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Led Current Calculation Issue

Hi,

In my project i need led flashes each 5 or 10 seconds.(It depends on calculations about current.) Each 5 or 10 seconds 100ms led flashes and it must flash for 5 years. Thats why i'asked you about consumption.

I'm in confusion about led's datasheet's. In datasheets led's peak forward current is approximately 100 mA and forward current is 15-20 mA. 

Firstlyi i'll write my steps, where i did wrong you see.

Assume that, each 10 seconds my led flashs for 100 ms and for 1 year.

1) In 1 year, there are 3.153.600 times 10 seconds

365x24=8760 hours

8760x60=525.600 minutes

525.600x60=31.536.000 seconds 

2)How many 10 seconds are there in a year ?

31.536.000/10=3.153.600 times 5 seconds been in a year.

3)I think, this is the part i made wrong calculation,

In datasheet, peak forward current is 100mA.(1/10ms Duty Cycle with PWM.) 

After that, led's forward current is 20mA.

That's why, i calculated 100mA for first peak and 20 mA so 100mA+20mA=120mA for hours. (I explained clearly, i hope)

And in 1 hour, there are 60 minutes and 60x60=3600 seconds and 3600x1000=3.600.000 milliseconds in one hour.

When i divide 120mA to 3.600.000 so, 120mA / 3.600.000=3,3x10^-5 or 0,33 uA.

4) When i multiply (3,3x10^-5) x 200=0,006mA or 6uA current consumption in each 200ms.

5)Finally, i found consumption each 200ms and i'll multiply with 31.536.000 seconds.

0,006mA x 31.536.000=210.240 mA.

That's my calculation. I'm not sure about results. Where did i wrong ? 

With warmest regards.