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ntc thermistor for auto rpm pc fans Answered

i have 470 ohm thermistors and i want to auto control my pc fans ie when the temperature is low the fans are off or low speed,when temperature go high the fans rpm follow up.
is there a scematic how to do a pcb?


after several trials i get that.
i don't try it a lot to figure out it's functionality.I know isn't the perfect circuit,but if anyone wants try out and improve that!!!
sorry for the scematic,i made it in photoshop!!!!!! lol

NtcThermistorSmart fan.jpg

   Clever circuit.  Are you using the thermistor to control the voltage to the fan? Does it work?

If what you have for a fan is a brushless motor, generally you can't control it by decreasing the current.  The motor may slow down and eventually stall, but it will heat up and may be damaged.  Search for instructables on   controlling motor speed.

Anyway, good luck.

i used an LM317T,a 470 ohm Thermistor and a 100nF (i don't know its name in English)

I am no expert on motors, but I don't think controlling a computer fan with a thermistor is an easy project.<br /><br />From what I can find out, computer fans utilize brushless motors to minimize electrical and magnet interference: "BLDC (brushless dc) motors have come to dominate many applications: Consumer devices such as computer hard drives, CD/DVD players, and PC cooling fans use BLDC motors exclusively." This is from http://en.wikipedia.org/wiki/Brushless_DC_electric_motor<br /><br />The BLDC motor is controlled by timed pulses. It is not hard to generate timed pulses with a 555 timer, and the 555 timer pulse frequency can be changed with a variable resistor, which is what a thermistor is. However, getting the right frequency would take experimentation. The pulses would have to be amplified, but this can be done with an NPN transistor.<br /><br />You may be able to get more useful information from http://aquaticus.info/bldc_controller The designer invites queries at <div>rov@aquaticus.info.<br /> </div> Hope this helps.

This should give you a start on your project.  The exact values of parts are determined by the part you have.

Did you look at the data sheet that came with your thermistor?

first sorry for my english(i am greek)
second i dont have a data sheet,my mother bring me the thermistors because i live in an island and here i cant find any.

What are the numbers on the parts?<br />You can download data sheets from the internet.<br />The data sheets usually have suggested circuits on them.<br /><br /><a href="http://www.google.com/search?q=datasheets&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a">Data sheet links.</a><br /><br />Good luck.<br /><br />

i didnt find anything yet but i continue looking.
thanks for the help.