NeoPixel refresh rate

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jiazhangwang
 
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NeoPixel refresh rate

Post by jiazhangwang »

Hi,

I have a question about the refresh rate of ‘NeoPixel Ring - 16 x 5050’ and 'Pixie - 3W Chainable Smart LED Pixel' .
In our project, I used Arduino to control LED, set LEDs to be light one by one at 60Hz and loop. I used a 60Hz camera to capture sequential images. But I found that LEDs didn't operate at 60Hz strictly. Sometimes they will miss a pattern, sometimes the LED is not fully bright , for example, it's 30% bright in the first frame, then fully light in next frame. So is that because there is slightly time delay between each of them, then it adds up to cause bigger delay. Thanks!

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adafruit_support_bill
 
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Re: NeoPixel refresh rate

Post by adafruit_support_bill »

But I found that LEDs didn't operate at 60Hz strictly.
Correct. Neopixels refresh via PWM and each driver chip is independent. So with a fast shutter, some pixels may appear brighter since they are at a different phase of their PWM cycle.

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jiazhangwang
 
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Re: NeoPixel refresh rate

Post by jiazhangwang »

adafruit_support_bill wrote:
But I found that LEDs didn't operate at 60Hz strictly.
Correct. Neopixels refresh via PWM and each driver chip is independent. So with a fast shutter, some pixels may appear brighter since they are at a different phase of their PWM cycle.
Thank you for the information. I am new to PWM things. I just checked that PWM fall time and rise time, which means that even we just operate one single LED, there will be a little delay(120 us) after each cycle, then it may have full jump after a certain time, is that correct?

And if we operate the whole ring, since all LEDs are chained together, there is some data transmission delay between LEDs, so it may cause some larger delay after a certain time, is that correct? Thanks!

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adafruit_support_bill
 
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Re: NeoPixel refresh rate

Post by adafruit_support_bill »

Each pixel has its own independent internal clock. So in addition to the communication latency from one pixel to the next, their PWM refresh rates are not synchronized.

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