Temperature Controlled computer Fan - Electronic Circuits Projects Diagrams Free

Setheroo · 5th November 2009, 09:26 PM

Hi there I am wanting to build I believe a fairly simple circuit. I want to put a probe in my computer that turns on a fan when it senses 40 degrees C and turns off when the temp drops below 40 C. Simple on or off I don't want it to be variable speed or anything.

I have some temperature probes from a temp display panel for my computer. The simple probes give temp info by resistance (obviously).

Temp probe give a resistance of about 10k at room temp
I want the circuit to turn on when it has a resistance of about 5.7K
I would also like to have a pot to adjust this voltage as well

I believe the 12 volt fan can draw about .5 amps, but probably best to assume .75 amps to be safe. If its easier I can just use a relay to handle the higher current.

I just started messing with Tiny CAD and I have attached what I have thus far, its not much..

I believe I could use a transistor to do this, but I have no idea on how to do the calculations for anything. Any help is much appreciated!
thank you very much,

Seth

Setheroo · 5th November 2009, 10:50 PM

After much research I was able to find this diagram:

Thermo-Fan to keep your amplifier cool

I think I could just do this instead. The part of it that I am unsure about it the zener regulator. Does it need to be 10v or does it matter?

Seth

mneary · 7th November 2009, 08:41 AM

[edit] His notes are helpful:

"If you just happen to have a regulated 12V supply handy, leave out the 10V zener diode, use a short circuit for R5, and just use the circuit as is."[/edit]

ke5frf · 7th November 2009, 10:11 AM

KISS,
temperature switch, thermostat.

Andrew Leigh · 7th November 2009, 10:33 AM

Hi

If you want to build that circuit here is the PCB layout in Eagle 5.6.0. it is zipped.

I use this circuit and have so for three years, it is excellent.

Cheers
Andrew

Setheroo · 7th November 2009, 02:29 PM

thanks Andrew, the circuit looks great. What kind of set-up do you use for the diodes and what type of diodes do you use?

Thank you,
Seth

Andrew Leigh · 7th November 2009, 04:36 PM

Hi

I happened to have two Gl 9242 laying about so used them. One broke and ended up with one GL9242 and one 1N4141. I have noticed that the circuit does not like two or one for that matter 1N4141.

Dont forget R8 needs calculating according to the article.

I use the fan for a completely different application, it is set to come on at ~28°C and is at full speed at ~35°C. This is nice as it is very quiet at the lower temperatures.

Cheers
Andrew

rohaila · 7th November 2009, 06:41 PM

dear i want some ideas of circuit projects?
plz give me some ideas also give me circuits diagram.

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5th November 2009, 09:26 PM	#1
Setheroo	Temperature Controlled computer Fan Hi there I am wanting to build I believe a fairly simple circuit. I want to put a probe in my computer that turns on a fan when it senses 40 degrees C and turns off when the temp drops below 40 C. Simple on or off I don't want it to be variable speed or anything. I have some temperature probes from a temp display panel for my computer. The simple probes give temp info by resistance (obviously). Temp probe give a resistance of about 10k at room temp I want the circuit to turn on when it has a resistance of about 5.7K I would also like to have a pot to adjust this voltage as well I believe the 12 volt fan can draw about .5 amps, but probably best to assume .75 amps to be safe. If its easier I can just use a relay to handle the higher current. I just started messing with Tiny CAD and I have attached what I have thus far, its not much.. I believe I could use a transistor to do this, but I have no idea on how to do the calculations for anything. Any help is much appreciated! thank you very much, Seth Attached Thumbnails

5th November 2009, 10:50 PM	#2
Setheroo	After much research I was able to find this diagram: Thermo-Fan to keep your amplifier cool I think I could just do this instead. The part of it that I am unsure about it the zener regulator. Does it need to be 10v or does it matter? Seth

7th November 2009, 08:41 AM	#3
mneary	[edit] His notes are helpful: "If you just happen to have a regulated 12V supply handy, leave out the 10V zener diode, use a short circuit for R5, and just use the circuit as is."[/edit] __________________ de KI6RWX Last edited by mneary; 7th November 2009 at 08:46 AM.

7th November 2009, 10:11 AM	#4
ke5frf	KISS, temperature switch, thermostat.

7th November 2009, 02:29 PM	#6
Setheroo	thanks Andrew, the circuit looks great. What kind of set-up do you use for the diodes and what type of diodes do you use? Thank you, Seth

7th November 2009, 04:36 PM	#7
Andrew Leigh	Hi I happened to have two Gl 9242 laying about so used them. One broke and ended up with one GL9242 and one 1N4141. I have noticed that the circuit does not like two or one for that matter 1N4141. Dont forget R8 needs calculating according to the article. I use the fan for a completely different application, it is set to come on at ~28°C and is at full speed at ~35°C. This is nice as it is very quiet at the lower temperatures. Cheers Andrew

7th November 2009, 06:41 PM	#8
rohaila	dear i want some ideas of circuit projects? plz give me some ideas also give me circuits diagram.