Purple LED?

[nartules]

Just thought I would mention something, for anyone who ever runs into a website in another language, there are free tools on the web to help.  I used to bid on auctions at yahoo japan and had decent success even though I don't speak or read japanese.

http://babelfish.yahoo.com/  offers translation services for phrases, as well as entire webpages.

[PhoenixJedi]

Most of us use LEDEngin RGGB, RGBA or RGBWs.

[SithStalker]

I have a purple RGB in my Mara Jade lightsaber.  :D

[Darth Nater]

I figured to post here rather than start a new topic, because that seems to be frowned upon in several forums if its a similar discussion.   And I'd be thankful for any advice no matter how elementary it might seem.

I have a DX RGB that I'm wanting to run off a 6V 4AAA setup through a hasbro obi wan board.   No doubt trying to get purple out of it.  Its the normal econo board wiring setup through the TIP42 transistor, though I might choose to put an illuminated switch in the final build.  Just testing at this point. 

I got three 3W 25ohm potentiometers at radio shack today.  Wired the positive out of the transistor to the single negative on the DX star (mislabeled LED so call it the positive I guess).  Wired the 3 negatives from the LED parallel to the 3 pots, and then parallel from the pots to the battery negative. 

I used a multimeter on each pot to make sure the resistance was at a safe setting (not too low) and I used the settings for a 6V power source for each die.  (I couldnt figure out how to meter the soundboard to get actual voltage after the TIP42.  Tried holding there and to the battery negative, but never registered a number.  Dont know how to do this evidently)

The LED is sitting on a large heatsink taken from a broken Xbox 360 so no heat issues.  But I dont have it in a blade holder and don't have a lens on it either.  Upon powering it up, it works, but I can't really tell much by way of color.  Really just looks white mainly.  I removed a blade from another saber and held over it while I messed with the pots, but it didn't do much by way of being able to see a lot of difference.  I had the green trimmed back to 25ohms and I figure this would really dim it.  Finally just disconnected the green.  From there, its a whitish pink.  No color was ever very bright, they were all mainly white.   The lowest I ever let the blue get was around 7.5ohms and the red maybe 12.

Tell me that having it in a blade holder with optics and a blade attached is a requirement for testing.  Thats one thing I didnt do.  I've got no clue how to do this evidently.   Probably spent 6-8 hours over the past few weeks searching for topics on what parts, where to get them, how to color mix and asked minimal questions out of fear of being told to read more. 

Any help would be greatly appreciated.

[LUMINARA UNDULI]

Well, normally, we use a 1W 250 ohm potentiometer.  The reason why we use the 1W pot is because we replace the pot with a 1W resistor.  Using the 3W pot, the reading you are going to get is going to be for a 3W resistor.  Good luck finding those :-\.

You only put the pot on the red.  The blue gets wired direct.  The green doesn't get wired at all.  I would remove the board from the mix to start out with, to make sure the LED is OK.  The LED should be bright.  Then put the board back in the mix.  If it is significantly less bright you have a problem with the wiring of the board. 

To get your color mix, you are going to need to make yourself up a test set up.  We normally use a TCSS heatsink, with a bladeholder, lens and LED so we can put a blade in.  Without the blade, you are not really going to be able to tell the color.  The color, also, will vary with which blade type you use, so you should have the blade you are going to use with the saber.  Once you have all this set up, adjust the pot until you get the color you want.  Measure the resistance with your meter, and you should get the correct ohm reading.  Then, replace out the potentiometer with the correct resistor.

[Darth Nater]

Ok, in the process of reading and going the DIY route, I've basically misunderstood half of the things I could have probably answered had I had the nerve to ask questions earlier.  From what I gathered, whether it was a 1W or a 10W wouldn't make a difference on the measured ohm resistance.  The pot would just be rated higher.  Strike 1 for me. and a wasted $15.

Also, I though that if you let the 6V source go straight to the blue die with no resistor, you would fry it.  Maybe I should throw in a dummy cell and use 4.5V instead.  The board is wired correctly for its purpose.  Its the same setup I have running a P4 red and another with a P4 green (both resistored) and the LED is bright, but the colors aren't bright.  They are more white than they are anything else.

The last part I kind of assumed.  I dont have the bladeholder and stuff yet, but wanted to mess with it anyway.  I knew that the blade was the primary thing in mixing the colors (more so than the lens from what I've read).  I'll just have to wait on that part.  But the one thing that has me puzzled is how to meter the board.  I assumed a multimeter on the positive out of the board and the negative to the battery, but that didn't work for me.

