Hardware PWM Node-Red

General
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1

Hi

I'm looking for a way to use fully hardware PWM on my RPi Zero.
I want to control a PWM fan requiring 28 kHz.
The GPIO PWM nodes are software only (?).

Does anyone have a script to control the PWM signal through red node?

2

Hi Sleep,

you can use this module:
This is a 1Hz-150Khz Signal Generator Modul.

s-l1600
s-l16001600Ă—1600 158 KB

s-l1600
s-l16001600Ă—1600 138 KB

They have RX and TX inputs.
Connect only to RX with 9600bps, 1 stop bit.
Send string "F28.0" for 28kHz.
Send string "D050" for 50% duty.
Use serial node in Node-Red.

3

It's not possible without this additional hardware?
Would it be possible to create the PWM with RPi hardware?

4

You can use this python library that support this frequency:

But it is not used in any Node-Red node.

5

I'm completely new to this stuff.

Could you make a script for me and tell me where to run it?

:frowning:

6

Does node-red-node-pi-gpiod use that?

7

Oh yes @Colin, it use the pigpio, sorry.
Node-Red has 4000 nodes and it isn't easy to remember all.
@Sleep I think you can use it for 28 kHz.
An other question: Which hardware do you use for driving PWM fan because the gpio drive only 16mA ?

8

The node-red software generated pwm is not available for these higher frequencies. I havent figured out how to use the RPis build in hardware to generate 28k.

9

Yes the pigpiod node uses that Pigpio library which can use hardware pwm, so use that node rather than the default pigpio node