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Old 12-27-2012, 11:07 PM   #23
sysKin
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sysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the endsysKin knows the complete value of PI to the end
 
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Posts: 56
Karma: 31286
Join Date: Oct 2012
Location: Australia
Device: Aura HD, after a train ate my Glo
Quote:
Originally Posted by murg View Post
I'm getting the feeling that the Glo uses software PWM.
If true, this should ruin battery consumption, because the CPU would have to be continuously running.

Quote:
Originally Posted by TechniSol View Post
properly filtered or smoothed with an RC filter
Filtering is not nearly as easy as you make it sound. Firstly, LEDs are current-controlled not voltage-controlled, so you want to smoothen current, not voltage. This immediately points to an inductor rather than capacitor, and inductors are big and expensive. Secondly, you don't want to dump the unwanted energy (the high frequency components) to a resistor, it's an immediate waste of precious battery power (as soon as you include any resistor anywhere, it might very well defeat the purpose of PWM).

I'm not saying it's all not solvable (with some compromise between cost and power waste) but in the end, I don't think I've ever seen a PWM/switchmode LED controller that would have any filtering. They usually just use frequency that's high enough instead...

Quote:
Originally Posted by KevinShort View Post
ioctl(light, 241, brightness);
Curious about the 241 magic number. Can it be that another number controls the frequency?
I'll have to figure out if I can cross-compile on Windows too...

[edit later] BTW, I don't see any flickering at light level 1 - maybe it's too bright outside to see it... it's just like level 2 (GUI minimum) only a little bit darker.

Last edited by sysKin; 12-28-2012 at 12:23 AM.
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