Pigpio commands into NodeRed

General
1

Hello,
I'm looking for a way to insert following terminal commands into NodeRed:

sudo pigpiod
python
import pigpio
pi=pigpio.pi()
pi.hardware_PWM(12, 25000, 1e6*0.25) # 25000Hz 25% dutycycle(normaly)

The whole thing is a fan control and the 0.25 are the duty cycle and should be infinitely adjustable.

Can someone help me plz?

2

Hi,

a) you can't (easily) run a command as sudo as that is a security privilege escalation. so you need to run pigpiod outside of Node-RED. However once you have done that then
b) there is a node-red-node-pi-gpiod that can drive it for most use cases - https://flows.nodered.org/node/node-red-node-pi-gpiod

3

Hi,
i know this node but i have to run it with the 25khz and there is no option to change it.

4

If the pigpiod daemon is running then you might be able to set the frequency by calling your exec node using this (not tried but worth a go)

import pigpio
pi=pigpio.pi()
set_PWM_frequency(12, 25000)

NB pigpio doesn't let you choose any frequency value

image
image.png656Ă—916 36.3 KB

but is the fan really that sensitive to the frequency?

1 Like
5

Hi,
thanks.

And yes, they are^^

6

seem not to work.
Another idea:
A Pythonscript with a variable (DutyCycle), but also there I do not know yet really how I should convert it...

7

Just checking - what physical pin is your fan connected to
Node-RED uses physical pin numbers so if your connected to pin 12 then you need to use

set_PWM_frequency(18, 25000)

as physical pin 12 is gpio number 18

8

Just tried it out on a PiZero and it seems to work - with correct syntax that is :slight_smile:

I created a file called fred.py

image
and stuck this in it

import pigpio
pi=pigpio.pi()
pi.set_PWM_frequency(18, 25000)

And injected value of 25 into the pigpio node
image

I've put an LED on the pin and it glowed as expected

I then changed the fred.py to

import pigpio
pi=pigpio.pi()
pi.set_PWM_frequency(18, 5)

and this time the LED blinked rapidly

So I think that proves the concept is good :slight_smile:

9

Well it doesn't work for me. I get the following error message from exec:

11.8.2019, 21:22:47node: ac7e4461.29989msg.payload : string[0]
""
11.8.2019, 21:22:47node: ac7e4461.29989msg.payload : string[144]
"Traceback (most recent call last):↵ File "/home/pi/scripts/test.py", line 2, in <module>↵ import pigpio↵ImportError: No module named pigpio↵"
11.8.2019, 21:22:47node: ac7e4461.29989
msg.payload : Object
{ code: 1, message: "Command failed: python /home/p…" }

pigpio is runnig cause pigs hp 12 25000 500000 works but the python part dont.

>>> import pigpio
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: No module named pigpio

I'm a bit confused

10

Do you get same error if your run

python /home/pi/scripts/test.py

from plain terminal command line?

11

yes

pi@octopi:~ $ python /home/pi/scripts/test.py
Traceback (most recent call last):
  File "/home/pi/scripts/test.py", line 2, in <module>
    import pigpio
ImportError: No module named pigpio
12

That IS wierd :frowning:

Luckily you can directly call pigs

image

(My LED is on pin 12 - gpio 18)

1 Like
13

Hello,
yeah, that's what I'm playing with right now.

All I have to do now is figure out how to get a number from the inject block into the output.
So I would have to
pigs have hp 12 25000 500000 where the 50000 should come from an input.

14

You can use incoming msg.payload and get it added onto the end :slight_smile:

image

Just make sure to add the space at the end

15

Ah ok, Thanks it works xD

2 Likes