Thunderstorm Lightning LED - Page 1
Forum section: electronics / beginners

author: hgg
author_rank: Frequent Contributor
timestamp: December 10, 2013, 05:40:05 pm
content: Hi guys,Can anybody think of a simple way to make an LED light up like a thunderstorm Lightning?(simulating the flashing pattern and not the actual intensity of course...)Since lightning its an electrical phenomenon and everything has a fractal nature, meaning thatit can be scaled up or down, maybe similar discharge patterns can be produced with lower voltages.(No micro-controllers or Arduino simulations, just discrete parts.)Thanks!

author: SeanB
author_rank: Super Contributor
timestamp: December 10, 2013, 07:04:08 pm
content: Gated noise source that drives the LED with flicker noise. Or you use an opamp with a high level of popcorn noise ( cheap and nasty is better) with high gain to amplify it's own noise and drive the LED with the peaks.

author: hgg
author_rank: Frequent Contributor
timestamp: December 10, 2013, 07:31:29 pm
content: Hello SeanB,This sounds like a random noise signal with a fixed peak level. Lightning has many low intensityflashes with some strong intensity ones. Can you have random peak levels as well?

author: minime72706
author_rank: Frequent Contributor
timestamp: December 10, 2013, 07:34:59 pm
content: I guess rather than relying on the noise of the amplifier itself, you could use one of the well-known noise-generating circuits (I vaguely remember one involving 2-3 BJTs) and tune the gain of the amplifier such that it only saturates SOMETIMES. You'd tune it to the noise source you build.I'm also talking out of my ass - just throwing my thoughts out there in case they're helpful. I'd be very glad if someone called my idea stupid and explains why.

author: SeanB
author_rank: Super Contributor
timestamp: December 10, 2013, 07:45:04 pm
content: Peaks are analogue, so you will get bright and bim flashes that turn on the LED. Otherwise a PRNG with a clock where the pulse width is driving the LED via a RC circuit that means current is proportional to the high time. That just needs a shift register, an Xor gate and uses the other gated in the Xor as the oscillator.

author: hgg
author_rank: Frequent Contributor
timestamp: December 10, 2013, 08:30:04 pm
content: minime72706do you have any schematic of the noise circuit?SeanB, is that the noise you are talking about?http://en.wikipedia.org/wiki/Burst_noise,because this type of noise has a random timing but an almost constant peak.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 10, 2013, 10:53:22 pm
content: Quote from: hgg on December 10, 2013, 08:30:04 pmboth of these are decent examples, though you'd have to condition the noise to get the effect you want.It may be worth it to use a pseudorandom number generator (LFSR, for example) that has its (digital) output modulated by some other signal that makes the intensity look more random. You might also get a desirable effect by short-term averaging the LFSR signal. Although the LFSR signal looks random over a long time period, the density of 1's versus 0's is going to vary widely if you only look at a few periods at a time.Again, I'm just talking out of my ass since I haven't tried to do this sort of thing myself. It's probably worth playing with that noise circuit, however.Oh I just thought of another idea. Use a noise source and have one or more comparators looking for peaks in the noise signal above some preset threshold. If you use more than one comparator, you could have different peak amplitudes trigger flashes with differing intensity and/or width (time). This idea would also work with some PRNG with short-term averaging, as long as the clock to the generator is fast enough. (if it's too slow, the signal might look overly smooth rather than 'peaky')

author: Psi
author_rank: Super Contributor
timestamp: December 11, 2013, 12:04:22 am
content: Find a video on youtube of lightning, download it and crop/pixel resize it down so you get some averaging.Then watch it in slowmo and see what the pixel intensity actually does over the period of the strike.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 11, 2013, 12:05:31 am
content: Quote from: Psi on December 11, 2013, 12:04:22 amThat's not a terrible idea: you'll want a video that's already in slow motion, though.

author: Psi
author_rank: Super Contributor
timestamp: December 11, 2013, 12:10:40 am
content: ideally yeah, if he can find one.It depends if he just wants to reproduce the "look" of a strike, in which case he only needs enough detail that the human eye can pickup.Remember that when you see a strike in the sky and it seems to "travel along" that is really multiple strikes adding to each other.

author: hgg
author_rank: Frequent Contributor
timestamp: December 11, 2013, 04:21:33 am
content: minime72706 and SeanB thank you for your suggestions, I will try them out.Psi I want to reproduce the total amount of lightning that for example shines in your housefrom your window. So, its actually a pattern with several light intensities produced from themany short and long interconnected arcs.I don't want to simulate the produced light by analysing the phenomenon. I was rather lookingfor a property of any electronics component or simple circuit that its output behaves in a similarway.Maybe some kind of static discharge will have a similar behaviour.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 11, 2013, 04:29:00 am
content: I think a lot of what gives lightning its unique pattern is the variability in the atmosphere as well as the earth. The electrons (or holes, actually) find their own path of least resistance and split off seemingly at random.I think flicker noise might be a good start.

author: Psi
author_rank: Super Contributor
timestamp: December 11, 2013, 04:46:36 am
content: I don't think you'll find a low voltage similarity, lightning is still not completely understood.Lightning arcs travel much future than they should when compared to other high voltage sources.