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Slow glow LED, how do I make one?

Discussion in 'LEDs and Optoelectronics' started by kila2000, Sep 27, 2012.

  1. kila2000

    kila2000

    12
    19
    Sep 27, 2012
    Hi
    Total new here, only just registered and I'm a total novice at circuit building. I know a little stuff but everything has been learnt from asking others.

    My question is, is there any way I can an LED start from off and slowly brighten to be fully on and then stay on? I have seen youtube vids of LEDs that slow glow and then slow fade using 555 timers and capacitors and such. What I have is 4 2v red LEDs wired in series to a 12v power supply with an 82ohm resistor in there. I would like to flick a switch and have the LEDs slowly brighten and then stay on til the switch is turned off again. Is this at all possible, and if so, could someone please talk me through how to make the circuit.

    Thanks for any help you can give
    Wil
     
  2. kila2000

    kila2000

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    Sep 27, 2012
    Wow, quick reply. Thanks for that.
    It looks to me like hes using a momentary switch, so if I was to use a spst on/off switch the LEDs would fade out until I turn it off, is that sound right?
     
  3. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    When you flip the switch on it would fade in and stay on until you flipped the switch off, than it would fade to black...
     
  4. kila2000

    kila2000

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    Sep 27, 2012
    Awesome. That would work for me. ummmm ..... he mentions a bigger capacitor means a slower fade in, if I use a bigger cap would I need to adjust the resistors?
     
  5. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    No, not necessarily... But, playing with the values of the resistors will have effects (as the author states) best thing to do is to build it and play with it... Resistors and caps are cheap, pick up a few different values of caps, and a resistor assortment and have fun playing...
     
  6. kila2000

    kila2000

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    19
    Sep 27, 2012
    Thats awesome, and so easy too. Thanks so much.

    I have another more complicated question, wondering if you could help.
    The LEDs I mentioned are a part of a model of Star Trek's Deep Space 9 I have been building and lighting. I have 11 LED circuits running thru the station to light different section via 11 individual switches but also with a master override that turns on everything all at once using diodes to bypass the 11 other switches.
    What I would LOVE to also have is a 13th switch that would also bypass the first 11 and light the whole station but in a timed sequence, starting with the fading in of the red LEDs. My limited knowledge makes me think 555 chips could be used for the timing but I really have no idea how I could even start to build such a circuit. If I can get that sorted it would be the last piece of the puzzle for this model. Any ideas?
     
  7. wingnut

    wingnut

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    Aug 9, 2012
  8. kila2000

    kila2000

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    19
    Sep 27, 2012
    Wow, another awesome reply. it looks like thats what I need. Looks like I have some things to play around with this weekend
     
  9. kila2000

    kila2000

    12
    19
    Sep 27, 2012
  10. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    Use a 4015 instead of the 4017 and don't do the step back progression... It will keep each step of the ladder 'on' until a reset...

    The 4017 goes like this...

    1000
    0100
    0010
    0001
    etc.

    A 4015 will go like this...

    1000
    1100
    1110
    1111
    etc.


    Here is an example, you can substitute a 555 timer in place of the 4093 clock circuit, or build it as is... You will need to implement the fade circuit for each LED as well...

    http://www.doctronics.co.uk/4015.htm
     
  11. kila2000

    kila2000

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    19
    Sep 27, 2012
    ummmm .... I'm confused with what you said. I appreciate the help but I don't really understand the terminology or the finer workings of electronics. I'f I'm told how something works and how to build it I'm fine. Looking at the circuits you linked me too I'm totally lost. I can see the 4093 clock circuit you say I can replace but the 555 has less legs right? so how would I hook it up? Also, where would I put in a switch? And lastly, if I manage to build a circuit like this, what would I do to change the timing between each LED coming on?
     
  12. CocaCola

    CocaCola

    3,635
    4
    Apr 7, 2012
    I'm really short on time to actually do a schematic for you as I'm packing for a trip to FL (also still lacking my main development computer as I await the hard drive parts)... Hopefully someone else can help you put all the ideas together and show you a schematic or I will try and help as time permits... Yes the 555 has less pins you would remove the entire 4093 clock and replace it with a similar 555 clock, the output is the only shared part that matters... There is nothing wrong with using the 4093 as documented in that link, it's just not me preferred choice you are not easily going to be able to adjust the 4093 timing like you can with a 555...
     
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