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Discussion Starter #1
Has anyone ever used the various high power counter-rotating fans assemblies that Delta or SanAce make?

I'm interested in the SanAce 9CR1212P0G03 because it has a low power mode (that still produces 51 dBA) at a PWM duty cycle of 0. I'm guessing this means there are no PWM signals being driven to the PWM pins on the two separate fan assemblies? So the PWM pins are basically open and floating? Or tied to ground?
 

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Quote:
Originally Posted by 8051 View Post

Has anyone ever used the various high power counter-rotating fans assemblies that Delta or SanAce make?

I'm interested in the SanAce 9CR1212P0G03 because it has a low power mode (that still produces 51 dBA) at a PWM duty cycle of 0. I'm guessing this means there are no PWM signals being driven to the PWM pins on the two separate fan assemblies? So the PWM pins are basically open and floating? Or tied to ground?
Will I'm not an expert on PWM I know that no signal runs fan at 100% . The PWM pulse signal is reverse of fan speed. I know, all PWM fan curves or charts show PWM form 0% to 100% with 100% being the fastest RPM. But reality is the faster / more constant the PWM pulse signal is the less time there is 12v power to fan, which means fan runs.

No PWM signal to 4th pin (PWM pin) results in fan running at full speed.
 

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Discussion Starter #4
Quote:
Originally Posted by doyll View Post

Will I'm not an expert on PWM I know that no signal runs fan at 100% . The PWM pulse signal is reverse of fan speed. I know, all PWM fan curves or charts show PWM form 0% to 100% with 100% being the fastest RPM. But reality is the faster / more constant the PWM pulse signal is the less time there is 12v power to fan, which means fan runs.

No PWM signal to 4th pin (PWM pin) results in fan running at full speed.
If you look at the datasheet for the fan it says a 100% PWM duty cycle results in the highest RPM and a 0% PWM duty cycle results in the lowest RPM.

100% is flat DC and 0% looks to be no signal whatsoever, at least according to wikipedia.

In this particular fan pack assy., it seems like each fan can be controlled independently, but I'm only interested in the lowest absolute RPM possible.
 

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Quote:
Originally Posted by 8051 View Post

If you look at the datasheet for the fan it says a 100% PWM duty cycle results in the highest RPM and a 0% PWM duty cycle results in the lowest RPM.

100% is flat DC and 0% looks to be no signal whatsoever, at least according to wikipedia.

In this particular fan pack assy., it seems like each fan can be controlled independently, but I'm only interested in the lowest absolute RPM possible.
No signal (0% duty cycle) is constant PWM signal .. no current with no pulse.
Full signal (100% duty cycle) is no PWM signa .. constant current with no pulse.
PWM duty cycle and PWM signal in % are the opposite of each other. The higher the duty cycle is in percentage the lower the signal pulse is.

You can prove this for yourself by un-plugging the PWM pin (pin-4) on a PWM fan. When it is unplugged on a functioning PWM fan header the fan will run on constant 12 volt.
 

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Discussion Starter #6
Quote:
Originally Posted by doyll View Post

No signal (0% duty cycle) is constant PWM signal .. no current with no pulse.
Full signal (100% duty cycle) is no PWM signa .. constant current with no pulse.
PWM duty cycle and PWM signal in % are the opposite of each other. The higher the duty cycle is in percentage the lower the signal pulse is.

You can prove this for yourself by un-plugging the PWM pin (pin-4) on a PWM fan. When it is unplugged on a functioning PWM fan header the fan will run on constant 12 volt.
If you have no current you have no signal period.

I had thought duty cycle was a ratio of on time to off time.

If you look at the datasheet for this particular fan it implies just the opposite because it's saying that 0% duty cycle has the lowest RPM and 100% duty cycle has the fastest.
 

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Originally Posted by 8051 View Post

If you have no current you have no signal period.

I had thought duty cycle was a ratio of on time to off time.

If you look at the datasheet for this particular fan it implies just the opposite because it's saying that 0% duty cycle has the lowest RPM and 100% duty cycle has the fastest.
The less time the signal has power the more time the fan motor has 12v power. When signal has power on the mother does not have power.

