Questions tagged [pwm]

Pulse-Width Modulation (PWM) is a technique used for controlling the power given to electrical devices. The average power supplied is controlled by rapidly turning the supply on and off. Questions here concern driving PWM outputs from the Raspberry Pi.

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Using GPIO PWM with sysfs

I'm able to write to GPIO pins with sysfs with the standard commands like echo "1" > /sys/class/gpio/gpio6/value, but that only turns the pin on or off. I tried echo "0.5" > /...
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4answers
896 views

Can unstable PWM timing be corrected?

I would like to set the motor speed of a RPLidar A3 which requires a 25 kHz PWM. So I played around with the following: from RPi import GPIO GPIO.setmode(GPIO.BCM) GPIO.setup(12, GPIO.OUT) pwm = GPIO....
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2answers
48 views

38kHz, 50% duty cycle PWM output on GPIO

I'd like to generate 38kHz & 50% duty cycle PWM signals on multiple GPIO pins. Hence hardware PWM won't work for me. Does anyone have a chance to generate this signal by using python or node.js? ...
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1answer
35 views

PWM input to raspberry pi 4B

I want to read PWM output signal which I got from a sensor. Is there any way to give PWM signals as input to Raspberry pi 4B?
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1answer
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PWM transducer won't update frequency

I'm creating a simple script that outputs a text input to morse with an LED and a transducer via the GPIO pins on a Raspberry Pi 4 Model B. I tried to add input functionality with buttons that can ...
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1answer
23 views

What is a 'func' in PWM configuration?

To enable PWM on RPI, you need to modify /boot/config.txt. I found nice examples of what line I should add for various cases: https://github.com/dotnet/iot/blob/main/Documentation/raspi-pwm.md I do ...
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1answer
33 views

How do I change the PWM GPIO port in the sine_wave_pwm sample application of pico-playground?

This is the sample code in question: https://github.com/raspberrypi/pico-playground/tree/master/audio/sine_wave I cannot see where it has set it's PWM output pin. Inside "..pico-extras\src\...
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0answers
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RaspBerry Pi pwmchip0 doesn't always work

I'm in a project currently using the RPi's pwmchip0 to implement Hardware PWM. I added the dtoverlay = pwm-2chan in the cofig.txt. Now when I follow that explanation https://jumpnowtek.com/rpi/Using-...
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1answer
48 views

Speed control for a generic 12v fan using Pi Zero

I am trying to speed control a generic 12V 2 pin computer case fan (80mm x 80mm x 15mm). I have purchased an Adafruit TB6612 1.2A DC/Stepper Motor Driver Breakout Board and a Raspberry Pi Zero W. I ...
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1answer
59 views

Issue with DMA+PWM based signal generator

I want to generate some signal on GPIO pin on Raspberry PI Zero W using DMA control blocks and PWM to pace data. However I faced with some problems while trying to generate signal at ~10-50kHz. When I ...
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1answer
48 views

GpioPinPwmOutput set pwm value with floating point

I have a raspberry pi 4 B and I want to control servo motor. I am using NetBeans IDE and Java programming language with pi4j library for raspberry. Also I have a servo motor that can rotate for 300 ...
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How to set PWM frequency below 1Hz on RPi?

does anybody know how to generate a PWM with less than 1Hz of frequency on Raspberry Pi? I'd like to generate a PWM with 0.1Hz if possible. Thanks in advance!
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2answers
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raspberry pi fan don't start to spin without hand help!

Raspberry Pi has recently added fan control feature in its raspi-config tool. This made me curious to add a fan to my RPI 4. I did it recently with a 680-ohm resistor, 2N2222 transistor, 1N4007 diode, ...
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1answer
43 views

Best GPIO API for high data rates and frequencies?

Using RPI3B+. I need to have 2 pins (a clock and data) to write data to shift registers on frequencies of 1,76 MHz or rate of 1,76 Mbps, and 1 pin(connected to GPIO 18) on 20 kHz. Tested RPi.GPIO.PWM ...
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56 views

Do GPIO 12 and GPIO 18 share the same frequency since they are the same channel?

