Arduino PWM Tutorial #1 - How To Change PWM Frequency
ฝัง
- เผยแพร่เมื่อ 30 ก.ย. 2024
- The Arduino has a fixed PWM frequency of 490Hz - or does it? On digital pins 3, 9, 10 and 11 it's 490Hz, but on pins 5 and 6 it's 976Hz. Confused?
And it is possible to change the PWM frequency to a higher (or lower) frequency by altering the timer prescalers. Here's how it's done.
Thanks Shaun. I found a very nice PWM library (shown in my part2) which sets up all the registers and has a 'safe' mode to protect millis() and delay() by not changing anything related to Timer0
Yes, delay() and millis() are affected by changing the prescaler for timer0. If you want to avoid that, you should change timer1 and/or timer2 instead. Not sure what side effects would result from doing that though - anyone know?
/*
Prorotype Code for 1-4MHz PWM 50% Duty Cycle
ICR1as TOP = crystal / (2*Prescale*Fpwm) in MODE 9
at 16000000MHz 64 Prescale PWM Fmax = 62.5KHz
at 16000000MHz 8 Prescale PWM Fmax = 500KHz
at 16000000MHz 1 Prescale PWM Fmax = 4MHz
*/
void setup(){
pinMode(9, OUTPUT); // OCR1A Output
pinMode(10, OUTPUT); // TEST Pin 10 as General purpose that can use after Enabling only OCR1A
digitalWrite(10, LOW);
delay(1000);
digitalWrite(10, HIGH);
//phase/frequency correct mode. SELECT THIS FOR INVERTED OUTPUTS.
TCCR1A = _BV(COM1A1); // Enable OCR1A none inverting mode
//TCCR1A = _BV(COM1A1) | _BV(COM1B1) ; // Enable OCR1A and OCAR1B and none inverting mode
// TCCR1A = _BV(COM1A1) | _BV(COM1B1) | _BV(COM1A0) | _BV(COM1B0);
//TCCR1B = _BV(WGM13) | _BV(CS11); // Set Prescale Clock 8 and Mode 9
TCCR1B = _BV(WGM13) | _BV(CS10); // Set Prescale Clock 1 and Mode 9
}
void loop(){
//ICR minimum 2 F = 16000000MHz No Change if using 14745600MHz
//make this variable as table
//ICR1 = 10,000; // 100Hz w/16MHz Prescale 8
//ICR1 = 5,000; // 200Hz w/16MHz Prescale 8
//ICR1 = 2; // 500KHz w/16MHz Prescale 8
ICR1 = 2; // 4MHz w/ 1600000MHz Prescale 1
OCR1A = ICR1 / 2; // 50 Duty of ICR1
}
Bey Meephanlom
just a suggestion! ..
well u might think that a pencil is harmless when u use it to point adruino pins.
But unfortunately graphite(pencil lead) is a conductor of electricity.. so be careful👍
void setup() {
TCCR2B = (TCCR2B & 0xF8) | value;
}
For the lazy, just change "value" for 1 to 7 according to this:
31372.5 Hz -> 1
3921.57 Hz -> 2
980.392 Hz -> 3
490.196 Hz -> 4 (default)
245.098 Hz -> 5
122.549 Hz -> 6
30.6373 Hz -> 7
hello. Thank you i dont speak enghlish i have a question if i want set frecuency to 62.5 khz ¿ i can with arduino nano but not in the timer 0 (for the millis and delay)?
I tried this and works perfectly as you said. Very helpful. A thousand thanks
i don't get why it is so hard to change the frequency, I still don't get how it works and have to copy pre made code
video: 11 minutes
info: 10 seconds
useful stuff starts at 9:00
Great stuff. You highlight one of the many abstractions that Arduino programming language/IDE manages for users in the background. I'm guessing that it may be easier to go straight to C programming for the PWM and Timer peripherals where the full power of all the options are available. But then it wouldn't be an Arduino topic. Thanks for your videos and clear instructions!
Thank you so much Julian, it's a excellent tutorial.
Regards from Colombia!
Was fumbling around for 3 days looking for this. This will help on my arduino audio school project. Thanks!!!
Thank you Julian , I fixed that ugly humming noise of a dc motor by changing the frequeny , now it is even more controlable and really quiet.
What frequency did you use? I'm using 976 HZ (pins 5&6) currently and the dc motor sound is annoying at low PWM.
Very helpful man you are, thank you.