Will the blue with no resistor not get fried?  When I plug this into a resistance calculator (6V power source, 3.5 forward Voltage, and 350MA), it says it needs a 2W or greater 8.2ohm resistor.

[Darth Nater]

This project has completely sucked.  I've got the blade  & holder setup to test now, but every freaking resistor combination looks strikingly similar.  A very pale whitish wannabe purple.   Likely giving up and using the RGB for a nice Cyan.  It seems pretty capable of that.  Maybe pickup a white P4 someday and a lee filter for another shot at purple. 

I've tried my setup through the econo board and PNP transistor with the blue using both a 2.7ohm 1W resistor and swapping out with a 3.3ohm 1W resistor depending on if I use 4AAA or 3 with a dummy cell.   Have tried the red with 8.2ohm 1W, 12ohm 1W, 10ohm 2W, and 12ohm 2W.   Have also tried the red with the 3W potentiometer just to see as well as a very brief look at the red on a 3.3ohm 1W (which would likely fry it if I didnt just touch it there for a second to see).   Not much difference in colors between any of these setups.  4.5V into the econo board sucks.  6V is bright enough, but maybe they just don't mix well.  Its a white thick blade with about 5ft of clear celophane inside.  5 degree lens.

[LUMINARA UNDULI]

White thick blade is going to wash out your LED no matter what color and make it pale and whitish.  If you are using 4.5V you do not need to resist the blue.  The resistors you are using on the red seem high to me.  I usually find the range with 4.5V is closer to anyplace from 3.9ohm to 5.7ohm in a 1W.

[Darth Nater]

I got all of my resistor numbers off that LED resistor calculator going off 350MA, (4.5/5/6 volt combinations) and the forward voltage that DX had listed.  I was under the impression that going lower than that would fry the LED.   

The white thick blade looks just fine with red or green P4's.

So not resisting the blue at 4.5V and dropping the red to that lower ohm range won't burn out the dies?  This was mainly what I was worried about (and probably another reason why 4.5V was so much dimmer overall.   I bought 3 of these things since they were cheap, so I guess I can try this and if it burns out, just swap in another.

[LUMINARA UNDULI]

Of the several hundred DX RGB LEDs we have done, we have burned out about 5 maybe, and that has been primarily with MR boards that are hard to know the exact output.

4.5V should not blow out the blue.

[Simpi-Gon Sims]

4.5V should not blow out the blue.

What about 4.8V ?  :P   ::)

Im in the process of doing something similar Nater, but with an MR board. Don't give up. You can do it!!

[QUI-GON JINN]

That works as well,  I've used an MR board with one of those DX RGB's before,  and just put a resistor on the red,  not on the blue using a 4.8v battery source.

[Darth Nater]

Thanks for the advice.  I'll tear this back apart and try some other combinations.  I'm still not sure how many volts I'm getting out of the econo board through the transistor.  Still havnt figured out how to meter it yet, but will try that again as well.

[Simpi-Gon Sims]

Thanks for the advice.  I'll tear this back apart and try some other combinations.  I'm still not sure how many volts I'm getting out of the econo board through the transistor.  Still havnt figured out how to meter it yet, but will try that again as well.

You should be able to meter it just on the LED star if you wanted. Turn to your voltage setting (DC) on your multimeter and measure it. Just be sure to cover the LED with something so you don't blind yourself.  ;D

[Darth Nater]

Not sure if I did this right or not, but I put the multimeter positive on the positive coming out of the PNP transistor, and then to the negative coming out of the led.  Granted there are 2 negatives coming out (one red/one blue) and using 4AAA in the pack, I got a reading of about 3.25 volts from the blue.  The reading on the red was a little lower.

With it being an econo board and having to use a transistor to get enough voltage to power the led, this almost makes sense.   And if it is correct, then I have way too much resistance.  


Also, looking back at this thread, mine looks right about the same as this guy's.

http://www.fx-sabers.com/forum/index.php?topic=28853.0


I never really got a shade that I liked.  Regardless of how I've set this up, and even with the potentiometer on red, its either a pinkish purple at one end or a whitish purple on the other.  I'm starting to think the white translucent blade may be what makes it look crappy.   The single color LED sabers that I used with the thick white blades look good, but this may be whats whitening the RGB led out.