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I2C PCA9685 Output? #170

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opened 2018-07-14 21:11:28 +01:00 by Ch3fk0ch88 · 6 comments
Ch3fk0ch88 commented 2018-07-14 21:11:28 +01:00 (Migrated from github.com)
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Hello,
is it possible to control a PCA9685 (PWM FAN CONTROL) as Output?

Thanks

Hello, is it possible to control a PCA9685 (PWM FAN CONTROL) as Output? Thanks
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vitormhenrique commented 2018-07-15 16:27:59 +01:00 (Migrated from github.com)
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No, but if raspberry pi already has some "pwm" what would be the advantage of an external IC? do you want to control 16 fans?

No, but if raspberry pi already has some "pwm" what would be the advantage of an external IC? do you want to control 16 fans?
Ch3fk0ch88 commented 2018-07-15 17:25:21 +01:00 (Migrated from github.com)
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2 Fans are allready heavy for the Gipos.
Also u cant run stronger fans over 15mA. Or is there a pwm "booster" that boost the pwm signal of an Raspberry?

2 Fans are allready heavy for the Gipos. Also u cant run stronger fans over 15mA. Or is there a pwm "booster" that boost the pwm signal of an Raspberry?
vitormhenrique commented 2018-07-16 15:24:47 +01:00 (Migrated from github.com)
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You should NEVER NEVER NEVER plug a dc motor (that is what basically a fan is) directly on your raspiberry pi, motor is a big inductor, that can generate big voltage spikes, and it is very likely to fry your raspberry pi! You need to use a mosfet and a fly back diode to properly drive PWM fans. That basically is how you "boost" and drive motors, with an external power supply, or direct +5V connected to the motor.

Read the following:
controlling using a transistor / mosfet.

You should **NEVER NEVER NEVER** plug a dc motor (that is what basically a fan is) directly on your raspiberry pi, motor is a big inductor, that can generate big voltage spikes, and it is very likely to fry your raspberry pi! You need to use a mosfet and a fly back diode to properly drive PWM fans. That basically is how you "boost" and drive motors, with an external power supply, or direct +5V connected to the motor. Read the following: [controlling using a transistor / mosfet](https://circuitdigest.com/microcontroller-projects/controlling-dc-motor-using-raspberry-pi).
Ch3fk0ch88 commented 2018-07-16 19:36:04 +01:00 (Migrated from github.com)
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Its not connected directly to the Raspberry.
I use 4PIN PWM Fans (PC Case Fan's like Noctuna).
So u connect the 12V and the GND to a DC Power Supply and the PWM and Speed signal to the Raspberry.
But the Raspberry PWM signal has not enough current to run bigger PWM Fans.

Its not connected directly to the Raspberry. I use 4PIN PWM Fans (PC Case Fan's like Noctuna). So u connect the 12V and the GND to a DC Power Supply and the PWM and Speed signal to the Raspberry. But the Raspberry PWM signal has not enough current to run bigger PWM Fans.
vitormhenrique commented 2018-07-16 20:00:52 +01:00 (Migrated from github.com)
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same thing apply: you can just use the 5v from rpi supply and a transistor to increase the current capabilities of rpi pwm...
Also, those fans like to be controlled by a 25kHz signal, default value on the plugin is set to 50Hz.
Your issue can be easily fixed with hardware.
I could implement PCA9685 on the future, but it is not going to be a near future, there are other things on my priority list and don't have a PCA9685 on hand to implement and test the feature.

same thing apply: you can just use the 5v from rpi supply and a transistor to increase the current capabilities of rpi pwm... Also, those fans like to be controlled by a 25kHz signal, default value on the plugin is set to 50Hz. Your issue can be easily fixed with hardware. I could implement PCA9685 on the future, but it is not going to be a near future, there are other things on my priority list and don't have a PCA9685 on hand to implement and test the feature.
Ch3fk0ch88 commented 2018-07-16 20:14:47 +01:00 (Migrated from github.com)
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Did u maybe auf time to make a little circuit diagram?
This PWM stuff isn't really my area of expertise.

Otherwise I use as an alternative simply a 2-3Pin fan and control the voltage via a MOSFET which is controlled by the Raspberry PWM^^

Did u maybe auf time to make a little circuit diagram? This PWM stuff isn't really my area of expertise. Otherwise I use as an alternative simply a 2-3Pin fan and control the voltage via a MOSFET which is controlled by the Raspberry PWM^^
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Reference: Gandalf/OctoPrint-Enclosure#170
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