Its varying the duty cycle 🥲
hello i was wondering if you would be able to help me.i have puls generator.how can i program it to run 10% duty cycle at 0.64 v input and gradually increacing voltage to 3.86v with duty cycle 90%.its for my project where voltage coming from throttle position sensor potenciometer control my pulse/duty cycle generator which then directly control fuel injector.any advice most appreciated cheers joe
Plz code 3-phase
THANK YOU. This is huge for driving any non-trivial load off an Arduino pin. For an LED, it's fine. But if you want to drive some other entire circuit module, maybe some transistor circuit, etc, and you need to approximate smooth DC, a PWM at high frequency can very efficiently and simply be filtered to reasonably smooth DC with a small cap and resistor, much more easily (and with quicker response) than low freq 490 Hz PWM.
setting pins as output is usually a good idea if you've had another sketch previously on it, setting it as an input. This is how pins are destroyed. It's not necessary just good practice.
How can you change the exact frequency to 10khz?
I did that in the follow up video
Julian Ilett Hey Julian, my friend created a non-overlapping pwm signal by using PIC18 without any extra hardware. Have you tried it with PIC? I mean how is it non possible with an Arduino?
will u give me the link of follow up video for 10 khz cuz i didnt find it in ur channel i wana generate 20 khz pwm
enjoy
th-cam.com/video/9JXGIeM3BSI/w-d-xo.html
when I load ver5 pwm iI could not get it to work keep getting message "Error compiling for board Arduino /Genuino Uno"
I think you'll find that the discrepancy between the expected and measured nominal 31Khz frequency at the end of the video is down to being on too slow a 'scope range, if you set to 1us/div you'll likely be closer to target.
Chat to find code 6:25
Hello, does anyone knows where I can download a copy of the header.h file, as Julians website has been down now for some time? I need a copy to be able to compile and upload to Arduino Nano.
with the last included codes, will produce 50kHz frequency from arduıno as a PWM pulse.?
Can I take from arduino, PWM with duty cycle 20% and frequency 10Khz or 20 khz???
if you used a different frequency crystal to control the clock speed of the chip, wouldn't that change the frequency for the pwm output?
Sir very informative...
Hi Julian, I used this info on one of my projects to eliminate audible noise that I was getting at the lower 976hz. Thanks for sharing, regards Roger
changing timer prescaler affects to some functions such as delay() or servo library ?., Thanks
Does the nano have the capability to read a frequency and control a device based on that frequency as it changes?
Hey man
I have a question, is it possible to work PWM at low frequencies? on the order of 4 to 10 Hz? Greetings man
This is many moons old, but would like to ask how you got the PWM library to install. I've had no luck!
Tried installing from manage libraries but it doesn't show up and tried the include library/zip file from the sketch. Just says the PWM.h file doesn't exist. Most frustrating.
Ignore my message. I did that thing that you should never do, and that's actually take notice of what the error says. All sorted and will compile now. Ooops
can pwm frequency be changed in an arduino uno similarly??
How can I set the output to 20 kHz in arduino mega please I need your help
how can you change the arduino prescaller to 8 of a timer ? hmmm
Can you run HDD ~18000RPM
With controlled speed
By this arduino
I will pay for this
It's part of my huge project..
If u can then plz ...
how to change frequency upto 50hz?
Hello
can i reduce frequency to 10hz
great! i would use 62k for a class d projet
Hello. Is it possible to switch multiple frequencies with switches ? For exampe i want to drive a DC Motor with 500HZ, 1000Hz and 2000HZ , but i dont wont to change the code every time, but to change it with a switch mechanical. Is there a possibility to program a code witch recognizes witch switch i turned on, so the PWM works with the frequency. Sorry for my bad english.
You simply change the pwm %
pwm frequency has no impact on the speed of your motors
@3.05 you say that the pin D13 is missing, it's actually located on the down-left side of the arduino, just look for it. Great video nonetheless.
I think he meant that he was wishing that D13 was a PWM channel, since it already has an onboard LED. Would be handy for experimenting.
How can I set the output to 130 Hz? I tried running the sketch in Tutorial #2 but it won't compile, it's worthless!
I see that your question is from a few years ago, and I am honestly just beginning to understand how to manipulate these frequencies. But I wonder if changing the clock speed would allow us to have more control over a wider range of frequencies? Hopefully I don't sound too illiterate to you. Mostly I hope you have since solved this issue but as a beginner, trying to think this through seems to be helping me to grasp the concepts at a deeper level. Maybe I'm even close. Would love to hear what your solution was to this problem. Cheers!
LOL, you cooked the track I bet.
Nice!
if you need two output frequencies can you program the second to have a 90 deg phase shift?
Yes, I think so. I'm going to produce a video on that quite soon. It's for a charge pump circuit where I want two PWM signals 180° out of phase, but 90° would be just as easy to implement.
