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Bman 12-08-2010 01:32 PM


Originally Posted by Brynn (Post 426327)
Really nifty, Bman! Reminds me of what my friend/neighbor Martin does with high-speed photography, which you might like:
Liquid Sculpture

I love how high-speed photography turns everything in to amorphous goop.

Time stretching audio is sort of the equivalent:


Brynn 12-08-2010 11:44 PM

Fun site! I found a cat's meow there to confuse my cat :)

MoJoRiSin 12-14-2010 11:33 AM

Brightpearl, the day after I read you post
About Sherlock Holmes
I listened to a sermon
(Which may or may not be posted online soon. : )
In which the sermon giver
Referred to the tv show entitled
"The Mentalist"
Mo does not watch tv hardly at all
So I went to wikipedia
Click on
"cast and characters" r a chuckle !!
Please say yes to being one of mo's
Huge smiley face goes here of course

please say yes!

Bman 12-14-2010 11:09 PM

I can't wait to wait for this show to make its way to the internet http://www.youtube.com/watch?v=aBOl1OW7nnM

Brynn 12-15-2010 03:58 PM

Little Drummer Boy

lukkucairi 12-17-2010 11:33 PM


Originally Posted by Peregrine (Post 426419)
I = V/R
I = 3V/4.3Ω
I = 0.698A

R = V x I
R = 5V x 0.698A
R = 3.4Ω

So yes, it can, assuming constant amperage, and an initial resistance of 3.4Ω*.

*unless I fvcked up.

I don't know what the initial resistance was! I suck.

I may have fudged the numbers but it's a series of 20 RGB LEDs, at 20-30 mA each, that usually runs off a 4.5V battery pack. The voltage tolerance for the LEDs is approximately between 3V and 3.8V (as far as I can tell by looking at similar LEDs at online providers) so a friend of mine suggested that the battery pack itself was providing resistance (as there is no resistor wired into the original assembly) - plus the batteries lose voltage pretty quickly right at the beginning of the power curve so even if the initial voltage with new batteries is at or over the top of the range it would soon fall off into the 'happy zone' - and I guess with a set of 3 x AA batteries you wouldn't have to worry about voltage spikes that might fry the array like you might with mains power through a wall wart.

Of course, running three of these strands off a 5V 2A DC wall adapter is what I've been trying to do. I'd appreciate if you'd check my work:

With a couple of flying guesses I calculated that two 2Ω 2W resistors would provide approx. 1.4V of drop in the power coming from the adapter, which would put the working voltage to the strands at 3.6V, within the tolerance range of the LEDs. Wiring these resistors in series one right after the other would be a pain in the ass structurally so I put one at the + end of the strand and the other at the - end. And no, the local electronics store didn't have any 5Ω or 4Ω resistors available, so wiring in the pair of 2Ω was the best I could do on short notice. As I understand it this should give the same result as putting them one right after the other but I could have the wrong end of the stick (or the LED strand, as the case might be).

I put this whole thing together as I just described, and I've been doing a power test for the past two hours to see if anything is going to overheat or go poof. So far so good...

lukkucairi 12-17-2010 11:39 PM

^ btw that's three strands in parallel, not in series.

Peregrine 12-18-2010 02:20 AM

Wow. Um. To be honest, I actually had to Google Ohm's Law to come up with that, since I haven't done this since my undergraduate physics lab, like 9 years ago. You're actually, way ahead of me at this point.

I keep misunderstanding the problem, so I've come up with 3 or 4 wrong answers, and it's after 1am in my time zone, so I'd better quit while I'm ahead. But if I ballpark it, I'd guess you're going to want to drop it down another couple of volts.

What I would actually do is get a multimeter, and measure the resistance contributed by one of the diodes. That would probably give you better numbers to deal with. If you're hooking diodes up in series for each strand, then the resistance across the series is the sum of the resistance of all the diodes in the series. For more than 2 resisters in parallel, it's the sum of the reciprocal.

You could probably even measure the voltage across each strand. That would probably give you a better idea if you're overloading the system or not.

Bman 12-18-2010 02:28 AM

What are you guys making o_o

MoJoRiSin 12-18-2010 03:31 AM

^something to do with lighting up the sky?

MoJoRiSin 12-18-2010 03:33 AM

:) :) :)

brightpearl 12-18-2010 11:35 AM

I love you, Lulu.


zero 12-18-2010 04:28 PM

lukkucairi 12-19-2010 12:38 AM

I can't use the ohmmeter to measure the resistance of the strand because there are little chips in each diode lens and they don't make a complete circuit :p


Thank you for having a whack at it Peregrine :)

I'm going with what I've got for now. It's been running all day and seems to work :o - no diodes frying and no resistors heating up unduly. I've got the materials to build another set so next time I'll up the resistors and see what happens.

trisherina 12-19-2010 01:54 PM

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