LED Strober

Discussion in 'General Electronics Chat' started by Metalfan1185, Nov 9, 2008.

  1. Metalfan1185

    Thread Starter Active Member

    Sep 12, 2008
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    I am familiar with NE555 and other timers, im looking for a way to strobe LED segments like in this video, it seems that the red flashes on, then blinks, and then the blue flashes on, and then blinks...

    Im thinking it may require a 555 and a 7404 inverter, but how do i get them to blink?

    http://www.youtube.com/watch?v=DdHluHTpYv4

    Please Help! Im stuck big time
     
  2. Audioguru

    New Member

    Dec 20, 2007
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    The LEDs are probably run from a micro-controller.
    you can also do it with a pile of logic chips if you want.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    I agree with Audioguru.
    One small microcontroller IC driving some MOSFETs would be the way I'd approach that.

    Trying to do that using discrete logic ICs would be painful, expensive and time-consuming.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    How many pair of LEDs are you wanting to flash? Are they off the shelf, or high end units?

    If you want to duplicate the entire car I have to agree with what was said, and it will likely be expensive in any case (just cheaper and simpler with the microcontroller).
     
  5. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    If you really like 555's,heres a bunch of em, as for appearance of first flash being longer it will be true here;charging of .1μF timing caps ,on first flash starts from ground,sucessive charges start at 1/3 of supply. First 555 is set for about 3 sec.,other two 555's alternate at about 5 per sec.
    LED clusters based on All Electronics CAT# CLD-4x [x=R orB] @$6. ea,$ LED Cluster, 5-12V. chrome base. www.allelectronics.com. With 200ma drive you have many options.
     
  6. Metalfan1185

    Thread Starter Active Member

    Sep 12, 2008
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    Thanks guys

    I am building the enclosure for the LED's myself, the LED's are 2.3V a piece i think, so i can use them in series strings of 4 or 5 with the right resistance @ 12 - 13.8V. THe LED's im using are also rated for 70mA instead of the usual 20mA. they are pretty bright.

    I think i may print that circuit out and build it, and try it out. I think what you have there may be exactly what im looking for.

    I don't know how to use microcontrollers, i wish i did.

    Thanks again for your responses. Anything in regards to flashing the headlights? Could i use something similar? may be a timer and MOSFET.
     
  7. Metalfan1185

    Thread Starter Active Member

    Sep 12, 2008
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    The only thing im going to change on your circuit when i build it, is to add a MOSFET on the pin 3 outputs of the 555 pair. This will make sure that i don't overdraw too much current from the 555
     
  8. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    I'm going to dirty the waters a bit : To simplify ckt. use 2 556's instead of the 3 555 & 74C74. Change existing print before replacement as follows; interchange 1M & 1K on first 555, output will now be almost square wave [maybe a little to slow] ; replace 74C74 with 555,used as an inverter, pin 7 open, pins2 & 6 tied together connected to pin 3 of first 555. Pins 3 replace Q & NOTQ. On second 555 connect p. 4 & 8 to +,1 to ground bypass p.5
     
  9. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Using FET's , + side of LED's will go to battery +, drain to - FET, source to gnd. First two 555's ,with FET's should drive headlights just fine. Allow plenty of current capacity because cold filaments are thirsty; might add a little keep-alive current to the bulbs, just enough for a dull red.
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    If your LEDs are the square critters with four legs, they may be Superflux LumiLEDs by Phillips. For those, Vf(typical) is 2.6v @ 70mA.
     
  11. Bernard

    AAC Fanatic!

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    Just a few mods, using all 555's
     
  12. Metalfan1185

    Thread Starter Active Member

    Sep 12, 2008
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    yes, that they are. Nice LED's...one of my favorite to work with as far as automotive applications go.



    I don't have any fets, Can i use a Mosfet and switch it on the low side?
    I have tons of those
     
  13. Metalfan1185

    Thread Starter Active Member

    Sep 12, 2008
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    I ran a Sim with electronics workbench multisim 8, here's a copy of your schematic in file, not quite what im looking for, but closer. you have the right idea,

    short flash red...long flash red...short flash blue....long flash blue....repeat


    Thank you so much, maybe my sim is incorrect, run it if you can and maybe we can get this working...

    again, thank you for your time and skill. I can do logic, but i get confused with stuff like this lol
     
  14. Metalfan1185

    Thread Starter Active Member

    Sep 12, 2008
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    well, wont let me post project, and image is too big, this forum is kinda restricting! lol
     
  15. SgtWookie

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    Absolutely you can use MOSFETs.

    If you derate them considerably, you won't have to use heatsinks.
     
  16. SgtWookie

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    Well, most folks don't have Multisim. Try posting graphics of your results. .PNG format is preferred, as there is no distortion like with .jpg format files. .PDF format does work, but it requires a lot of resources on the other end to load. Try .PNG first.
     
  17. Wendy

    Moderator

    Mar 24, 2008
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  18. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Long blue short blue etc, give us some timeing and cycle rates and we'll see what can be done, whats a few more 555's.
     
  19. Metalfan1185

    Thread Starter Active Member

    Sep 12, 2008
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    Ok, so lets see, Here's a sequence id' like to figure out:

    Long Blue
    Blink Blue
    Blink Blue
    Long Red
    Blink Red
    Blink Red

    Entire red cycle : 1 second
    Entire blue cycle : 1 second


    Long pulse : about .5 sec
    Blink : Quick Flash


    Trying to emulate the same speed of Police Flashing lights, like on top of the police vehicles.
     
  20. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Thanks for yuor answers, I made this guess before ans. Turn dia. upside down and long pulse will be first. Long = 500 ms, flash =60 ms, off space between flashes =190 ms. How about 2 more flashes and less off time?
     
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