MuHcOw,
to OcF !
Trying my best to answer your questions here.
1) IF I where to build my own PWM-controller and (don't know the correct word) power-module??? - Would "PWMing" a 3-pin fan wreck the "fan tach" signal from the third wire?
Yes, PWM-ing 3 wires fan is really crude method to control the fan speed, this simply turning
the whole fan power on and off at very high speed.
Since tach signal is also in pulses (common standard is 2 "pulses" per rotation), definitely this signal will be wrecked so badly that it is useless.
There is other alternative that use this method called pulse skipping, but still this is a really lame method, and also will create even annoying noise from the fan, cause its sort of stopping the pulsing momentarily, then there is a circuit will monitor the tach signal for certain period, and then continue the pulsing again.
This process is repeated again and again that sometimes the fan will create a funny tone.
Simply put, forget about power pulsing PWM on 3 or 2 wires fan, its not worth the effort and troubles.
2) "
Nidec" states that modulating the 12V main supply isn't a good thing to do.
But isn't that exactly what a PWM-fan does? chops up the 12V supply with it's OWN built-in circuitry (with help from an external PWN-controller) in order to control the speed??
Yes, in principal they're "almost" the same, but again, as the olde says "the devil is in the detail"
, as you see, on PWM 4 wires fan, the power is supplied "constantly" to the fan circuit, so the fan circuit is never turned off, also PWM fan circuit is much-much more complicated than ordinary 3 wires fan.
An example, here I made a tear-down of an industrial PWM fan, click ->
Pictures of A Dead Delta Fan and It's Internal Parts, you can see it has complicated circuit with many more tons of components compared to common 3 wires fan.
Now, about the chopping, yes, its using the same principal, but ... it has a dedicated circuit to handle this situation ("smarter") in chopping the power "at the right & precise timing and moment" that this method will be effective. Again, remember, PWM fan has a dedicated circuit and this smart circuit is "constantly" powered on by a dedicated 12 volt line to do this work. 3 wires fan doesn't have this luxury, hence fan with PWM feature will be much more expensive than it's 3 wires brethren or exact same model.
Randomly chopping the power as in pulses to the fan stators definitely will wreck the fan rotation, torque power and reduce the fan efficiency. Combining these disadvantages, usually this method will create annoying weird noise since the pulsating pulse is not fired at the right precise timing and moment.
Made a short explanation here, read it carefully and also recommending to stare at the pic in that post while imagine the overall over process as I explained there, click ->
HERE, trust me, speed it up in your brain, its dizzying.
... LOL ...
The thing is that I have a bunch of 3-wire fans that I would like to run slower. I'm not interested in soldering a resister on one of the wires in order to reduce the speed. Well that would be the easy way to do it, but not a very efficient way.. I'm also worried about the tach-signal..
The only safest & better way to control the speed of 2 or 3 wires fan is by using voltage control (aka reducing voltage supplied to the fan), which is most commercial fan controllers do out there.
Also this old but proven method is the best in controlling and reducing the fan noise effectively.
3) Would using the 556 Dual Timer boost the PWM-signal up to a level where it will damage the circuitry on my 4-wire fans if only ONE fan is connected to the controller?? (yes, I also have a bunch of 4-wire fans)
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Nidec UltraFlo V12E12BS1B5-07 - Very nice (discontinued) fan, I think.
Nope, don't worry, it doesn't work like that. Think of the booster like your PSU, even though it has beefy power, it will only supply the "needed" power which is your fan either single or more safely.
It is like computer with single or multiple hard-disks, you never heard of that a psu was toasting the hardisk if only one was used compared multiple harddisks, right ?
Hope this helps.