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strobes


spookybenz1
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I use xenon strobes in my display, but I also tried some of the LED strobes that Greg uses, and they seem to be of similar brightness.

 

I heard some concern that the LED strobes would not achieve the randomness that the xenon strobes do very quickly, so I drew a schematic of one to find a solution. The LED strobes use a 555 timer, which is much more stable than the SCR/neon light timer circuit used in xenon strobes. It should be possible to induce some randomness by "pre-charging" the LED strobes by turning the channel on at 10% or so for a few seconds. Based on my analysis of the circuit, this should not harm them.

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I have a couple of those LED strobes from Daryl also.  Yes - they're brighter than any other LED strobes I've seen - by far - but look for a lower flash rate.  I think he also has (or was talking of getting) a 1-2 per second model.  That would be my choice.  Unless you're ABSOLUTELY SURE you want something flashing as fast as 3-4 times per second.  That's awfully fast. 

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I've got some LED strobes...so I'll try that also, precharging. I never used them in a show because they all flashed at the same rate for several seconds which defeated the purpose.

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I have a couple of those LED strobes from Daryl also.  Yes - they're brighter than any other LED strobes I've seen - by far - but look for a lower flash rate.  I think he also has (or was talking of getting) a 1-2 per second model.  That would be my choice.  Unless you're ABSOLUTELY SURE you want something flashing as fast as 3-4 times per second.  That's awfully fast. 

George,  the 3-4 fps is a great rate when mixed in with the 1fps strobes.. together they actually look almost random.

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I use a couple hundred xenon strobes that I've collected from various vendors, so random really isn't an issue for me.  I was simply advising that those LED strobes from CLS are very fast.  (The fastest I've ever seen, actually.)  For those who like it - great - but that flash rate isn't for everyone.

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Well, I first bought 25 of the LED strobes for use in my first megatree but was sadly disappointed when I saw them all flashing together during initial testing on the floor. I went to xenon strobes for that tree and again for my second megatree which work real nice. I'll get the LED strobes back out and try the precharging idea and see if it improves things but even so, they aren't going on my megatrees...lol Possibly somewhere else so will see.

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Well, I first bought 25 of the LED strobes for use in my first megatree but was sadly disappointed when I saw them all flashing together during initial testing on the floor. I went to xenon strobes for that tree and again for my second megatree which work real nice. I'll get the LED strobes back out and try the precharging idea and see if it improves things but even so, they aren't going on my megatrees...lol Possibly somewhere else so will see.

Mix the LED and xenon on the same string,

Gives a very good random effect, this is what I did this past year, just put them in randomly

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I'll get them out and play with them some more on the floor. As I said, testing them two years ago, all blinking together for a good 5-10 seconds, just didn't cut it for me. Even if I mixed them into the megatree's xenon strobes, it would still show up...I think.

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Steven, can you actually get to the circuit where you could change the capacitor{s}-resistor{s} that control the flash rate to a different value to change the current flash rate?

 

I know that the 555 timer can be regulated for various flash rates using different values of resistor{s} and capacitor{s} from my playing around with them quite a few years back.     So if the circuit is easy enough to remove and change out the proper components, couldn't you set your own various flash rates on them to achieve the randomness effects one would want?

 

I've never seen or used an LED strobe, all mine are those screw in types you get at a Spirit Halloween store, just the standard lamp E-27 base types.  But the ones I have the PCB is sealed in an encapsulant and would be very difficult to exchange components on, just wondering if the LED strobes are also sealed with something that would make what I ask about above quite difficult or not even possible.

Edited by Orville
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My LED strobes are the same package...screw-in type and quite sealed up. It might cost more in time and trouble to attempt to modify them but hey, if time is there and they are gathering dust, money spent being wasted already..so it wouldn't hurt.

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Steven, can you actually get to the circuit where you could change the capacitor{s}-resistor{s} that control the flash rate to a different value to change the current flash rate?

 

Not easily. The only reason I got to the circuit is because one strobe was damaged in shipping (case was broken) so it was no longer suitable for outside use. The strobes are nicely sealed with caulking so this would have to be broken and re-applied after de-soldering and replacing the resistor. I wouldn't consider it worth it.

 

Here is my crudely-drawn schematic:

Strobe%20Schematic.png

The AC is passed through a capacitor which has an impedance of about 4kΩ when on 100%. When dimmed, there will be some harmonics which lower this impedance, but the result will still be under 200v across the 400v capacitor. The 18 LEDs in series have a voltage drop of about 65v, so the experiment is to determine at what dim level can the voltage across the capacitor be less than that, but enough to saturate the zener diode (which I haven't measured yet).

 

Once this dim level is determined, you could keep the channel at this level for an extended period of time, during which the 555 will continue to run, but there won't be enough voltage to light the LEDs. It will be a further experiment to determine how long it takes to get the strobes out of sync.

 

In this circuit, the 555 well generate an almost square wave. The duration of the light pulse is not determined by the 555, but by the time it takes the capacitor to discharge through the LEDs.

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Thanks Steven, I had figured as much.  But if you don't ask, you won't know, right?  :)    All my instructors always said: "The dumbest question is the one that never gets asked." :lol:

 

Appreciate the info and the schematic for the explanation.

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Someone should try a relaxation oscillator using a UJT.  The flash might be of a short duration and the energy you could dump into the LED might be greater..   Just a thought.. never tried using one on LEDs before..

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