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Make LED glow slowly?

If you take a look at old Ibook G4 there is a stand-by LED that kind of glows slowly, I wonder what do i have to do to archive it, it would be perfect if it wound go dark completely yet would simply change brightness between say 70 and 100% so should i change voltage accordingly or? if yes then How? and wouldn't it be bad for the LED itself and for the battery, it is also important to mention that i'm going to use one or two AA batteries as a source. please help.

frollard8 years ago
a microcontroller could be programmed to use Pulse Width Modulation to make the brightness vary. Simpler would be to use a 555 to create a digital on-off to cycle the glows, then hook up the led thru a large capacitor. The led would light, slowly, (as the cap charged), then when the 555 output low, the led would run from the capacitor and get dimmer, then the 555 goes high, charging again.
mellink7 years ago
Just wondering if you wanted to make the LED glow on say when turned on. Could you just hook up a capatictor and then when the power comes on the cap will slowing let the LEd power up. Would that be possible with out the wineing noises? How do you calcuate what cap to use?