LED "breather" needed

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LED "breather" needed

Post by neeb » Wed Apr 24, 2002 4:47 pm

if anyone has seen an IMAC in sleep mode, you may have noticed the power light illuminates and dims as if the light were breathing. if anyone can direct me on how to make such a circuit, i would be psyched. would a slow sine wave with a diode to cut negative values be a good idea?
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Re: LED "breather" needed

Post by russlk » Wed Apr 24, 2002 8:30 pm

A triangle wave is easier to make. Start with a square wave oscillator, follow with an RC filter and a transistor emitter follower or JFET source follower to drive the LED. I will try to post a schematic at www.geocities.com/russlk/blnkled.gif
You will need to copy and paste the URL into the address bar or Geocities will not open the page.<p>[ April 24, 2002: Message edited by: Russ Kincaid ]</p>

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Chris Smith
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Re: LED "breather" needed

Post by Chris Smith » Wed Apr 24, 2002 9:42 pm

Its called a "staircase" generator. The wave form looks like a series of steps going up and then returning down. Its a step wave simulated sine wave like they use in Step wave AC invertors. You set the dwell on each little step to a given amount of time and one full cycle might contain thirty little steps going up, taking a total time of for example.... three seconds,.... or thirty seconds to complete one cycle, set by you.<p>[ April 24, 2002: Message edited by: Chris Smith ]</p>

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