
While I'm sure that those of you with the DC version have no desire to throw more money at the project than you already have. You can convert your unit for the cost of an AC motor (appx $20.00) and I got the speed control from Menards for $14.95. You may be able to source both pieces for less through a surplus dealer. I did not try a light dimmer, which cost considerably less than the fan speed control. The controller is rated for 3A of load and has EMI surpression built into it (unlike some cheap light dimmers).
One caveat. If you have read the article, You know that the original design was based upon using one air source to both cool the CPU and provide through-case ventilation. When you turn the AC speed control way far down, it still cools the CPU fine, but doesn't provide sufficient through-case airflow. Normally you would not run it that slow though.
I apologize for not researching this angle more when I was doing the original article. I failed to think far enough "outside the 9 dots". I will continue to work on the last segment of the original article, detailing the variable DC regulator construction.
Hoot
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