I'm designing a voltage controlled phase controller for AC lamp dimming that I intend to drive via an Arduino Uno. I'm attaining an analog voltage by passing the PWM outputs through a simple R/C network to generate a constant voltage proportional to the duty cycle of the PWM signal. To get a voltage output that changes fast but still has no noticeable ripple, I need a high frequency PWM signal. I've had this prescaler change work on both timers 0 and 1 of my Arduino Uno, giving me adequately high frequencies for my project. The only problem is, serial communications rely on timer 0, and the Arduino needs to be controlled via serial. This being said, most people would think that using timer 2 would be the obvious answer. So did I. However, when I set the prescaler of timer 2 to 1, PWM on pins 3 and 11 stopped working all together. an analog value from 0 to 254 yielded a logic 0, and 255 yielded a logic 1. Can anyone tell me why changing the prescaler on timer 2 of the Arduino Uno doesn't work? Am I doing something wrong, or is it just not possible to do? Thank you for any help!
Nevermind the issue stated in the last comment. I made a silly mistake. Well, in essence, so did the sources for how to change PWM speeds. They all say to use a code like this:TCCRnB = TCCRnB & 0b11111000 | mode;with mode being the prescaler setting. That works great for timers 0 and 1, because their mode is 3, or 011 in binary. since we're increasing the speed, setting one of those two LSBs to 0 will change their state as seen by a truth:011 & 010 = 010011 & 001 = 001011 & 000 = 000 (noting that this shuts off the PWM all together)However, timer 3 has an initial prescaler of 4, or 100 in binary, so a speed increase will yield these truths:100 & 011 = 000100 & 010 = 000100 & 001 = 000100 & 000 = 000As you can see here, using the commonly given code for prescaler alteration, an attempt to increase the speed will simply disable the PWM for 3 and 11 all together, hence my problem. A simple solution is to change the line of code to this:TCCR2B = TCCR2B + (4 - mode);with mode still being the same prescaler values.Setting mode to 1 will subtract three from the original value of TCCR2B without affecting anything beyond the prescaler values, so, knowing that 100 in binary is 4 in decimal, we can calculate the new prescaler:TCCR2B + (4 - mode)4 + (4 - 1) = 4 + -3 = 4 - 3 = 1I have tested this new code, and it does in fact work for the Arduino Uno PWM pins 3 and 11. The code can also be altered for TCCR0B and TCCR1B as such:TCCRnB = TCCRnB + (3 - 1);NOTE: once the timer speed has been altered using this code, altering it again with the same code will yield errors. This could be remedied with a code like this:int oldPrescaler = x; //set x to 3 for TCCR0B/TCCR0B, and 4 for TCCR2B
void setPWMSpeed(newPrescaler){ TCCRnB = TCCRnB + (oldPrescaler - newPrescaler); oldPrescaler = newPrescaler;}This code will automatically compensate for a previously set prescaler if you should ever wish to change it again during a program.Noting how this hasn't been covered anywhere on the internet that I can find, I hope this helps anyone else stuck on the same issue!
I apologize if the code is confusing in line with the text, I forgot that TH-cam does that in comments. If you need any piece of the code in proper format, I can email you a text file of it. Happy coding!
A link to the tables would be nice :-)
Just a quick question. Is the analogWrite duty cycle pre-established. I am going for a 50 percent duty and I am generating the 31khz from D9 like you showed in your video. Thank you.
analogWrite(pin,duty) is the syntax for the function. Duty is a scaled input from 0-255. 0 commands a 0% duty cycle, 255 commands 100%. For 50 percent enter 127.
+backcountry52 Thanks for the info. I really appreciate it. Cheers!
can all 6 pwm run on same frequency of about 10khz?
I have a related question that I am currently in the process of attempting to understand. I would like to know if each PWM channel, can output a different frequency simultaneously. For example, have Pin5 send a lower frequency to one motor, Pin9 send a somewhat faster frequency to a 2nd motor, and also have Pin11 send a higher frequency to a third motor?
This is awesome. thanks for sharing
Thank you for this very clear and useful lesson!
Hudge thx to you.
I'm trying to run an rgb led off pins 3 5 and 6 but thinks pins 5 and 6 are the same why is this happening
+Troy Dry pins 5 and 6 use the same internal timer
Excellent as usual
Thanks Jullian.
Very helpful
Thank u so much
thanks a lot
very
how to have code
Adrien Feudjio Temgoua yep je know mais sa dependra exactement du type de projet
When you change frequency and after that upload different sketch, does it set PWM frequency to default?
I think its changed to that speed when the sketch runs, thats how I understand the underclocking process.
hi Julian, i have been watching your video but i got questions. it is really possible to change the frequency of pwm up to 500kHz or it is limited up to 64kH on pin 5 and 6?
thank you.
I think you can go to quite high frequencies, but you will lose resolution. So at 500kHz you may only get 3 or 4 different pulse width values.
Padding resistors should always be used at each end of a pot to stop short outs say 1k0 or lower but love your Arduino Videos
Bob