trigger LED

John Larkin · 2020-01-06T20:01:35+00:00

I'm doing a small box that accepts a user trigger. I'd like to flash an LED every time it gets triggered. Something like 100 ms, on a blue LED. The obvious circuit is a 74lvc1G123 one-shot, set to 100 ms pulse width. But how fast will that work? I'd like to go to 50 or maybe 100 MHz. Would it keep retriggering? I wouldn't want the LED to go out at high trigger rates. There is a specified "retrigger time", but I'm not sure what that means. Has anyone really over-triggered these things? I guess I could breadboard and try it, but asking is easier. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com

Jan 06, 2020 41 Replies

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George Herold 6 years ago

LED's keep getting better! Looking at the 'transfer ratio' of an led, electrons in to photons out, is kinda fun.

Led's I looked at years ago would start to 'crap out'* at a few mA.. I wonder if they are better these days.

George H.

*transfer ratio became non-linear... you needed to add three electrons to make two photons at low current/voltage.

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jlarkin 6 years ago

I got visible light from a green LED at 1 nA.

John Larkin Highland Technology, Inc The cork popped merrily, and Lord Peter rose to his feet. "Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"

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