Rebel tri-star wiring question

[Gilgamesh]

Hello.
Let me ask you a question on LEDs if I may, as my knowledge of wiring is extremely basic.
I know how to wire something like a Seoul, they're pretty straight forward, 2 wires, a positive and a negative. Where I get confused though, is when multiple LEDs in the star come into play, requiring > 2 wires. For instance, Luxeon Rebel Tri-Star LEDs have 3 LEDs, thus there are 6 wires. What do I do with 6 wires?? Do I just splice the 3 positive wires into 1 positive, and the 3 negatives into 1 negative? I don't care about flash on clash, I just want to maximize brightness, I plan on using 3 reds in the tri-rebel.

Thank you for any information.

[Silver Serpent]

There are two main ways to wire up a Tri-Rebel. Parallel and series, and both are valid. What you have described is a parallel wiring scheme. The other is to wire them all in a long chain, connecting the negative of one to the positive of the next. You'll end up with all three LEDs connected to each other, and only a single positive and negative wire to run back to the battery.

----- -LED1+ -LED2+ -LED3+ +++++ Kinda like that.

Power requirements change based on whether you're going parallel or series. If you're going parallel, your current will be divided equally among all three LED dice. So if you want each die to run at 700mA, you'll need to have 2100mA available for the set. The voltage necessary in parallel wiring is the same as for a single LED. It won't change.

Now in series, the current remains the same, but the voltage needed will change. If you have 3 LEDs @ 700mA and a forward voltage of 2.4, then you'll have to feed them 700mA of current and 7.2v of power.

Your battery and driver solutions will determine the best way to wire the LEDs. Also remember that you don't have to use all three dice. On the Tri-Rebels in the store, the reds are actually Red/Red/White. If you want a great red, just use the two red dice and ignore the white.

[Gilgamesh]

That was most helpful, thanks.

[mcpreaches]

Crazy I was just trying to figure this out after watching a tutorial on how to Parallel wire a Tri-Reb. But I had one question.... I want to get a Tri-Reb with these specs and wire it Parallel (All three led one color), It is a stunt saber so no sound just a resister, switch and a battery. Would Panasonic Protected 18650 3.7V 3400mAh be enough to work with that set up?


LED SPECS
PC Amber LED Color
225 Lumens @ 350mA
396 Lumens @ 700mA
- Lumens @ 1000mA
70 Efficacy (lm/W) @ 350mA
59 Efficacy (lm/W) @ 700mA
591 Typical Wavelength (nm) (1)
588 to 592 Wavelength Range (nm) (1)
120 Beam Angle (2)
700 Recommended Operating Current (mA) (3)
700 Maximum Rated Drive Current (mA)
9.6 Typical Forward Voltage (Vf) (4,5)
10.53 Maximum Forward Voltage (Vf) (4,5,7)
11.5 Thermal Resistance (C?/W) (1,6)
130 Max Recommended Junction Temp (C?)
-40 - 110 Operating Temperature Range (C?)
20 x 20 x 3.5 Dimensions L x W x H (mm)

[Silver Serpent]

In parallel? Yes, an 18650 will have no issues putting out the necessary current to power your setup. There will actually be 3 resistors, one for each LED die.

[mcpreaches]

Ok so two more questions if i may... (as always thank you for your help and patience) I tried to use your Calculator to figure out the resistors I know the voltage is 3.7 and the forward voltage is
9.6 Typical Forward Voltage
but what is the third number i have to put in. (sorry for the stupid question) and also I made up these two diagrams but I only have 1 resistor on them what should I change.
Option_1.jpgOption_2.jpg

In parallel? Yes, an 18650 will have no issues putting out the necessary current to power your setup. There will actually be 3 resistors, one for each LED die.

[Silver Serpent]

9.6v is for all three dice in series. Each individual die would have a forward voltage of 3.2v. Use that, and the current of 700mA for Ambers.

You can put the resistor on either the positive OR negative wire. Either one works, there's no difference. For this example, we'll say you're putting them on the positive wire. For die 1, connect the positive LED pad to the first resistor using red wire. Then attach more red wire to the other side of the resistor. Put black wire onto the negative pad of die 1. Repeat those steps for the other two dice. You'll end up with three red wires which you'll then join together. Join the three black wires together. That will be your LED module.

/-- (LED1) ++ res +++\
--- (LED2) ++ res +++++++
\-- (LED3) ++ res +++/

[mcpreaches]

Yup I follow, my next question is why... why use 3 resisters instead of just one? (just for my own knowledge)
Also just to let you into my mind... I have a broken UltraSaber that was given to meand I was trying to find a way to fire a Tri-Reb into it, but the heatsink only has 4 holes so I was trying to figure out a way to do that... but Also I am building a saber for my wife from TSCC and will be working away on that as well.

Thanks again sorry to ask so many questions but you have been really really helpful in my education.

9.6v is for all three dice in series. Each individual die would have a forward voltage of 3.2v. Use that, and the current of 700mA for Ambers.

You can put the resistor on either the positive OR negative wire. Either one works, there's no difference. For this example, we'll say you're putting them on the positive wire. For die 1, connect the positive LED pad to the first resistor using red wire. Then attach more red wire to the other side of the resistor. Put black wire onto the negative pad of die 1. Repeat those steps for the other two dice. You'll end up with three red wires which you'll then join together. Join the three black wires together. That will be your LED module.

/-- (LED1) ++ res +++\
--- (LED2) ++ res +++++++
\-- (LED3) ++ res +++/

[Silver Serpent]

Yup I follow, my next question is why... why use 3 resisters instead of just one?

Science time!

If you had three perfectly identical LED dice on one star, you could calculate a single resistor that would serve your needs. *However* there are slight imperfections in each LED that will cause them to draw different levels of power. For example, suppose LED1 drew a bit more power than LEDs 2 and 3, it would get warmer due to the increased current. As the temperature of the LED increases, the power it draws will also increase, leading to more heat, leading to more power draw, etc. This is called thermal runaway. Additionally, if one die is drawing extra power, then the other two will be getting less, so they get cooler, and then draw less power, etc.

Once thermal runaway starts, you tend to get one die running really hot, burning out, and then there's extra power on the other two dice. Guess what happens to them in short order? That's right. They burn out as well. Putting a resistor on each LED will prevent those LEDs from overheating and going into thermal runaway. So it keeps your LEDs safe.

[mcpreaches]

Now I know and knowing is half the battle (the other half is red sabers and blue sabers ) thanks so much for the education it makes total sense. Now I wonder... I had a somebody install a Tri-reb into one of my TCSS sabers a while back and they didn't even use 1 resistor.... Should I rewire it?
anyhow here is a new diagram I made (a lot cleaner) how does this look to you.WIre Diagram.jpg

Science time!

If you had three perfectly identical LED dice on one star, you could calculate a single resistor that would serve your needs. *However* there are slight imperfections in each LED that will cause them to draw different levels of power. For example, suppose LED1 drew a bit more power than LEDs 2 and 3, it would get warmer due to the increased current. As the temperature of the LED increases, the power it draws will also increase, leading to more heat, leading to more power draw, etc. This is called thermal runaway. Additionally, if one die is drawing extra power, then the other two will be getting less, so they get cooler, and then draw less power, etc.

Once thermal runaway starts, you tend to get one die running really hot, burning out, and then there's extra power on the other two dice. Guess what happens to them in short order? That's right. They burn out as well. Putting a resistor on each LED will prevent those LEDs from overheating and going into thermal runaway. So it keeps your LEDs safe.