PC Fan wiring

[Osprey]

Going to be using a PC fan on a non-PC project.

 

I bought the ARCTIC F12 PRO TC

 

It arrived ... and as well as standard 3 pin lead which is normally +ve, -ve & tacho

It has a separate lead with temp sensor ..... I do not wish the fan to control itself I want to control it from external unit .... anybody know how to disable this temperature sense function.

[KenB]

Hi

 

I have to ask - why buy this one if you didn't want the temperature function ?

 

From what I can find out ...

The fan will rotate at approx 400 r/m if the sensor is in a cool location.

This will increase to about 1,300 r/m if the temp is 40 C or above.

 

The sensor will be a thermistor. This is basically a resistor that changes its resistance with temperature.

As the temperature rises - the resistance decreases ( for most thermistors ...i.e. negative temperature co-efficient )

There will be another resistor in series with this. The mid-point between the two resistors returns a voltage. As the voltage here changes this is what controls the fan.

[ At least this is how I see it working ]

 

If you cut the sensor off you will get one of the two extremes ( either 400 r/m or 1300 r/m )

Obviously with the sensor gone this will fix the fan speed.

 

If this isn't the speed that you want you can try various resistors across the two wires that were attached to the sensor.

You could also try a pre-set resistor ( small variable ) using the centre connection and one of the others.

This would be trial and error for values as we do not know the resistance extremes of the sensor.

 

I want to control it from external unit .

Is the fan just to have an on / off function or are you intending to control the speed from this unit too ?

 

Hope this helps.

[Osprey]

It did not say it had temperature function .... I had just 'searched' for Arctic F12 on the advice they were quiet fans & come with isolation mounts.

 

This is being used to fit in a comms cupboard ... and will be fully temperature controlled by a PWM temperature operated speed controller, with it's own thermistor controlled speed. The reason for this is that I want fan to be OFF when below threshold temp, not running slow.

 

Hence only need 2 leads needed + & - the tacho can be simply ignored.

I have tried ARTIC support but cannot get any reply.

 

If necessary I will have to buy another fan ... just a bit of a waste.

[KenB]

By what I can find out - this fan seems to be running all of the time.

Not what you want ....obviously.

 

Sorry I cannot be of further help. :(

[Plastic Nev]

Hi, firstly what happens if you just connect a + and - voltage to just those leads?

The extra leads coming out, I have just watched this Youtube video of a guy unpacking one. The sensor is on the end of a short twin cable.

 

 

It may need nothing more than the sensor disconnecting and the two wires connecting together, the fan would likely run at full speed or very slowly, if very slowly what happens if the wires are not connected together?

Final speed then is determined of course by the external controller.

 

Nev.

[Osprey]

I have bet the bullet and ordered another ... This time Arctic F12 (non TC) only £3 incl delivery

 

I can always stick the temp control ver in my POC case ... it's got room for another 2 fans

[KenB]

Let us know how you get on with the comms cupboard :)

[Osprey]

will do ...

if anyone is interested there is a simple and cheap cct to give what I wanted ... fans totally off when below threshold temp .... and then they kick-in, ramping up until temp starts dropping back.

cct & details can be found here - http://www.bit-tech.net/modding/2001/12/03/pwm_fan_controller/1

 

No pcb needed, all fits on a very small piece of verboard.

 

lots of discussion on design here: http://forums.bit-tech.net/showthread.php?t=2298

 

All parts readily available ... very cheap as all the PWM control is all on board the single device ...Micrel device MIC502

http://www.micrel.com/index.php/products/power-management-ics/system-management/fan-control/article/1-mic502.html

[KenB]

That is a very nice IC [ MIC 502 ]

It looks like a combination of an OpAmp and a 555 Timer.

 

We used to use 555s with kids in school on projects to control motor speeds using a variable resistor - This was manual.

[ That takes me back a few years :) ]

[Osprey]

I started off with Veroboard & discrete components .. surprising what you can build with a couple of transistors and a sprinkling of caps & resistors.

I had 2 years running for Xmas the "Phillips Junior Electronic Sets" I and II

Noticed set one sold for £50 on eBay http://www.ebay.co.uk/itm/VINTAGE-PHILIPS-EE-1050-COMPACT-ELECTRONIC-ENGINEER-KIT-1970-039-s-photos-/310624505366

and that was an incomplete set ... maybe I ought to sell my 2 mint sets.

 

It was an achievement building your own radio set :)

Moved on to using 741 op amps 555 timers and 74 series logic chips.

It was a couple of decades before I built my first PC ...

[Plastic Nev]

Hi, looking at that circuit and the final switching power transistor,TIP122 when in use with the fan running check it for getting warm, it does depend on the fan size as he said up to 60 watts it should be OK anyway.

However to save a few pennies, I once used a piece of copper as a heat sink, just to help a power transistor keep cool. A short 25mm length of 15mm copper water pipe, slit lengthways, then unrolled to a flat and bolted to the mounting hole, surprising how much heat that gets rid of. If you use the layout he suggests, first flatten the copper to a flat sheet, then bend it to a |_| shape to surround the transistor.

[Osprey]

Fans are only 2.4W each so doubt it will get warm. I will check it though.

[KenB]

I started off with Veroboard & discrete components

Yep - me too. That was about 25+ years ago.

I still had veroboard in my stock cupboard when I left :)

[Osprey]

I used to have Practical Electronics & Electronics Today International ..( ETI )

and built many projects .. amps, tuners, car electronics etc.

Then in mid 80's they started building overly complex projects ... microprocessor, eproms, phase locked loops to make a car indicator flasher ..

That sort of thing.

So stopped making ccts at that time.

Have a whole load of components if I could someone to donate them to.

 

Occasionally make something to do a small job .. such as this one.

[KenB]

started building overly complex projects ... microprocessor, eproms,

Electronics started changing direction in the latter years that I was working.

The exam boards started pushing PIC based projects ( Peripheral Integrated Circuits ) programmable ICs.

I enjoyed this side of it as it integrated programming with Electronics. It took a lot of the understanding of basic electronics away though as PICs could be used to substitute for complete circuits that used to be built with discrete components. Progress :)

 

Have a whole load of components if I could someone to donate them to.

My old school would welcome them - but I suspect that you are too far away to collect :)

Depends on what part of Wales you are ......I know they collect kids from as far away as St. Asaph

[Plastic Nev]

Hi, you just might be interested in this forum I found some time since, a very interesting group and worth a look at.

 

http://www.electro-tech-online.com/

 

Being a licensed radio ham, I also know there are many other electronic and radio amateur websites as well, just google amateur radio, electronics, or any other combination such as vintage radio, you will find a few sites where the old glass bottles (valves) are a part of it.

 

Nev.