Caustic Photon Render Pass Posted November 29, 2009 Report Share Posted November 29, 2009 Hi! First post here! Loving the clean interface of this forum. Great people, keep up the good work! I am thinking of using a 74HC595 as described in the LED rings schematic: 11 LEDs per ring with column drivers, and X number of rings with row current sinks. 1. I believe each pin is sinking too much current. The Fairchild 74HC595 datasheet says 25mA sink or source under Absolute Maximum, MM74HC595 says +-35mA. Given that every 11th LED is on at once, or only 11 LEDs are on at once, this may not be a problem. But it seems like it is awefully close to the Absolute (read danger) rating. 2. It would be cool to apply a PWM signal the Output Enable (pin 13) of the 74HC595 to globally adjust brightness of the LEDs. This should work, right? Thanks again! CausticPhoton Quote Link to comment Share on other sites More sharing options...
TK. Posted November 30, 2009 Report Share Posted November 30, 2009 Hi, welcome to the forum! :) These topics are (partly) discussed in following threads: 1) 2) Addendum to 2) so long all LED rings should be dimmned from the same PWM signal, it will work. This is a simple programming example (for MIOS32) which demonstrates how to generate the PWM from a single timer IRQ: http://svnmios.midibox.org/listing.php?repname=svn.mios32&path=%2Ftrunk%2Fapps%2Ftutorials%2F007_mios32_timer%2F there is another (somewhere...) which demonstrates how to generate independent PWM waveforms by using modulo operations (not recommented for PIC) Best Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
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