Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Raspberry(3b+)-PCA9685-12V Fans

Sun Aug 26, 2018 6:00 pm

Hello,
i need to drive 4 PWM Fans.
2x Noctua NF-P14s 1200 PWM
2x Noctua NF-A14 industrialppc 3000 PWM

I tested the PCA9685 with a external 12V Power Source.
The Noctua NF-P14s 1200 PWM works fine but the Noctua NF-A14 industrialppc 3000 PWM just runs at 100% every other % is off.

Can somebody help me with that?

Thanks

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Aug 26, 2018 6:10 pm

How did you connect it al to each other? The maximum voltage of the pca is 6v.

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Aug 26, 2018 6:22 pm

Hi,
like this:
Unbenannt.png
Unbenannt.png (173.54 KiB) Viewed 751 times
But i think the Problem is that the most PWM speed controlled computer fans are designed assuming a 25KHz control signal.
The PCA9685 has a maximum frequency of about 1.6KHz. Some fan will work with that. Others do not.

So i have to find an other way to do that but atm i dont know any.

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Aug 26, 2018 6:35 pm

First of all, I see that you fan have's 4 pins to control it. Because, as I remember correcly, with a 4 pin connector one is the pwm input and the other is the "tach" output.

edit
Do you have the datasheet / spec. for the fans that you are using? Maybe they tell something about the correct voltage / frequentie.
Last edited by Brandon92 on Sun Aug 26, 2018 6:39 pm, edited 1 time in total.

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Aug 26, 2018 6:39 pm

Hello,
u are right, these are 4Pin fans.
Unbenannt.png
Unbenannt.png (8.36 KiB) Viewed 738 times
The RPM Speed Signal is not connected cause i dont need it.

Edit:
Noctua itself dont share informations about that but u can find it here:
https://github.com/sbambach/MK2-X2/blob ... M_Spec.pdf

Frequency: 25kHz nominal, 21-28kHz is acceptable
Current sink capability: 5mA required, 8mA recommended
Maximum voltage capability: 5.25V
Maximum VOL: 0.8V

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Aug 26, 2018 6:49 pm

If I take a look at dspecification document you need indeed a frequentie between 21-28kHz.

edit
We found the same document :D
But, I think that is indeed the problem. You need a faster pwm signal.

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Aug 26, 2018 6:56 pm

Yes but on which way i can create one?
Is is possible to connect the PWM directly to the Gipo and use Software pwm or did it damage the board?

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Mon Aug 27, 2018 4:42 pm

Nobody?

User avatar
davidcoton
Posts: 3163
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

Re: Raspberry(3b+)-PCA9685-12V Fans

Mon Aug 27, 2018 4:51 pm

Ch3fk0ch wrote:
Sun Aug 26, 2018 6:56 pm
Is is possible to connect the PWM directly to the Gipo and use Software pwm or did it damage the board?
Compare the specs. The fan needs a 5V tolerant source and up to 8mA current sink.
The Pi GPIOs are 3V3 maximum, and won't happily sink 8mA.
So no, you cannot connect directly, it will damage your Pi. Probably it will completely kill it.

You need a simple NPN transistor buffer. Resistor (10K) form GPIO to transistor base, emitter to ground, collector to fan control.
"Thanks for saving my life." See https://www.raspberrypi.org/forums/viewtopic.php?p=1327656#p1327656
“Raspberry Pi is a trademark of the Raspberry Pi Foundation”

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 12:01 pm

So i testet it like this:
5486cb23c26e1baec36144e0aa6b0194.jpg
5486cb23c26e1baec36144e0aa6b0194.jpg (60.42 KiB) Viewed 608 times
But it dont work.


I hope someone can help me to get this running....

User avatar
davidcoton
Posts: 3163
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 1:46 pm

Ch3fk0ch wrote:But it dont work.
We can't work out why not, and therefore what is wrong, from that.

What bit didn't work?

How did you check and test your circuit?
Could you read the temp sensor?
Did you produce a PWM signal?
Did the fan turn at all?