That is why a PWM fan with 12 volt power on pin 2 and no signal on pin 4 runs on 12v 100% of the time . runs at full speed.
If fan has PWM control and PWM signal is on 100% of the time the fan has no 12v power and does not run.

100% PWM duty cycle is when there is PWM signal.
0% PWM duty cycle is when there is constant PWM signal.

Every time there is a PWM pulse signal the fan motor receives no 12v power.
 

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Discussion Starter #8
Quote:
Originally Posted by doyll View Post

The less time the signal has power the more time the fan motor has 12v power. When signal has power on the mother does not have power.

That is why a PWM fan with 12 volt power on pin 2 and no signal on pin 4 runs on 12v 100% of the time . runs at full speed.
If fan has PWM control and PWM signal is on 100% of the time the fan has no 12v power and does not run.

100% PWM duty cycle is when there is PWM signal.
0% PWM duty cycle is when there is constant PWM signal.

Every time there is a PWM pulse signal the fan motor receives no 12v power.
Did you even bother to look at the datasheet for the fan in question? Because as far as this SanAce fan operates you're dead wrong.
 

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Quote:
Originally Posted by 8051 View Post

Did you even bother to look at the datasheet for the fan in question? Because as far as this SanAce fan operates you're dead wrong.
I don't care what the fan's data sheet says. I'm telling you what PWM signal is, not PWM duty cycle. Most people do not know there is a difference.

I think you are confusing "PWM duty cycle" with "PWM signal cycle". "PWM duty cycle" is the exact opposite of what "PWM signal cycle" is. They are only the same at 50%

If a PWM fan is receiving 100% duty cycle PWM signal there is an open PWM circuit the PWM circuitry in fan sends constant 12v power to fan motor.

If the is a 0% duty cycle PWM signal (and fan does not have a low speed limit) the fan is receiving a constant PWM signal and the PWM circuit in the fan sends no 12v power to fan motor.
0% PWM duty cycle = 100% PWM signal cycle = 0% power to fan
10% PWM duty cycle = 90% PWM signal cycle = 10% power to fan
20% PWM duty cycle = 80% PWM signal cycle = 20% power to fan
30% PWM duty cycle = 70% PWM signal cycle = 30% power to fan
40% PWM duty cycle = 60% PWM signal cycle = 40% power to fan
50% PWM duty cycle = 50% PWM signal cycle = 50% power to fan
60% PWM duty cycle = 40% PWM signal cycle = 60% power to fan
70% PWM duty cycle = 30% PWM signal cycle = 70% power to fan
80% PWM duty cycle = 20% PWM signal cycle = 80% power to fan
90% PWM duty cycle = 10% PWM signal cycle = 90% power to fan
100% PWM duty cycle = 0% PWM signal cycle = 100% power to fan
 

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Discussion Starter #10
Quote:
Originally Posted by doyll View Post

I don't care what the fan's data sheet says. I'm telling you what PWM signal is, not PWM duty cycle. Most people do not know there is a difference.

I think you are confusing "PWM duty cycle" with "PWM signal cycle". "PWM duty cycle" is the exact opposite of what "PWM signal cycle" is. They are only the same at 50%

If a PWM fan is receiving 100% duty cycle PWM signal there is an open PWM circuit the PWM circuitry in fan sends constant 12v power to fan motor.

If the is a 0% duty cycle PWM signal (and fan does not have a low speed limit) the fan is receiving a constant PWM signal and the PWM circuit in the fan sends no 12v power to fan motor.
0% PWM duty cycle = 100% PWM signal cycle = 0% power to fan
10% PWM duty cycle = 90% PWM signal cycle = 10% power to fan
20% PWM duty cycle = 80% PWM signal cycle = 20% power to fan
30% PWM duty cycle = 70% PWM signal cycle = 30% power to fan
40% PWM duty cycle = 60% PWM signal cycle = 40% power to fan
50% PWM duty cycle = 50% PWM signal cycle = 50% power to fan
60% PWM duty cycle = 40% PWM signal cycle = 60% power to fan
70% PWM duty cycle = 30% PWM signal cycle = 70% power to fan
80% PWM duty cycle = 20% PWM signal cycle = 80% power to fan
90% PWM duty cycle = 10% PWM signal cycle = 90% power to fan
100% PWM duty cycle = 0% PWM signal cycle = 100% power to fan
But this fan's datasheet turns that theory completely on its head. Because @ 100% duty cycle it's at it's fastest RPM, not it's slowest.

