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Author Topic: Purple Color mixing  (Read 914 times)

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Offline Controverze

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Purple Color mixing
« on: January 29, 2017, 06:55:26 AM »
Hello,

I have got a custom Luxeon Tri Rebel regular Blue, regular Red, neutral White.
I read everywhere that red is too bright, but in my case it is the opposite.

In common sense the blue is brighter than red and so it does wash out my red led completely.
I have an 0.5Ohm 3W resistor on blue and a 1.5Ohm 5W resistor on red.
Those are recommended for the protection circuit, but as stated above, they are not helping with mixing.

Did I perhaps buy the wrong led setup?
I'm kinda sceptical about using high resistors because they reduce the brightness of my saber...

I'm asking for help because I don't feel like buying a whole range of resistors to test it out, it's a waste of money.
Or is there a better way of doing it without resistors?

Offline theholyduck

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Re: Purple Color mixing
« Reply #1 on: January 29, 2017, 07:39:13 AM »
Resistors is the easy way of doing it but yeah. it isn't perfect. the only way to actually do the color mixing is to dim the blue or run the red even brighter. and your current resistor setup is already over driving the red. you need a higher resistance on the blue to dim it down.

if you dont want to just/only use resistors. soundboards with multiple outputs that can do dimming using PWM or current regulation can be used to fine tune or completely tune your color mix.

Offline jbkuma

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Re: Purple Color mixing
« Reply #2 on: January 29, 2017, 07:40:12 AM »
What are you basing your calculations on? What's the Vf for your LEDs?
Based on the values listed on ledsupply for their RGB star, Red has a Vf of 2.9, Blue 3.15
The calculated values for the resistors @ 3.7v would be 1.14ohm @ 700ma for red, .55ohm @ 1000ma for blue.

Offline theholyduck

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Re: Purple Color mixing
« Reply #3 on: January 29, 2017, 08:00:50 AM »
tccs has their luxon rebel red leds as being 700ma at 2.4v giving you a 1.85 ohm for 3.7v nominal.

Offline Controverze

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Re: Purple Color mixing
« Reply #4 on: January 29, 2017, 08:03:36 AM »
I used the data sheets on ledsupply also, this is where I got them, and used the single colored stars as a reference.
And I used Rob Petkau's explanation to do it.

That would make 3.7V battery at a max of 4V - 3.51V VF max for blue = 0.49/1000mA = 0.49Ohm. Which is 0.5Ohm.
4V - 2.8V Vf max for red = 1.2/700mA = 1.71Ohm. Closest by is 1.5Ohm to be reasonable, higher (which is normally the rule) was too high.
« Last Edit: January 29, 2017, 08:05:46 AM by Controverze »

Offline Darkjedi

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Re: Purple Color mixing
« Reply #5 on: January 29, 2017, 08:27:37 AM »
Ok you never said what board you are using if you are. If you have R.I.C.E or another board you could mix them that way on your computer

If you are not using a that then the easiest way would be to wire in potentiometers or pots, it acts as a variable resistor to get the mix you want.

Offline theholyduck

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Re: Purple Color mixing
« Reply #6 on: January 29, 2017, 08:33:30 AM »
anyways. the result is the same. you need to dim the blue as you cant really drive your red much higher. pots arent normally rated for the sort of amperage you would want so either get a few resistors to play around with. or use a soundboard which allows individual mixing of leds.

Offline Controverze

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Re: Purple Color mixing
« Reply #7 on: January 29, 2017, 08:37:37 AM »
I'm using a Nano Biscotte V3 soundboard as this was the cheapest for a decent board.
This was my first custom build, did everything myself. Good thing i also have a lime/lime/white, these are wonderful tho.

I know a lot about electronics and the use of pots, but because I built it into a SF Archon, I don't have enough space to put pots in there.
Well at least not the ones available to me in Belgium/Europe. What range would you suggest in a potentiometer?
And what sould the minimum load or Watts be?

The only thing I hate now is that my resistors ramble about inside my hilt.
« Last Edit: January 29, 2017, 12:12:21 PM by Controverze »

Offline erv

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Re: Purple Color mixing
« Reply #8 on: January 29, 2017, 09:42:38 AM »
led's Vf must be measured if you want accurate resistor setup and fine color mixing

Offline Controverze

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Re: Purple Color mixing
« Reply #9 on: January 29, 2017, 01:45:59 PM »
I don't need it to be perfect, I just need some values to work with really.

I'm about to try with a potentiometer.
Now I just need to know which resistance value (1 kOhm more/less) and which load (1W more/less) is suited for this blue led on that battery

Offline jbkuma

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Re: Purple Color mixing
« Reply #10 on: January 29, 2017, 03:46:15 PM »
Or you can just try adding spare resistors in series to see if you like the mix you get.

Offline QUI-GON JINN

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Re: Purple Color mixing
« Reply #11 on: January 29, 2017, 04:46:20 PM »
Common practice for color mixing without a sound board capable of doing it for has usually been to use a potentiometer to "dial-in" the color you're looking for,  measure the amount of resistance,  and replace the pot with the closest resistor to the value you measured.


Offline Controverze

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Re: Purple Color mixing
« Reply #12 on: January 30, 2017, 06:03:55 AM »
So basing on what you are saying I take it wouldn't be recommended to leave the potmeter in the circuit inhilt?
If otherwise what should the potmeter Wattage be to handle the load on the led module?
The last thing I want to do is fry my circuit in the end, as I don't always know which values to use to calculate it

Offline darthgrant

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Re: Purple Color mixing
« Reply #13 on: June 30, 2017, 09:32:52 AM »
maybe i should spend more time here...... i was literally trying to figure this out the other day..... oh- I'm so excited to finish this build :)