Sigma-delta or Led Channel (PWM)? Which is better?

JoaoLopesF
Posts: 59
Joined: Thu Aug 17, 2017 5:40 pm

Sigma-delta or Led Channel (PWM)? Which is better?

Postby JoaoLopesF » Fri May 18, 2018 8:23 pm

I'm working on a project. This have 8 channels (Sigma-Delta ou LedC) of ESP32 connected to leds.

Frequencies of blink can vary from 0.2 to 50 Hz (ussually 0.5 to 20 Hz).

I did work with both types (by #define):

- With sigma-delta
- With Led channel

Technically sigma-delta is better than PWM (LedC), is this correct?

Questions from a beginner in sigma-delta?
- Is the capacitor needed to plug leds ?
f you add a capacitor between the output pin and ground, the average output voltage will be Vdc = VDDIO / 256 * duty + VDDIO/2, where VDDIO is the power supply voltage.
- Why the range recommended is:
recommended range is -90 ~ 90

Last edited by JoaoLopesF on Mon May 28, 2018 9:00 pm, edited 1 time in total.

Archibald
Posts: 107
Joined: Mon Mar 05, 2018 12:44 am

Re: Sigma-delta or Led Channel (PWM)? Which is better?

Postby Archibald » Sun May 20, 2018 1:03 am

As far as I'm aware, LEDC can flash an LED only down to 1 Hz.

It sounds like you need to drive the outputs directly from code especially if you wish to drive the 8 outputs in a sequence.

Beware of photosensitive epilepsy (link).

Regarding . . . .
If you add a capacitor between the output pin and ground, the average output voltage will be Vdc = VDDIO / 256 * duty + VDDIO/2, where VDDIO is the power supply voltage.
. . . . in my view it is inadvisable to connect a capacitor between output pin and ground without a series resistor.

JoaoLopesF
Posts: 59
Joined: Thu Aug 17, 2017 5:40 pm

Re: Sigma-delta or Led Channel (PWM)? Which is better?

Postby JoaoLopesF » Tue May 22, 2018 2:35 pm

Archibald,
Beware of photosensitive epilepsy (link).
I knew this, your advice is true for avoid problems with epileptics
in my view it is inadvisable to connect a capacitor between output pin and ground without a series resistor
This is true to me too

Thanks for your response

Deouss
Posts: 408
Joined: Tue Mar 20, 2018 11:36 am

Re: Sigma-delta or Led Channel (PWM)? Which is better?

Postby Deouss » Tue May 22, 2018 3:25 pm

Or use Remote Control feature.
It has 8 channels exactly as you need and allows smaller frequencies too
I think that would be perfect solution here

JoaoLopesF
Posts: 59
Joined: Thu Aug 17, 2017 5:40 pm

Re: Sigma-delta or Led Channel (PWM)? Which is better?

Postby JoaoLopesF » Mon May 28, 2018 8:59 pm

Hi, Deouss, tanks for response
Deouss wrote:Or use Remote Control feature.
It has 8 channels exactly as you need and allows smaller frequencies too
I think that would be perfect solution here
How use Remote Control feature (RMT) to control brightness of leds ?

Deouss
Posts: 408
Joined: Tue Mar 20, 2018 11:36 am

Re: Sigma-delta or Led Channel (PWM)? Which is better?

Postby Deouss » Tue May 29, 2018 1:30 am

Look at the rmt example included with esp-idf. All you need is to set up the transmission channel and control the transmitted waveform that you amplify to your leds.

JoaoLopesF
Posts: 59
Joined: Thu Aug 17, 2017 5:40 pm

Re: Sigma-delta or Led Channel (PWM)? Which is better?

Postby JoaoLopesF » Tue May 29, 2018 9:36 pm

Hi Deouss , I do this, thanks a lot

I see that top Arduino libraries for Leds, as FastLed, using RMT in Esp32, why not Sigma or Led Channel ?

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