I don’t know if this info has been posted before, but here goes.
Several months ago I purchased a Comair Rotron Major 12VDC axial fan, model number JQ12ROX, 235cfm, 171.5mm x 150.4mm x 50.8mm. The cost was right, 14.95USD, so I bought 2 of them from MPJA. Well I finally decided to see how to use all of its features. This is a discontinued model (mfg OCT 2000 I think). Comair does not have info on their web site for this model.
It has 4 leads coming out to a nice 5 pin socket::
1 red lead wire (obviously the +12vdc)
2 blank socket pin
3 yellow lead wire (?)
4 blue/white striped lead wire (?)
5 black lead wore (obviously the – return)
My electronics knowledge is very limited. But I do not shy away from the simple things (soldering, measuring resistance, etc). At the Comair site I found some info in their engineering notes:
Their fans have built in electronics for extra functions, but different models have different ways of implementing this.
Speed control:
http://www.comairrotron.com/Engineer...olFanSpeed.htm
The yellow wire is for speed control
I decided to see if the simple implementation was used. I shorted out the yellow lead to the black lead and sure enough the fan speed dropped significantly (low speed). This is great so I found a 10K pot in my collection and placed it between the yellow lead and the black lead. This allowed me to continuously vary the speed from full to half speed. I noticed that the sound no longer changed about half way in the rotation of the pot wiper. So I left it there and measured the resistance at that point. It was close to 5K. No 5K pots in my collection. So I’m off to the local Radio Shack. Where I purchased a 5K ohm 0.5watt linear pot (part number 271-1714). With this between the yellow and black leads I had full speed control over the full range of the pot.
None of the fan controllers, that we see advertised everywhere, can be used even if they could handle the 2.26 amps (27watts) that this fan needs. Changing the voltage on the +12 volt lead (red wire) only gives you 2 speeds (internal electronics on the fan does this). From ~ +6 to +12 gives you the high speed. Below ` +6 volts gives you the low speed. But this cheap little pot on the speed control lead (yellow wire) does the trick.
Performance monitoring.
http://www.comairrotron.com/Engineer...torFanPerf.htm
The blue/white wire is for fan performance monitoring (RPM)
Now to see if the performance lead (blue/white) is the simple 2 pulse per revolution output used by some fans in our computers. I placed one end of a micro clip on the pulse sensor lead on one of the fan sockets of my DigitalDoc 5. The other end of the micro clip was placed on the blue/white lead from the fan. It worked. The DigiDoc showed 3520 RPM at full speed and 1344 RPM at low speed.
Now all I need is a plug for the blue/white lead.
That’s how I tamed my Comair Rotron. If yours has a different model number it may require other solutions.
Next on my list, building a radiator shroud for this fan. At the rate I’m going it may be quite a while. I have made 2 that were complete disasters. Oh well live and learn.