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pbryan

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About pbryan

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  1. My 2008 Display came down today... In an attempt to get this thread back on track, Here are a few more observations about the 2009 Samples. Overall, I'm pretty happy with their performance. Of the 36 2008 50 ct. strings I used, 6 times I encountered problems with outages. 4 times I had to check each LED, and eventually found one needing re-seating to re-light the string. Twice the problem corrected itself(!), both times in rainy situations (which bothers me more than the ones I had to fix!). Of the 9 strings of 2009 samples I used (4 from the first batch, 5 from the 2nd) I h
  2. So far so good with the new 100ct. strings... Since all my LOR equipment is now employed outside in my display, it's been a little more difficult to test the new strings. I just added the new 100 ct. ones to my display. The green still has a little fade out when it's power is cut but it's much faster than before. To my eyes, maybe twice as fast. Plugging the 50 count greens into the wall, they appear to be basically instant off. I haven't been able to play with them on the LOR setup yet, because I haven't really figured out how to incorporate them into my display yet... I've
  3. For those of you interested in seeing the fading and on/off performance for yourself, I made a little video of the samples vs. some 2008 50ct. M5's and a 50 ct. clear mini string. The camera can't pickup all the subtleties but does a good enough job to see the major differences from string to string, color to color. Video is here: (Warning it's about 4.5 MB) http://www.paulbryanphoto.com/temp/CDI_LED.wmv --Paul
  4. Looks like a translation from (I assume) Chinese. I think what he's saying here is that a standard bridge rectifier requires a current limiting resistor in series with the LED's inside of each rectifier block. Since we're working with 120V AC, that resistor, in many cases, would have to dissipate a lot of power. In the case of the 50 count red's that some were converting to bridge rectifiers a 3W resistor was needed. That resistor will also get hot (or at least warm). Heat is bad for preventing moisture build up, and likely bad for passing UL (or other fire prevention) certifications.
  5. You'll also be adding more parasitic power usage to the string of efficient LEDs. It's not a ton more, but part of the reason for using LEDs is power savings, and part of the design should always be to minimize power usage. Too much power dissipation here causes heat as well, which isn't usually good for encasement in a waterproof housing. Reducing the size of the caps could help too, but it will change the dynamic of the circuit in it's normal operation. There is likely a trade-off here between the power off decay rate and characteristics that give us the smooth fade up/down operation
  6. OK, so I've done some testing with the LOR setup now... I have to say, I think I like the new strings... The extra capacitance (in the colors other than red), give them a little bit of a incandescent feel. I can see where animated users (such as me) using both LEDs and incandescents would like that. The effect is a little exaggerated however, as it takes a few seconds for complete darkness when you go from 100% to 0%. The greens seem to take the longest, producing some amount of visible light for almost 4 seconds. All the fades seem to be very smooth, I'm not noticing any "hi
  7. True. Probably cheaper than running 4 wires, but still more expensive than the current approach. --Paul
  8. Looks about right to me... I haven't torn open a 2009 string yet, but this is the same basic circuit as the 2008's. With a few differences. In the 08's R4 did not exist, it was shorted. There were also additional diodes on the outputs of the rectifier blobs, would have been just before R3 and just after R4. These seemed to be pointless to me in the '08 strings as they were in the rectified side of the circuit, they should never have been needed, and it appears they have now been removed. --Paul
  9. #1) First, My experience with 2008 strings is only the 50-count M5 Red, Green, & Blue strings. I have not used any other color, count, or size. The only part failing in the 2008 Red 50-ct M5's was a small surface mount resistor on the output of the male plug end of the voltage doubler circuit. If you look at Bob V's schematic (which is very close to the 2008 schematic) it would be R3. It appeared to be an 1/8 watt resistor. Replacing that resistor with the same value, higher wattage, prevented failure. I'm not 100% convinced that the overall component sizing (both power and resis
  10. My strings came Wednesday. However so did my first child (2 weeks early!) so my test time will be a little sporadic for a while. I did plug the strings in and noticed the same thing everybody else is reporting, a significant fade off in all but the red strings. I haven't put them on my LOR setup yet, but it doesn't bode well for the red fading the same as the other colors. As for the capacitors, in the 100 count strings, if you want a series string of 100 LEDs you have to use capacitors. The 3+ volt drop of the non-red colors requires 300+ volts across the 100 count string. The 2 v
  11. For 100 light strings you will either need to reconstruct the voltage doubling rectifier or break the string into 2 (or more) parallel strings of 50 (or less) LEDs. Even the Reds with their 2V forward drop require 200V across 100 LEDs. You can't get that with a simple bridge rectifier and 120V AC. --Paul
  12. Any time you are dissipating 2+ watts through a resistor it's going to get a little warm... Too hot to touch starts getting into territory where you need to worry about resistors failing and worse, melting or even igniting things that come into contact with it. Sounds like you're on the right track. Work your way from dim to bright and stop just when you get there. Bumping the current up a few mA past it's ideal value may not give you a noticeable increase in brightness, but could degrade the life of the LEDs significantly. Working up on it from the dim side should allow you to find
  13. 2 - 2W resistors will be the same as 1 4W in series or parallel. Just make sure you size the resistance right. 2 - 2W 4k's in parallel is like 1 - 4W 2k. In series it's like 1 - 4W 8k. --Paul
  14. I don't think I could choose without some testing... Got a Radio Shack (or similar) nearby? I'd want to see just how much the brightness is affected... If you can pick up a few diodes and resistors (or a potentiometer) locally you could do some testing. Putting 16-18mA through them might look just fine and you won't have to worry about anything. On the other hand, it might look too dim, in that case I'd want to see what resistance gave me acceptable brightness and work from there... The goal would be to find the lowest peak current with acceptable brightness. If you us
  15. As an example, here's a data sheet for a 5mm Red LED. NOTE: THESE ARE NOT THE LEDs USED IN YOUR STRING. http://www.superbrightleds.com/specs/r2_specs.htm These LEDs allow a Continuous Forward Current (If) of 20mA. This means you can run them at 20mA forever and they will meet all their performance and life specs. They also state a Peak Forward Current (Ifm or Ifmax) of 50mA. They also state conditions for the Ifm as 1/10th duty cycle, 0.1ms pulse width. This means you could run it without damage at 50mA for .1milliseconds if you allow it to rest with no current for .9milliseconds.
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