NOOB converting Hasbro Saber

[Tom Tilmon]

I am a NOOB.

I can solder, and actually made boards in shop class in hs. I'm pretty decent with electricity, understanding the basic concepts of switches and circuits. I am not good with math, at all. I have been reading multiple threads on resistors for LED's and calculations for your resistors based on ohm's law. So, here we go again, and I am sure you mods get sick of this, but I have a question.

First off, I've started by studying this:
"Ohm's Law - the down and dirty guide to "Doing the Math" yourself.
Ohm's Law comes in two parts, meaning there are two values you need to calculate. The "Ohms" value and the "Watts" value. The formulas for both are as follows:
R <Ohms> = (VfBattery - (VfLED1 + VfLED2)) / I
Where:
Vf Battery = Battery Voltage (usually either 3.7V or 7.4V)
Vf LED1 = Forward Voltage of LED #1
Vf LED2 = Forward Voltage of LED #2 (If you have a second in series)
I = (in Amps) Current you wish to run your LED at (Rebel Reds and Red-Oranges are usually 700 mA, Cree Reds, Red-Oranges, and ALL Blues, Greens and Whites are usually 1A)

The second part of the formula is as follows:
P <Watts> = R * I^2
Where:
R = the resistance value from the first calculation
I = (in Amps) Current you wish to run your LED at (Rebel Reds and Red-Oranges are usually 700 mA, Cree Reds, Red-Oranges, and ALL Blues, Greens and Whites are usually 1A) - This value needs to be squared in your calculation.
In the following example, I calculate a resistor value for a single Rebel Red LED
(Vf= 2.4V) running at 700mA running it off of a 3.7V battery.
R = (3.7 - 2.4) / .7 ==> 1.3/.7 ==> 1.86 ----> Rounded up to 2 Ohms
P = R * I^2 ==> 1.86 * (.7)^2 ==> .91W ---> Rounded up to 1W
Since there are only so many values that are commonly produced, it will be very likely that your will need to round UP to the next resistor size, to get the resistor that you would need (and as I did in the above example).
So, I will need a 2 Ohm, 1W resistor. "

So, back to my build question. I am doing an entire re-do of the Kylo Ren Black Series lightsaber, me and everyone else. I have bench tested one component at a time, but have not tested the red LED's out of "resistor fear". I want to make sure, absolutely sure that I am using the proper resistor on each red LED.

LED's I'm using on this build: Main Blade Red, Red, White XP-E2 Coppernova. My understanding about this LED, is that it is driven by 2.65 volts at 1000 mA....or 1A.

Side Emitters: Red XP-E2 Coppernova. My understanding about this LED, is that it is driven by 2.65 volts at 1000 mA....or 1A.

Battery: 3.7 volt LiIon rechargeable battery..18650 with internal protection by Panasonic.

My calculations:
TriCree Main Blade
R=(VF Battery-VF LED)/1
R=(3.7-2.65)/1
R=1.05/1
R=1

P=R * I squared
P=1 * 1
P=1

So, based on this, I need a 1 ohm 1 watt resistor for each of my red LED's on my tri-cree? I have looked at resistors on TCSS, and the closest I see to this is 1 ohm 2 watt. How will the higher wattage of that resistor than is in my calculations affect my LED?

Side Emitters:
R=(3.7-2.59)/1
R=1.11/1
R=1.11

P=1.11 * 1 squared
P=1.11

So, again, it looks like rounding nets me a 1 ohm 1 watt resistor for the single red LED's. Should I round up to 1.2 ohms here, and if so, the only resistor I see close to this is the 1.2 ohm 3 watt resistor on TCSS (currently out of stock).

IF I order the 1 ohm 2 watt resistors from TCSS, will this work? Also, does it matter which circuit I wired them into? I was going to put a resistor on each negative feed for each red LED. I have bridged all the positives on my tri-cree, so I have one positive feeder wire going up the hilt. Coming out of the Tri-Cree, I have 3 negative wires (one for each red LED, and one for the white LED). So I have 4 wires coming out of my tri-cree. One positive, and 3 negatives. 2 of those negatives are coming from the red LED's and require a resistor. I was going to put the resistors between the LED and board, wherever it wouldn't cause binding issues with the battery/card/speaker chassis from TCSS that I'm using.

The side emitters are much simpler. Common positive branching out in hilt feeding both side LED's. Independent negatives returning to the board with a resistor on each between the LED and board.

So, in total, I will have 4 resistors in my build. 2 on main blade, and one for each side emitter. My question is: is this plan sound? I'm sorry if this is repetitive for you all, but I am trying to learn.

Alternative from reading. I read in one of the threads that you should never drive a red LED with more than 700mA. So re-doing my calculations based on 700mA nets me the following resistor plan:

Tri Cree: 1.5 ohm .735 watt

Single LED Coppernova: 1.6 ohm .784 watts. ?? I don't know quite what to do here.

Tom

[Tom Tilmon]

Well, I went with 1 Ohm, 3 Watt resistors and bench tested. Everything appears to work fine. Now, I'm waiting for the conversion kit, and then I think this project will be done.

Thanks.

Tom

[GregTheForce]

Yes the one ohm will overdrive them a little but it would still work. Anyways go to a hardware store or something like that for the 1.2 ohm if you want to be on the safe side. At least that is what I did.

[Tom Tilmon]

I have looked around at every Radio Shack and hardware store I could find in town. The only place I haven't checked was Grainger. I'll check them this weekend. Thanks, this hobby is a lot of fun, but it stinks waiting on parts. I appreciate the feedback. Being new to this "hobby", I just wanted to make sure.

[Tom Tilmon]

Yes the one ohm will overdrive them a little but it would still work. Anyways go to a hardware store or something like that for the 1.2 ohm if you want to be on the safe side. At least that is what I did.

I found the 1.2 ohm 3 watt resistors at Mouser Electronics, then TCSS got them back in stock. I will be installing these resistors to avoid over-driving the LED's. Thank you all for the assistance. I think I was over-thinking this stuff.

My saber looks great, can't wait to button it all up when the conversion kits are re-stocked! I have now found another hobby.

Tom