So two months ago, I went to shopping for better cooler, finally I decide to buy the ZALMAN CNPS8700LED full copper cooler. In fact, it left me no any other choice at All IT Hyper Market there, most cooler sell there is gigantic which definitely can not be installed into a low profile system. In fact, I can only say that this is the only option I can get there for my system. And so I quickly grab (grab? OK, purchase one) one.
With the CNPS8700LED full copper cooler, I am happy and go home to test it out. Unfortunately, after unpack the cooler then only I notice that the cooler fan is an old fashioned 3-pin fan without PWM fan speed controlling pin. This is a little bit annoying because it simply mean that the AMD Cool'n Quiet won't be quiet actually. Although at the box there, it written "ultra quiet" cooler, but the fact is the fan provided isn't really so quite at it full speed which I plug in the 3-pin fan directly onto the motherboard with 4 -pin socket.
To address this issue, ZALMAN fan actually come with a simple fan controller Fan Mate 2 which allow us to manually adjust the speed of the fan at a balance of performance and noisy level preferred.
But I just don't like it, who wanna frequently control the fan them-self I want an automatic Cool'n Quiet but not Hot'n Quiet. The fan should be allowed to run at higher speed when the CPU is getting hotter!
Therefore I begin to spend some time to develop my own "4-Pin to 3-Pin CPU Fan connector", it is just a piece of cake which can be done in one day by just using some electronic spare part on my desk. Adding some delay circuit with potential-meter will delay the speed of PWM fire, therefore lowering the minimum RPM of the fan. The delay time will gradually reduces when the PWM pulse width increased, because less "off" time to charge up the capacitor use for storing charge for delay.
Now, the motherboard can freely adjust the fan speed itself, from 800RPM to 2150RPM itself according to the temperature and potential-meter position. At potential-meter fully clockwise, it will rotate at the range 800RPM to 2150RPM, at fully counter close wise it will rotate at the range of 1700RPM to 2150RPM for my ZALMAN fan. Somehow, the speed controlling is not linearly act accordingly to temperature, but overall it give me satisfaction.
I have been using it for more than one month now and it seem still functioning well.Now my CPU running only about 44-48 degree Celsius at idle and a merely 56 to 62 degree Celsius at full loading for 1-2 hours.
Update: 07thJuly09
The schematic below is the circuit described use, it may not be the best, but it have serve me nearly half years now. I do not guarantee it will work, make it at your own risk.
The 470nF capacitor will delay the PWM for fire (turn on, in power electronic, like driving a SCR, we like to use the word fire, it is cool!), if C1 is too large in capacity, PWM will never off, the fan will gain peak voltage continuously. The inductor is an optional component, I use a 100uH one, it will provide more stable output, do not use a capacitor to smooth out the output, it will overheated, since the circuit is not calculated for a true buck regulator.
The 470nF capacitor will delay the PWM for fire (turn on, in power electronic, like driving a SCR, we like to use the word fire, it is cool!), if C1 is too large in capacity, PWM will never off, the fan will gain peak voltage continuously. The inductor is an optional component, I use a 100uH one, it will provide more stable output, do not use a capacitor to smooth out the output, it will overheated, since the circuit is not calculated for a true buck regulator.
The UC3843 conveniently provide 5V for TTL logic interface, which eliminate the need for fixed voltage regulator like 7805, it is a very common low cost PWM ic, it also reduce the number of transistor use, so overall use of UC3843 is cost effective because I have purchase them in bulk! May be not all (from different manufacturer) UC3843 can use in this way, because it is not designed for such usage.
I know this is not a very good circuit, but overall it work just fine.
*L1 shoud be 100uH, 2N2907 is draw upside down!(collector and emitter is reversed!), sorry for that, please take caution.
If you have any inquiry regarding this article, please feel free to email me at mail.altbattery@gmail.com. Remember to put a title name: "To David, About PWM Fan."
Ok, thanks for reading, and if you have time, please take a look at the link: video games waste energy and contribute to global warming
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