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Originally Posted by Tokei
I think they based that on the IEEE 1789 standard. "Even frequencies in the range of 100–400 Hz can have a negative influence on the human organism, as is explained in IEEE 1789"
I could find that standard, but I didn't see the 100-400hz anywhere in the document (though admittedly I didn't read the whole thing). The paper is a meta-study, drawing a low-risk / no-effect curve from collating various studies on the topic.
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That's sort of what I meant. They gave examples up to 200Hz, but nothing for the 400Hz. If I was writing these sort of standards I'd pick the worst results than add a clear buffer.
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In their conclusions they actually use PWM as an example on page 46: "[...] the recommended practice for PWM dimming at 100% modulation depth is that the frequency satisfies f > 1.25 kHz. [...] This level of flicker could help minimize the visual distractions such as the phantom array effects. The recommended NOEL for PWM dimming is 3 kHz [...]." NOEL = "no observable effect level".
The paper itself is behind a paywall but the US Dep. of Energy has a nice summary here: https://www.energy.gov/sites/prod/fi...htfair2015.pdf
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That's an interesting summary. But, it just confirms to me that the 1KHz that the Forma uses is not going to be an issue.