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Help iwth circuit

  1. Dec 5, 2004 #1
    this project is for my bike indicators in the rear with 6 led's
    it needs to make 2 sequences as they light up controlled witha switch
    here are the sequences
    what i am tring to do is have a sequnce LED flash rather then just on and off... here is what i want
    then back to
    and when mode pin is connected to Pin 4 V+ on LM3914
    it should have a different sequence like this
    and i will add a small switch on the project box i place the circuit in. and the box will be placed in my trunk i can change it periodicaly if i want to.. or have the switch in another place in the front but not sure yet.
    Now my circuit is done but i don;t know if it will work..
    can you check it out see if you think it might not work?
    flasher wire is the wire thats in the rear right now it provides a pluse from factory flasher. so i used transistors as switches....
    some one else made this circut for me so i really don't know the values of the resistors and everything
    http://www.electro-tech-online.com/files/lm3914_sequencer_107_105.jpg [Broken]
    Last edited by a moderator: May 1, 2017
  2. jcsd
  3. Dec 5, 2004 #2


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    Didn't take alot of time to look it over but the one thing I noticed is that the PNP transistor that has its base hooked to the NPN transistor will most likely have the base emitter juction reverse biased to 12 volts at one time or another. A 3906 will not tolerate a reverse voltage this high on the base emitter junction. I think it's around 6 volts. This is not an uncommon design error. Although some circuits are configured so the base emmiter junction is NEVER reverse biased, those that are often time get overvoltaged.
  4. Dec 5, 2004 #3
    Just a thought; maybe I'm missing something but...

    Why not simplify the input signal circuit with the flasher output feeding through an adjustable resistor to a capacitor, connected to input pin 5? The resistor can be set to give a full scan within the flasher cycle. A second resistor to ground can bleed it to 0 quickly between flashes.
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