>>You need about 1000 uF provides ~~ 1V of voltage "droop" per mA per=20 >>second. So, given a 20Hz low end and a 1:10 duty cycle the longest pulse would be=20 5ms. Assuming the LEDs draw about 50ma then 1000uF would droop .25 volts for eac= h=20 pulse. 1000uF might be a bit large (or might not). -- Bob Ammerman RAm Systems --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .