Drive an LED with an emitter...?...[according to a resistance drop.

Started by petemoore, February 22, 2011, 06:48:39 PM

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petemoore

  100k pot biasing the base, strung across +/-.
  Emitter followers collector+, emitter>10k to -, Led across the 10k.
  I want an inverted lighting of the LED...shoulda started with an Opamp I suppose.
  OR some kind of:
  LED lighting when R goes low on an LDR.
  I was just messing with all bias points on the base and emitter follower isn't driving the LED [blipped lit a couple times for some reason].
  Everything still seems good including the freshly tested LED.
Convention creates following, following creates convention.

petemoore

  Sorry for confuscion, I'll google 'light LED' and see where that goes.
 With transistor gets me here:
 
 http://www.exo.net/~pauld/activities/electronic/transistor.htm

 I'll try inverting the LED...put current through it via emitter this time.
  Mod: I can work with this ! Had to turn the LED around, not used to LED in heavy current zone like emitter, thought I'd put a second R channel to ground  there for some reason, shy of current I guess.
 
Convention creates following, following creates convention.

Earthscum

can't remember how well it worked, but it's an easily tweakable design... I took the output off the LED (on this case, it was the anode, since cathode was grounded). That went across DC coupled to a fet. I dropped a 4.7k from drain to V+, and used a 10k pot on the source to bias it. Then I just dropped the LED from drain to ground. Worked pretty good with the MPF102. I haven't tried it with any other fets yet, but I'm glad I got to thinking about it and remembered. I came up with it when I was playing with the Tiny Trem.
Give a man Fuzz, and he'll jam for a day... teach a man how to make a Fuzz and he'll never jam again!

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petemoore

  A little more complex than 2+2 Vs. 2x2...one of those things...probably even knew that once, just was overthinking all around it.
Convention creates following, following creates convention.