Advice on LED strobing?

Discussion in 'The Projects Forum' started by Tmesis, Dec 11, 2012.

  1. Tmesis

    Thread Starter New Member

    Dec 11, 2012
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    I'm assuming this is quite a trivial question for the majority of people, but I'm quite a newbie at electric circuits so a bit of advice would be really helpful.

    I've planned out a circuit which would allow a number of LEDs to strobe (at least I think) but the maximum frequency (it would be variable) of flashes comes to around about 68/70Hz, so my question is quite simply; is this even possible?

    I've done a lot of googling to try and find the answer, but every LED strobe light I find seems to be around the 10/12Hz rate, which makes me wonder if my plan is feasible.

    Cheers in advance,
    Andy
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
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    Assuming these are regular LEDs, or can, at least, be controlled the same way, yes, this is possible. However, the reason most strobes have such a low frequency is because human vision cannot see flashes that fast. We see roughly, and I mean roughly around 30Hz, much beyond that, the light appears to simply be 'on'. This is why you can watch tv, which, usually refreshes every 60Hz, unless you are a HD fanatic, then yours probably refreshes around 240Hz.

    In short, you can do it, but a large portion of your frequency capabilities will be useless for a strobe light...
     
  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I can see my 60hz 120V mains LED xmas lights flickering (but my wife can't).. Its annoying and makes me feel sick (or drunk which isn't so bad really :) ).
     
  4. tshuck

    Well-Known Member

    Oct 18, 2012
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    Yeah, that's possible, can you only see it when not looking directly at it, or can you see it when when in your focus?

    If it's when in focus, and I hope you don't mind me asking, are you colorblind, or have trouble distinguishing colors? This is not meant to be offensive, I promise, it is purely out of scientific inquiry. The rod cells in your eyes are sensitive to b&w and have a higher frequency response than the cones that allow you to see in color. So, it would stand to reason that a person with more rods could see that flicker...
     
  5. wayneh

    Expert

    Sep 9, 2010
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    It's a little odd your wife can't see it. I think women in general are a bit more sensitive to the flicker, or at least are more vocal about it. ;)
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I can only notice it when I'm looking directly at them and yes mostly when I'm scanning/moving with my eyes (think thats the intend of your focus question)..
    I don't see the flicker around in the room when I'm not looking at them. And when I try to look at 1 specifically I don't notice it as much as when I'm scanning over them/looking around in the area.

    No not color blind and have no trouble distinguishing colors.. In fact I can distinguish/identify shades of colors much better than many others I've noticed.

    I'm always in focus except for about 5-6 hours on Friday and Saturday nights.. Then I'm 8+ beers in and focus is not an option. :)
     
  7. ErnieM

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    Apr 24, 2011
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    I'm in mcgyvr's camp here, I am very sensitive to blinkie LEDs too. While I can't directly see 60 Hz flashes I am aware they are there. I know that is a poor description but it's all I have. Should I blink or even move my head some I do detect the flashes as persistence of vision leaves a hole as the light tracks across my retina.

    It borders on dangerous when I am driving as it draws my attention to tail lights that need no such attention. When I can scan the road my attention is subconsciously drawn to cars just traveling in front of me, as the flash is perceived as movement where none should be, and thus flashes a DANGER signal and I take double looks.

    Aside from near sightedness I have no other visual problems.
     
  8. tshuck

    Well-Known Member

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    This seems more like what I was describing with the rods. When you focus on something, it is primarily cones doing the work, while the peripheral is comprised of rods, which are sensitive to changes in light intensity and movement. So, while you can't see it when directly looking at it, you'd be able to get hints of it when you blink/move your head/focus on something nearby...
     
  9. wayneh

    Expert

    Sep 9, 2010
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    I agree that it causes a distraction when driving, because the movement of your eye creates what appears to your brain as multiple light sources. You don't see "trails" like you're on acid, you see individual flashes in your peripheral vision. I can't see it when looking directly at it, only when moving.

    I like the bright saturated color of LED holiday lighting but the flickering gives a mood that is, to me, the opposite of the warmth you want to enjoy. It might be fine for a disco but it feels cold and out of place on a tree or around the hearth. My outdoor lights are old-school C7 and C9! Don't tell Algore.
     
    Last edited: Dec 11, 2012
  10. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    So yes my rod is sensitive then ;)
     
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