# Roughly calculating lumens from PWM

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YuvalS
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Roughly calculating lumens from PWM

Hi all, couldn't find answer for this on the forum for my OL contest build.

Is there a table for the lumens output of 8*AMCs according to the PWM "on" percentage?
for example, pwm=255 is ~1000Lm, how many lumens are pwm=100 or what pwm value do I need to get 500Lm?
I know it is not accurate and depends on many other variables but I only need estimation, I don't care if I get 500Lm or 450 (or 550)

Thanks

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EasyB
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The output is usually close to linear with the PWM. Except for when the duty cycle is very low then you get additional effects from the slow turn on of the 7135 I think.

I just tested the output of my 8×7135 single XPL light with PWM values of 255(100%), 127(50%), and 46(18%), and the relative output by ceiling bounce was 100%, 47%, and 16%.

YuvalS
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EasyB wrote:
The output is usually close to linear with the PWM. Except for when the duty cycle is very low then you get additional effects from the slow turn on of the 7135 I think. I just tested the output of my 8x7135 single XPL light with PWM values of 255(100%), 127(50%), and 46(18%), and the relative output by ceiling bounce was 100%, 47%, and 16%.

Thanks, I didnt expect linear result since the Current-Lumen table is not linear but maybe it is logical since PWM is always maximum current.

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wle
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if 255 pwms = 1000 lumens then probably 100 would be

1000 × 100/255 = about 392

it would be mostly linear because current would still be peak current, only now it is on 100/255 of the time

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Lightbringer
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YuvalS wrote:
Thanks, I didnt expect linear result since the Current-Lumen table is not linear but maybe it is logical since PWM is always maximum current.

That’s exactly it. 1A constant current will be slightly more efficient than 2A at 50% PWM. So PWMing it will be more or less linear.

09 F9 11 02 9D 74 E3 5B D8 41 56 C5 63 56 88 C0