Introduction:

   How many times have you sat next to your computer doing work but couldn't concentrate because the roaring of your 4 80mm Panaflo's?  Or how many times were you just too tired to get out of bed to turn down your fans on your baybus?  Well you have the chance to make an easy to build controller to turn the fans up and down automatically according to temperature.

Here are the parts you'll need.

This is what you'll need:

- a 470 ohm NTC thermistor
- a 40x1 pin header
- 3 pin header connectors (set of 2, metal contacts and plastic holder)
- a 317T adjustable voltage regulator
- a 2.2k ohm resistor 1/4 watt
- a 100 nano-farad capacitor
- a piece of prototyping pcb
- a length of heat shrink tubing
- a length of wiring
- and obviously your soldering iron, solder, flux, etc...

Preparation:

   Break apart your 40x1 pin header so that you get 1 4x1 piece and 3 2x1 pieces, the rest you can save to use in another project or to poke your friend's eyes with.

1 4x1 piece and 3 2x1 pieces.

Getting down to business

  Now here comes the fun part, get your prototyping board and follow the instructions.

Doesn't seem so hard does it?

Step 1: Solder on your 2.2k ohm 1/4 watt resistor like so.

Now there's 2 things on the board, yes!

Step 2: Go five holes down and solder in your 100 nano-farad capacitor.

Its getting a bit more interesting now.

Step 3: Place and solder your pin headers like so.

Almost done, what!? almost done?

Step 4: You 317T adjustable voltage reg. is next.

Here's the hardest step. Left is unconnected - Right is connected.

Step 5: Start joining the components, follow the colour chart above.

Last Step: Now using Stygian's article on constructing the thermal probes make yourself a thermal probe with the 470 ohm NTC thermistor.  Add a connector to your fan in question as well.

This is the completed thermal probe.

And there's the fan with the pin connector.

You're Done! Woo hoo!

   The only thing left now is to connect your contraption up and test it.  I'd recommend that you test it on another power supply that your computer is not using first before you plug it in.  Like all other articles put out on the net I'm warning you ahead of time, so don't blame me if you blow up your power supply.

You really have to be careful here so you don't blow up your computer.

Connecting the beast

   Now I know after you worked on all this you are going to be very eager to plug this thing in and try it out, DON'T!  Please read and make sure you know what is going to go where, and if you're not sure read some more.  This can potentially blow up your power supply if you're not careful.

NEGATIVE TERMINAL	This will be the negative end where you plug your things into.
POSITIVE TERMINAL	This will be the positive end where you plug your things into.
THERMAL PROBE CONNECTOR	This is where your thermal probe plugs into, there is no positive or negative end.  You can plug it in either way.
12 VOLTS	This is where you apply power to the controller.  This will fit the small power connectors used to power floppy drives.  Match the yellow wire on the connector to the last pin where the 12VOLTS is marked.

  Also take notice that there are 2 connectors where you can plug your fans into.  This is intentional so that you can also plug in a LED in series with a resistor of course to show a visual representation of the power your are getting to your fans, perfect for fan-busses.

   Last but not least, experiment with different values of thermistors.  470 ohms will give you almost peak output (12V) at 25 degrees Celsius, try a lower or higher value to adjust to your liking.  There is also another thing to say about this circuit, this is a circuit is low in cost but wastes a bit of power.  Don't expect your fans to ever get a perfect 12V, a figure of about 10-11V is more accurate.  I will be writing a new article sometime in the near future that will show you how to make a more efficient controller capable of giving near 12V output.

   For those of you who want a breakdown of the cost here it is, this is from the local electronics shop that I buy my stuff from.  Prices in your area may differ.  Prices listed below are in Canadian funds.

470 ohm NTC thermistor 40x1 pin header pin header connectors (set of 2, metal contacts and plastic holder) 317T adjustable voltage regulator 2.2k ohm resistor 1/4 watt 100 nano-farad capacitor piece of prototyping pcb length of heat shrink tubing length of wiring

$0.75/each $0.40/each $0.15/each (set of 2) $0.75/each $0.01/each $0.10/each $0.95/each $0.15/foot $0.15/foot

  Hope you enjoyed the article, have fun building it. But BE CAREFUL!

eipromb.