So the datasheet must be wrong? From SanAce?
 

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Quote:
Originally Posted by 8051 View Post

But this fan's datasheet turns that theory completely on its head. Because @ 100% duty cycle it's at it's fastest RPM, not it's slowest.

So the datasheet must be wrong? From SanAce?
STOP!
Look very carefully at the relationship between DUTY CYCLE and PWM CYCLE in the my post you just quoted.

PWM DUTY CYCLE is not the same thing as PWM SIGNAL CYCLE.

100% duty cycle is 0% PWM pulse signal is 100% 12 volt power to fan!

I know what I'm saying even if you can't read and understand it.

The whole reason for 10 lines of duty cycle, PWM signal cycle and fan motor speed what to show you in extremely simply terms how it all works. If you can't figure it out, tought! I'm done trying to explain it.
 

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Discussion Starter #12
Quote:
Originally Posted by doyll View Post

STOP!
Look very carefully at the relationship between DUTY CYCLE and PWM CYCLE in the my post you just quoted.

PWM DUTY CYCLE is not the same thing as PWM SIGNAL CYCLE.

100% duty cycle is 0% PWM pulse signal is 100% 12 volt power to fan!

I know what I'm saying even if you can't read and understand it.

The whole reason for 10 lines of duty cycle, PWM signal cycle and fan motor speed what to show you in extremely simply terms how it all works. If you can't figure it out, tought! I'm done trying to explain it.
From the data sheet for the fan in question:

PWM Duty Cycle(%) Rated Current (A) rated speed (RPM)
0% 1.1 2,700 1,800
100% 7.2 6,200 3,800

It makes sense but 0% duty cycle should be no power to the fan, but it's NOT.
 

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Quote:
Originally Posted by 8051 View Post

From the data sheet for the fan in question:

PWM Duty Cycle(%) Rated Current (A) rated speed (RPM)
0% 1.1 2,700 1,800
100% 7.2 6,200 3,800

It makes sense but 0% duty cycle should be no power to the fan, but it's NOT.
Yes, 0% duty cycle is no power to fan motor ..that it is 100% PWM signal to PWM circuit in fan housing and fan motor has no power.

If 0% PWM duty cycle was 0% PWM signal, PWM fans would only run when connected to functioning PWM headers.

If it worked the way you were thinking and we plugged a PWM fan into 3-pin variable voltage fan header PWM fans would never run .. because their internal PMW circuitry would not supply power from pin-2 power on fan header to fan motor.

But we know they do run on variable voltage headers,
therefor we know that with 100% PWM duty cycle on pin-4 the PWM fan's PWM circuitry is receiving 0% PMW signal and fan runs at 100% speed.
wink.gif

Which is what I kept beating you the way I did.
0% PWM duty cycle = 100% PWM signal cycle = 0% power to fan
10% PWM duty cycle = 90% PWM signal cycle = 10% power to fan
20% PWM duty cycle = 80% PWM signal cycle = 20% power to fan
30% PWM duty cycle = 70% PWM signal cycle = 30% power to fan
40% PWM duty cycle = 60% PWM signal cycle = 40% power to fan
50% PWM duty cycle = 50% PWM signal cycle = 50% power to fan
60% PWM duty cycle = 40% PWM signal cycle = 60% power to fan
70% PWM duty cycle = 30% PWM signal cycle = 70% power to fan
80% PWM duty cycle = 20% PWM signal cycle = 80% power to fan
90% PWM duty cycle = 10% PWM signal cycle = 90% power to fan
100% PWM duty cycle = 0% PWM signal cycle = 100% power to fan
 

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Discussion Starter #14
So this particular model of SanAce fan doesn't comply w/the standard for all other PWM fans?

I read a Delta datasheet that had it more plainly presented (in the way you did, but they had RPM's for the fan too at various PWM duty cycles).

Thanks Doyll.

For this fan does it need TWO PWM headers to function? It looks like there's two sets of 4-lines going to each fan in the assy.

Does PWM give you finer control over RPM's than voltage controlled fans?
 
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