Blinking Light Design

Discussion in 'The Projects Forum' started by Helena123, Apr 15, 2014.

  1. Helena123

    Thread Starter New Member

    Apr 15, 2014
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    So I'm trying to design a randomly blinking light chain and have found a few designs online. My two main sources are:

    http://www.nutsvolts.com/uploads/magazine_downloads/NeonLamp-Information.pdf

    (page 4)
    and

    http://www.instructables.com/id/Blinking-LED-Mood-lighting/?ALLSTEPS

    However, I had some questions. My main one is, what is the purpose of the capacitors in the first design? My take on it is that it increases randomness regarding the blinking, but can someone explain/prove why or why not that is correct? Would the first design work without the capacitors?

    Also, does the spacing matter for each of the designs; the second one mentions spacing but the first one doesn't seem to other than an approximate visual. I know the current will travel the path of least resistance, hence the resistors being the same value, but would the current have a more difficult time reaching the end of the circuit, thereby favoring the resistors/diodes near to the source V?

    Thank you!
     
  2. #12

    Expert

    Nov 30, 2010
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    In the first circuit, the caps are all time constants. "wait this long, then fire the bulb", and, "wait this long then fire the other bulb".

    The second one doesn't have a schematic that I can see, but, "path of least resistance" is a distorted view. Current takes every available path in inverse proportion to the resistance in each path. The only differences cause by spacing are in the range of milliohms and nanoseconds, and YOU can't see either of them with your eyes.
     
  3. inwo

    Well-Known Member

    Nov 7, 2013
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    The first only works with neon lamps.

    Can't get any simpler than the second design.

    Should work fine unless you need to control the timing.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    The Cu tape is available at stores that sell stained glass supplies, or " circuit-stik " from some electronic supply stores like Elliot in Tucson.
     
  5. Helena123

    Thread Starter New Member

    Apr 15, 2014
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    Thanks, but would the 1st one theoretically work if the capacitors were not present?
     
  6. inwo

    Well-Known Member

    Nov 7, 2013
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    See post #2. :confused:

    Lights would be all on.
     
  7. #12

    Expert

    Nov 30, 2010
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    What he said ^

    Without the capacitors, there is no, "wait". All the lights would come on immediately and stay on continuously.
     
  8. Helena123

    Thread Starter New Member

    Apr 15, 2014
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    I mean in more an equation format- more the theoretical functionality of the circuit. With each capacitor having the same value, would they not have the same equation, where would the difference actually come from?

    If that is the case, how does the second one operate?
     
    Last edited: Apr 16, 2014
  9. inwo

    Well-Known Member

    Nov 7, 2013
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    The first one uses different RC components for each circuit.

    Although even if they were the same, small differences would still allow lamps to get out of step and look somewhat random.

    Just like the second example. Even though all the blinking leds use the same internal electronics to blink, they soon get out of step.

    As was explained in the link.

    If you need explanation of how RC relates to timing, I'll defer to others. I'm not qualified.
     
  10. Helena123

    Thread Starter New Member

    Apr 15, 2014
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    I'm really looking for the exact timing differences explained if possible because that's a central area of confusion :confused:
     
  11. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Is this a real project that you plan to build or a homework assignment?
     
  12. Helena123

    Thread Starter New Member

    Apr 15, 2014
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    Honestly it's a gift for my girlfriend; I just really don't understand some things about it and I feel like I should so it's bothering me. It seemed simple enough that I can figure it out but it's seriously bothering me now and no stores around me seem to have the copper metal foil tape the second design calls for.
     
  13. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    Okay, then you should probably focus on the LED design. The voltage required for the neon lamps is difficult to source in a compact package. What exactly, would you like the lights to do...just blink on and off, or follow some sort of a pattern? What physical size do you have in mind? Do you want it to be battery powered, and if so, how long do you expect the batteries to last?

    There are lots of people here who can and will help, but rather than deal with a lot of questions about a 40 year old neon lamp circuit, let's start with the objective you are trying for, and move on from there.

    The metal foil tape is not required; it's just what that particular person used. Wires are better in lots of ways.
     
  14. Helena123

    Thread Starter New Member

    Apr 15, 2014
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    Frankly I'm going exactly for what the second design is doing, blinking on and off randomly, I've considered just wires but I also want to keep things aesthetically pleasing ... honestly, something smaller would be best.
     
  15. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    The instructable project uses LEDs that have built-in blinking circuits. Thus, all that is required is to:

    select the specific LED you want to use,
    decide how many LEDs you want,
    decide what voltage you want the whole thing to run on.

    Then, it will be possible to select a resistor value to limit the current to each LED.

    Then, it will be possible to draw a schematic.

    Then, you can start building.
     
  16. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    For a LED panel, I have used 1/8 in cork sheet attached with contact cement to tin plate, or thin aluminum. LED's were spaced 9/16 with 2 resistors for ea bi-color LED. Stretched # 22 tin plated Cu wire makes nice clean buss lines, attached every few in with your favorite adhesive like hot glue gun.
     
  17. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    Define smaller? :cool: The Instructables author chose 2", but it is somewhat a random choice. As long as you have enough space to solder to the LED leads and include the resistor, you could make the spacing as small as you want. If a little extra thickness is acceptable, the resistors can be mounted vertically to get the LEDs closer. Or you could use SMD resistors to save space as well. And how many LEDs you want also affect the size. He used (as I remember) an array of 6 x 8 LEDs. You could decide that an array of 4 x 4 LEDs are sufficient. With a smaller spacing around the edge and 1" between LEDs, you could get this down to a 4" x 4" square. Similar adjustments will result in almost any size you want. :rolleyes: You aren't restricted to a square or rectangle either. The same idea can be used to make a heart or other figure.

    You want it asthetically pleasing? :confused: Make a cover for the bottom. Consider plexiglass or foam core board (depending on how much grief it will get). Or 1/4" plywood (it could replace the foam core, too. And flat trim molding for the sides (available at Home Depot or Lowes)

    Sorry for the brain dump, but I thought I'd present as many options that I could think of, to expand how you are thinking about your project.
     
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