Using RPI3B+. I already use GPIO 12 (the other PWM channel 0 pin) for a ledstrip. [Question: Can I use GPIO 18 on a different frequency, or do GPIO 12 and GPIO 18 share the same frequency when used as ...
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Noise on interrupt pins while using Hardware PWM

i have been using the RPI4 to control 2 brushless motors with encoders, using 2 PWM signals to the motor driver, and reading both 3.3 V encoders(2 channel resolvers each) using interrupts. If i move ...
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Hardware Timed Servo PWM

I am working on a some time-critical system that will run image processing and controlling 4 SG90 servo motors. In short, I will do visual-servoing. In this topic, joan pointed out some library, ...
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1answer
41 views

Controlling 4 servo motors through hardware PWM

I am working on a some time-critical system that will run image processing and controlling 4 SG90 servo motors. In short, I will do visual-servoing. Since I will do visual servoing, I don't want to ...
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0answers
32 views

LED strip works through Arduino PWM, but not Raspberry Pi PWM

I've been stuck on this for a while. I'm following a simple tutorial for RPi-controlled LEDs. From this, my LEDs do random stuff and don't light up correctly. I've been trying strandtest from this ...
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1answer
34 views

What is the relationship between angles and pulse length of servo motor?

I've been working on a project where I've to drive the servo motors. I am using Raspberry Pi 3B+ model and Adafruit PCA9685 to drive the servos. For that I need to find which angle is at what pulse ...
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1answer
28 views

Controlling WS2812 with a non-PWM pin

I was looking for a way to control WS2812 led without PWM pin (specifically I would use pin 4 (1-WIRE pin) to control WS2812). Is it possible? Thanks
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Beginner question: Bad results with WS2812B and strandtest.py

I have a setup for testing my WS2812B led strip with the raspberry pi. I am following the AdaFruit best practice guide Including using the recommended level shifter after the pwm pin. I've included ...
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0answers
106 views

How to make/get a proportional flow control valve [closed]

I want to use hydraulic flow to proportionally vary the resistance of a rpi controlled exercise machine. The victim would rotate a positive displacement pump where the inlet and outlet ports are ...
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2answers
75 views

pigpio scrambles hardware PWM signal

I'm using a dedicated library to run a ws2812 led strip. As far as I understand, this library sends a signal using the hardware PWM, via GPIO pin 18. This works fine and the led strip shows the colors ...
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1answer
38 views

Sending Square Waves to more than one gpio pin with pgpio

I've been searching around for a few days and couldn't find a solution to this problem. I'm using the pgpio library that is native to the RPi4 and been looking all over their website: http://abyz.me....
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3answers
342 views

How to use Rpi python GPIO pins in PWM output mode to create PWM signals?

I was trying to understand PWM when I ran across this example: import RPi.GPIO as GPIO GPIO.setmode(GPIO.BOARD) GPIO.setup(12, GPIO.OUT) p = GPIO.PWM(12, 0.5) p.start(1) input('Press return to stop:')...
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1answer
110 views

RPi PWM issues - (re)start results in oscillating pin

I'm building a sauna controlling mechanism, controlled by the Pi, using PWM and solid-state relays. Works fine, but after a while, the PWM breaks down. At this moment, when I run the program and the ...
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1answer
82 views

Turn on an LED with dimming and stay on

I want to start the LED gradually with dimming by using PWM. And then once at a ChangeDutyCycle(100) I want it to remain on GPIO.output(led, GPIO.HIGH). import RPi.GPIO as GPIO import time led = 17 ...
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2answers
134 views

How to create unfazed pwm signals?

I have two pins with the same frequency (10Hz) and same duty cycle (50%) assigned to two different leds. How can I make the two leds blink alternatively? How can I put a delay of 50% in one of the ...
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1answer
208 views

Raspberry Pi Software Driven servo control with PWM using C and Wiring Pi LIbrary

I'm trying to get my raspi zero to move an SG90 PWM driven servo. I have achieved this with python already using the gpiozero library, so I know my hardware works but I am trying to do it with C using ...
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1answer
290 views

How to control a Servo via libgpiod on a raspberry PI

I am trying to control a Servo in c ++ using the libgpiod library. My problem is in defining the 50Hz pwm pulse on the pin that the servo is connected to. The servo signal cable is connected to pin 33 ...
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2answers
609 views

PWM frequency/profile for "official" pi fan?

