LED fade in/ fade out

Discussion in 'The Projects Forum' started by ucitelot, Mar 21, 2011.

  1. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    i need schematic for led fade-in/fade-out for couple of minutes for
    20 LEDS 0.5W 150ma
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    Sorry, can't give you what you need.
    But it might help searching for PWM'ing LED's
     
  3. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    yes with NE555 byt dont know it will be with 20leds with 150ma
     
  4. Wendy

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    Mar 24, 2008
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  5. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    this one http://forum.allaboutcircuits.com/showpost.php?p=323548&postcount=132

    i see sequential fade, is that what i need
    -turn on, fade in (couple of minutes) and stay on 100%
    -turn off fade off (couple of minutes) and stay on 0%
    how much slowet fade in/out better

    the only thing it i want all leds can it be done couse they are
    20 extra bright 0.5W 150ma leds
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    That is the 3 step sequencer I mentioned. One LED fades in/fades out, a second different LED fades in/fades out, and then a 3rd LED fades in/fades out. That OP used 3 color LEDs. It was my Christmas vacation, so I had lots of time, so I used it to write a tutorial.

    It can be adapted to 150ma LED very easily by changing the resistors. The circuits I showed in Chapter 12 in figure 12.2 are basically very, very similar. MOSFET transistors are a joy to use for these applications. If the components are good quality they simply do not get hot.

    So, I was under the impression you want a simple fader, correct?

    How much do you know about LEDs?
     
  7. ucitelot

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    Mar 14, 2011
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  8. Wendy

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    You just adjust the "slow" oscillator to fit your needs. The schematic is there on Figure 12.2, unless you are wanting something different in special effects. This is probably a dumb question on my part, but are you wanting me to draw it for you? If so it will be almost a week, I work for a living and have a full life. I'll be glad to do it mind, it will just take a little while.

    At the end of the drawing process it will basically be the same schematic, with the values tweaked.

    BTW, what part of the world are you? The reason I ask is some parts are more common than others in various places.
     
    Last edited: Mar 21, 2011
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  9. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    afcours not, just asking for some working schematic what can work with those power leds, i will draw example D

    and see how its working, thanks a lot


    edit: im from europe (macedonian)
     
  10. brozizds

    Active Member

    Aug 15, 2010
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    ucitelot, Bill M. is quite the person to work with he has helped me with several projects and yours can be made with the same components I used as mentioned in the thread he posted and you can adjust the fadetime very easily JIM
     
  11. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    yes i see that, and will ask, (better to ask do not make mistake, or burn the leds)

    [​IMG]
    http://forum.allaboutcircuits.com/picture.php?albumid=45&pictureid=1129

    on example D will make
    what its U3b again 7555 or
    and is that IRF510 or (connected with R5 and leds and GND)
     
  12. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    i assumed U3b its LM393
    and make based on that, only to tell me is that IRF510, (so do not mistake GDS pins)
    and here is pcb design, so if can someone see it and tell me is it ok (dont wanna to make mistake)
    [​IMG]

    thanks a lot
     
  13. Wendy

    Moderator

    Mar 24, 2008
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    Looking at 12.2D I have some reservations. I need to rethink the driver for the MOSFET, I think I screwed the pouch on this one. You also left the U3a part of the schematic off, it is simple enough though, pins 1 - 4 are grounded.

    I looked at the earlier posts, maybe I missed it, but what is the power supply voltage?

    I also need to update the schematic in several other ways, you picked up on the 0.1µF caps (which is good). You also need a 100-220µF cap across the power supply.

    Liked the schematic, nicely done. If you don't mind I may use it in my article, which credit to you given.

    I'm thinking of adding another 7555 to use as a driver for the MOSFET. I could also use a couple of transistors, but the chip would be simpler.

    One second thought I'll used two BJTs, a NPN and PNP. I'll try to have it redrawn in a day.

    Part of the reason I do the tutorials is they teach me a thing or two. I've run some experiments since I drew those illustrations that tell me it won't work. After I draw yours I'll redraw those.
     
    Last edited: Mar 21, 2011
  14. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    ok great, upload the image here so will change the schematic, and post it to see it

    p.s power supply its 12V input and output 3.0-3.8 V 150 ma
    but may be output also 12V
     
  15. Wendy

    Moderator

    Mar 24, 2008
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    How many LEDs? And what color? You've stated 150ma for them. I've worked with 700ma LEDs, but never 150ma. I'll have to look up that link when I'm on my computer.

    I am assuming white LEDs, which drop around 3.4-3.6VDC. Different colors drop different voltages, which use different resistors because of it.
     
  16. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    yes white (extra bright) 0.5W leds
    ill put 20 of them
     
  17. Wendy

    Moderator

    Mar 24, 2008
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    OK, this is a preliminary schematic, it isn't quite finished, but it has most of the changes you need.

    [​IMG]

    What is left is I need to look at the LEDs.

    Q1 and Q2 are not critical. I would use 2N2222A (NPN) and 2N2907A (PNP) because that is what is available locally, but any decent switching transistor would work.
     
  18. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    thanks, only when you have time to put in one schematic, like now im little lost about u3a, u3b, lm393 and c4 c5 c6
     
  19. Wendy

    Moderator

    Mar 24, 2008
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    The LM393 is a dual comparator. It has two comparitors, we only need one. The chip U3 is the LM393. I mentioned in post # 13, first paragraph you left U3a off the PCB. One part of U3 is A, the second part is B.

    Are you using a google translator? The schematic explains C4-C6 in its text under the note, but if you are not reading English I can see how you would miss it. If this is the case (a google translator) I don't hold it against you, it is pretty common here. It says, "Note: C4, C5, and C6 are placed across the power supply pins of U1, U2, and U3.". The assumption is one capacitor per chip. They are to suppress switching noise from the oscillators and comparator.

    I'll let you read and digest what I've said, then respond, then we can continue where to go. Some experimentation with the LEDs on your part is coming up. How stable is your 12VDC power supply?
     
  20. ucitelot

    Thread Starter New Member

    Mar 14, 2011
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    yes for some words i use google translate, i dont know how didnt see that mention on #13
    will read all again and change the schematics
    one thing only
    VCC on 7555 on what pin its, is it pin 8, on 7555schematic dont know is it the same VDD

    and the power supply its from one old laptop i got 1.5a max90W 12V
    i guest its to stable since it was used for laptop
     
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