temp cantrolled fan circuit

[Matttcattt]

will any/all of the following 3 circuits work? will my circuit (attached) also work? do i need to add anything, can i remove anything? do i need feedback? one of the 10k resistors in the right hand potential divider will be a verial resitor to set temp. also, the values are not correct, i will have to play around. thank you for any help in advance.

http://www.uoguelph.ca/~antoon/circ/heatsens.html

http://www.rason.org/Projects/fancont/fancont.htm

http://www.overclockers.com.au/techstuff/a_thermalfans/

thanks again

 

[jackinnj]

There a single chipsolutions

Analog has a couple in which only one resistor is used for the "setpoint" -- I believe that they cost in the vicinity of $2.00 I would expect all the usual suspects (Int'l Rectifier, TI, National, Maxim) to provide something similar.

 

[Matttcattt]

what do these chips do? do they output PWM or the fan voltage? if PWM, i just want to use a 741 opamp, a thermister and a 2n3055. i already have these.

 

[Matttcattt]

i was thinking that there are three ways to do this:
a potential divider connected to a transistor's base
the circuits above
a thermister used in a 555 timer circuit, used as a PWM pulse contolling motor speed

which would be best? i have made a working prototype of my circuit above.

 

[Bricolo]

I haven't found easier

An externally hosted image should be here but it was not working when we last tested it.

 

[Matttcattt]

cool, thanks a lot. where can i get the LM317? and can i get free samples from anywhere? thanks again.

 

[Andypairo]

I don't think that a old 50 cents part can still be in a sample program.... when parts are dirty cheap and can be found even in a grocery (or almost...) I see no point in looking for free samples.

Cheers

Andrea

 

[Matttcattt]

could i use a different voltage regulator, and play with the values, or does it have to be a LM317?

 

[s0rce]

My dad put this together a few years back, I hope it help.

An externally hosted image should be here but it was not working when we last tested it.

 

[JOE DIRT®]

Matt....your a cheapo..LOL....with the parts you have you can build a temp. unit...there are a alot of design examples out there using an op amp as a comparator....if you really want it for free go to Maxim`s site and look at the Dallas temp controllers I`m utilising one right now with a PIC

DIRT®

 

[Matttcattt]

all those ICs need more than 3 components

i smallest value thermister i can get is 4k7, the circuit states 470R. would the fixed resistor go up or down in value? up i guessing. what value would you suggest? im going to use a multi-turn preset to adjust temperature.

 

[Matttcattt]

any help?

 

[Matttcattt]

any help?