What program did you use to convert temperature to PWM? (Post it here in [code][/code] tags).
How did you try to debug the program?
"Thanks for saving my life." See https://www.raspberrypi.org/forums/viewtopic.php?p=1327656#p1327656
“Raspberry Pi is a trademark of the Raspberry Pi Foundation”

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 2:32 pm

I just use the the "PWM-Part" from this.
So i connect the BC238 Base over a 1k ohm transitor a Raspberry Gpio, the emitter to ground and the collector to fan control.
The Fan is also connected to a 12V Power Source.

Did you produce a PWM signal?--->>> Yes
Did the fan turn at all?---->>> Yes

But i still cant controll the Fan with PWM.

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 2:45 pm

Did you connect the Rpi ground to the ground of your fan and transistor?

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 2:54 pm

To the emitter of the Transistor and to the Ground of the 12V Powersource.

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 3:08 pm

So, there is no ground connection from the emitter to your Rpi?
There should be one. Because the Rpi delivers a current to the base of the transistor, and that current need to go back to the Rpi. Otherwise the transistor wont turn on.

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 3:10 pm

Sure, there is.

I make a quick scatch.

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 3:20 pm

Ok Here:
BC-238.jpg
BC-238.jpg (79.63 KiB) Viewed 548 times
Just run fullspeed or off.

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 3:30 pm

Okey thanks for the diagram.

You need to add a pull-up resistor between the collector and the 5V rail.
As stated in "PWM control input signal" in the file that you provided.

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 3:35 pm

U Mean something like this?
BC-238.jpg
BC-238.jpg (89.23 KiB) Viewed 534 times

Thanks

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 5:04 pm

Ehm, maybe you don't need a pull up resistor:
Test Methodology
To measure the pull up and current sourced from the fan, power the fan to 13.2V and use a DMM
(Digital Muli-meter).
To verify the pull up value in the fan, measure the voltage between pin 4 (control) and pin 1
(ground).
To verify the current sourced by the fan, measure the current between pin 4 (control) and pin 1
(ground).
1. The trace from PWM output to the fan header must not have a pull up or pull down. The pull
up is located in the fan hub. The presence of a pull up on the motherboard will alter the fan
response to the PWM Duty Cycle. In some cases this may prevent the fan from achieving
full speed even with the Hardware Monitor device issuing a 100% duty cycle.
If you use the fan by it self, so without the Rpi, and you connect the ground and the pwm pin to each other, does it work or is the fan running at lower speed?

The other possibility is that you need more current for the base of the transistor. But I didn't calculate that.

By the way, it could be that you need to invert your pwm signal. What I mean by that: 0% == 100% and 100% == 0% (Rpi <> fan)

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 5:13 pm

Hi,
this with the invert is right but not the problem atm^^

I test what u said, so 12V from the Powersource to the Fan Vin and GND from the Powersource to PWM Signal and Ground from the Fan.
He is nor running than.

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 5:21 pm

Okay, thats a good sign.
This means that when you add a low duty cucle the fans is not running any more.

So the issue is somewhere around your transistor. Do you have a LED and resistor. You can test if you can dim the LED without the fan connected.
(5V -> resistor -> led -> collector)

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 5:37 pm

i will try this tomorrow.
Thanks

Ch3fk0ch
Posts: 58
Joined: Tue Apr 05, 2016 8:34 pm

Re: Raspberry(3b+)-PCA9685-12V Fans

Sun Sep 09, 2018 6:19 pm

Ok, i cant wait^^ i made it like this:
BC-238.jpg
BC-238.jpg (92.53 KiB) Viewed 481 times
And i can dimm the LED.

Brandon92
Posts: 473
Joined: Wed Jul 25, 2018 9:29 pm
Location: Netherlands

Re: Raspberry(3b+)-PCA9685-12V Fans

Mon Sep 10, 2018 5:26 am

It's not exactly what I ment, but okay. I think you are using a serie resistor for the led? And I connected it without the fan.

What is the code that you are using?

Return to “Beginners”

Who is online

Users browsing this forum: No registered users and 39 guests