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20 years ago I took electronics in school. Did very well, but never used it much since so I have forgotten just about all of it.

I have been testing in LTspice and just cannot get anywhere with this. Spent about 12 hours total before searching google. Found this wonderful site and searched and browsed for hours and tried a few ideas I found but nothing worked.

Here is the needed setup

  • 3 LED's per side of the vehicle
  • Using a simple on/off micro switch will turn on/off the running lights which consist of 2 of the 3 LED's per side
  • A 555 timer circuit (I have this part figured out) for the flashing (turn signals and hazards)

schematic

simulate this circuit – Schematic created using CircuitLab

  • A 4 position switch to now control the states of the LED's.
    • 1st position: nothing.
    • 2nd position: flash all 3 LED's on left side.
    • 3rd position: flash all 3 LED's on right side.
    • 4th position: flash all 6 LED's.

I have tried using NPN's in all sorts of configurations. DT switches to control where power goes... I am now at a loss, brain has run out of ideas. If we had SMD LED's with dual SAME color, this would be easy.

If there is any part someone doesnt understand, I can try to explain further.

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1 Answer 1

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schematic

simulate this circuit – Schematic created using CircuitLab

Diodes can be 1N4148 Resistors X control brightness of flash Resistors Y control brightness of running lights

Get rid of that 1uF cap on the output of the timer IC in your schematic (or connect it to the control pin), or it will do evil things.

The running lights will make D1, D2, D4, D5 a bit brighter during the flash, if that's objectionable, you can fix it by splitting the Y resistors into X and (Y-X)) and connecting the flash steering diodes to those junctions.

schematic

simulate this circuit

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  • \$\begingroup\$ This looks like it would definitely work. It's not as small as possible (i would have used some 74-series IC's) but it is simple enough. \$\endgroup\$
    – Wyatt Ward
    Commented Feb 1, 2014 at 21:36
  • \$\begingroup\$ Yes, @Wyatt8740 since he's looking at transistors I thought 4000 series CMOS (9V operation) would be a bit much. If it was for a paid project, I would have done it with a few lines of code and a micro. \$\endgroup\$ Commented Feb 1, 2014 at 21:40
  • \$\begingroup\$ I was so close to this a few times. I missed the placement of the running lights switch. I had near exactly what you gave and now when I saw the placement, it all worked. I did change to the split resistors to keep brightness even. It has been one of those "DOH" days. \$\endgroup\$
    – Mtgtnt
    Commented Feb 1, 2014 at 23:23
  • \$\begingroup\$ Glad it works for you! The steering diodes are really doing an kind of analog "OR" function. \$\endgroup\$ Commented Feb 2, 2014 at 0:02

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