I have a pi4 with the "official" fan case and I would like to write my own fan control code. I have looked online for a datasheet for the fan but haven't found it yet. I see on the case fan ...
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1answer
81 views

Reading current PWM output configuration

I use gpio #32 (wPi #26) as PWM output to control the speed of a fan based on temperature. The job starts at system startup with a dedicated account. I would like to display the current value that is ...
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1answer
116 views

Set different frequencies for the two hardware PWMchannels on PI 4B

I'd like to generate two PWM signals with SAME duty cycle (50%) but DIFFERENT frequencies on raspberry pi 4B. The difference between the frequencies is within +/-80%. The two GPIOs I'll use are GPIO ...
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2answers
2k views

Control a 12V dc fan via PWM and a level shifter

I wish to control a 4 pin 12V dc pc fan (https://www.arctic.ac/en/F9-PWM/AFACO-090P2-GBA01) with my raspberry pie. After reading several threads I came up with the following: First problem is that the ...
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0answers
54 views

Redirect Rpi Audio/Mic to Sim module

Raspberry Model: Zero W. External Modules: SIM800L Image Adafruit I2S MEMS Microphone Breakout Small Audio Speaker I'm aiming to make phone calls with the sim800L and 'bind' them with the RPI and I'...
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1answer
106 views

Sending a NEC like signal via a GPIO

I'm trying to control an existing LED strip controller with a Raspberry Pi. The controller has an IR receiver to receive commands. I removed the IR receiver of the controller and added a connection to ...
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1answer
200 views

Trouble getting sg-90 servo to work with R-PI 4

I have read several answers and approaches to controlling an SG-90 servo with a raspberry pi and I have tried the following approaches, with varying but never satisfactory results. Wiring Setup: ...
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1answer
263 views

What values for PWM to set intensity from 0 to 255?

I am using hw-479 that looks like the picture below. I cannot find much of information for it but the Alibaba page says The RGB LED module is made of a plug-in full-color LED. The PWM voltage input ...
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0answers
132 views

Powering a Servo with 12V Battery and Buck Converter

I wanna power my servo with the 12V terminal of a Mastercraft Nautilus battery pack (see here)(long story). The servo is a actuonix pq-12 micro linear servo (see here). I'm stepping the voltage down ...
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1answer
78 views

Controlling LED using PWM

When I run this code I’m expecting to get a led that brightens but I get a led that dims. import RPi.GPIO as GPIO import time GPIO.setmode(GPIO.BOARD) GPIO.setup(11,GPIO.OUT) dc=0 LED=GPIO.PWM(11,...
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0answers
63 views

When i change the dutycycle on my PWM it doesnt move my servo

I am using an SG90 and the GPIO Pin #17 but it only sometimes turns when I run the code. It always works if I reset the Kernel everytime. I am connected to my Pi through putty and am running the code ...
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2answers
942 views

PWM issues with pigpio and RPi.GPIO

I am using Pi Zero W with latest Raspberry Pi OS. I have a backlight of an LCD that I am trying to control via PWM. If I use RPi.GPIO I get flicker at anything other that 100% (or 0%) duty cycle. As ...
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0answers
42 views

Raspberry Pi3 - Controlling 4 DC motors

I need to feed 4 DC motors of 5V on my Raspberry Pi 3 Model B using PWM (Pulse Width Modulation). Currently, I have the next components: 2 NPM transistors, 1 L293D integrated circuit, resistors (220 ...
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0answers
367 views

Rpi python with a PCA9685 PWM controller stopping a digital servo motor problem

I have several servos plugged into a PCA9685 board and controlling them with PCA9685.py, and at the end of the script at pwm.cancel() my SF3218MG (270 degree) and 6221MG (180 degree) servos turn off ...
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1answer
141 views

PWM problem in a frequency less than 100Hz

I have attached a fan to pin #17 (through a transistor of course) and am writing a script to turn the fan on for a specified duration with a specified PWM duty. #!/usr/bin/env python import os ...
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1answer
97 views

Issues with Throttle Control on ESC with RPi 3B+

I am using the 30A BLDC ESC to control a brushless motor from my Raspberry Pi 3 B+. The documentation for the ESC can be found here: ESC pdf I seem to have successfully calibrated the ESC, but after ...
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0answers
186 views

Using pigpio and hardware PWM simultaneously

I am using pigpio to read 4 inputs. Everything works fine. And the entire process is a bit long and memory consuming. I also have to use one PWM output. I am planning to use the hardware PWM (pin 12 ...
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1answer
133 views

PWM not reaching desired frequency after checking on oscilloscope

I am attempting to setup a PWM signal on Pin 12 (GPIO #18) using a Raspberry Pi 3. I am capable of sending a PWM signal, however it is quite off from the target frequency. I have an o-scope that I ...
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0answers
268 views

pigpio hardware PWM for servos

My goal is to build a pan/tilt system. this works fine: import pigpio pi = pigpio.pi() pi.set_servo_pulsewidth(13,1055) 2 questions: is pi.set_servo_pulsewidth using hardware PWM (I prefer HW PWM) ...

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