Go Down

Topic: Led PWM driver high peep sound (working) (Read 305 times) previous topic - next topic

Kumalix

Hi,

I have this nice little board:
https://docs-emea.rs-online.com/webdocs/1373/0900766b81373236.pdf

It's the one with 1000mA.

Using PWM wemos function i get the 10W led dimmed but the driver has a very high beep sound.
When off and full on it doesn't beep. Only when when the led gets dimmed a bit.

This is the simple PWM program i use:

Code: [Select]
/*
 * Copyright (c) 2015, circuits4you.com
 * All rights reserved.
/* Generates PWM on Internal LED Pin GPIO 2 of ESP8266*/

#include <ESP8266WiFi.h>
#define LED D4

int brightness = 0;    // how bright the LED is
int fadeAmount = 5;    // how many points to fade the LED by

//=======================================================================
//                    Power on setup
//=======================================================================
void setup() {
  Serial.begin(115200);
  pinMode(LED,OUTPUT);
}

//=======================================================================
//                    Main Program Loop
//=======================================================================
void loop() {
  analogWrite(LED,0);
  delay(3000);
 
  analogWrite(LED,102);
  delay(3000);

  analogWrite(LED,205);
  delay(3000);

  analogWrite(LED,410);
  delay(3000);

  analogWrite(LED,714);
  delay(3000);

  analogWrite(LED,1024);
  delay(3000);


//analogWrite(LED,800);

//delay(5000);
  //Continuous Fading
//  Serial.println("Fadding Started");
//  while(1)
//  {
//    // set the brightness of pin 9:
//    analogWrite(LED, brightness);
// 
//    // change the brightness for next time through the loop:
//    brightness = brightness + fadeAmount;
// 
//    // reverse the direction of the fading at the ends of the fade:
//    if (brightness <= 0 || brightness >= 1023) {
//      fadeAmount = -fadeAmount;
//    }
//    // wait for 30 milliseconds to see the dimming effect
//    delay(10);
//  }
}
//=======================================================================


Hope someone can help! I don't understand why it beeps?
Has it something to do with the frequency?

I tried Logic converter like this one: https://benselectronics.nl/txs0108e-level-converter-8-kanaals/
But that doesn't help.

Please help.

tnx

larryd

#1
Dec 16, 2018, 11:16 pm Last Edit: Dec 16, 2018, 11:19 pm by larryd
What Arduino board are you using?

Read this on analogWrite()
https://www.arduino.cc/reference/en/language/functions/analog-io/analogwrite/



No technical PMs.
The last thing you did is where you should start looking.

Paul__B

I have this nice little board:
Nice!  And little.

Using PWM Wemos function I get the 10W led dimmed but the driver has a very high beep sound.
When off and full on it doesn't beep. Only when when the led gets dimmed a bit.
As one would expect as it is switching in and off at an audible frequency.

Hope someone can help! I don't understand why it beeps?
The inductors vibrate.

Has it something to do with the frequency?
Yes, the PWM is an audible frequency.

I tried Logic converter like this one.
But that doesn't help.
No reason why it would as the logic levels have nothing to do with it.

You are not permitted, according to the datasheet, to PWM it at an inaudible frequency (maximum specified 1 kHz) because that would interfere with the switchmode operation.

This is how it works.  Live with it!

No, actually, you could use some extra circuitry with an op-amp to filter the PWM to an analog voltage to suit it, but I do not fancy trying to design that for you.  I suggest - live with it!

What Arduino board are you using?
WeMOS.  He said.

Kumalix

 :)

In the sheet there is a graph with specified frequency and it says 200Hz.

Now when i set analogWriteFreq(200); the sound is less.

Question: Is the 200 in analogWriteFreq(200), 200Hz? Or do i need to recalculate the correct Frequency?


tnx

Wawa

PWM for those type of drivers can be 'zero' to about 1khz.
Higher, and you can't dim very low.
Lower than ~100hz, and you start to see flicker.
About 200hz is a good compromise.
A lower frequency is also generally quieter (coil whine).
Putting the driver inside a case should make it almost inaudible.
Make sure it doesn't get too hot.
Leo..

Kumalix

thx for your explanation.

Is there an alternative PWM driver?
I just can't live with this sound.

Maybe simular board what i can use?
PSU = 24 volts DC.
driving 3x10W (1000mA per led) led's in serie.

tnx for the help!

Paul__B

Now when i set analogWriteFreq(200); the sound is less.
That may well be the optimum.  The lower the frequency, the fewer switching transitions over time, so less vibration.

Question: Is the 200 in analogWriteFreq(200), 200Hz? Or do i need to recalculate the correct Frequency?
Presumably is 200 Hz.  

Actually, in case you have not figured this out already, you could even try 100 Hz.  The light will flicker, but you will not notice it unless there is movement involved.  :smiley-lol:

Wawa

"3*10watt/1000mA LED in series".

That means a LED Vf of ~30volt.
And a power supply of at least 33volt.
What kind of supply are you using. Is it regulated?

That driver also needs at least 4.35volt PWM, something a WeMos can't provide.
I think a MeanWell LDD-1000H would have been a better choice.
Leo..

Kumalix

Hi,

Yes tried 100Hz or lower and it doesn't flicker. But the sound is not lower between 100 and 200 Hz.

That means a LED Vf of ~30volt.
And a power supply of at least 33volt.
What kind of supply are you using. Is it regulated?
this is the PSU: https://docs-emea.rs-online.com/webdocs/1527/0900766b8152741e.pdf

Now i don't really know if it is regulated or not, don't know where to look for that info in the datasheet?  :smiley-confuse:

Is this one ok?

I'm making just a simple lamp.
I want to use 2 of these drivers, 1x PSU (mentioned above) and drive 3*10Watt warm white led and 3*10Watt cool white. With PWM i want to be able to controle the light color.
So all six leds wil never licht at 100%. It wil be 6* at 50% max i think.


That driver also needs at least 4.35volt PWM, something a WeMos can't provide.
I think a MeanWell LDD-1000H would have been a better choice.
Leo..
If i can controle meanwell LDD-1000H with 3.3 PWM of WeMos and it doesn't make any audible noise than i will switch to meanwell. But before i purchase the meanwell can anyone confirm that i can use it with in this project?

Tnx for your help! I really appreciate it! 

N


Smajdalf

If analog dimming makes the sound to go away I think RC filtering of a fast PWM output would be enough. I think it is worth to try.


Kumalix

Stil heard some noise. So made a Low pass filter like this one:
link

Now there is no noise at all. An im able to dim from 0% to 100%.

Stil have the questions about the supply and the MeanWell LDD-1000.

Hope someone can share this info.

Tnx a lot for the help so far.

N

Wawa

The supply is regulated, but max voltage is 30volt.
That might not be enough to fully power three LEDs in series to 3*10watt (see post#7).

I don't know if the MeanWell is quiet. I think they are potted for that reason.

I make my own LED driver boards, and they buzz a little bit on certain dim settings.
Can't hear it anymore when the boards are inside an enclosure.
Leo..

Kumalix

ok, thanks for your info Leo.

One more question: How can you see on the datasheet dat it is a regulated supply?

N

Wawa

This is a swith-mode supply. They are all regulated.
"Load regulation 1%" is a hint. Unregulated supplies can vary more than 40%.
Leo..

Go Up