The master has spoken

[rlobrecht]

madcow has posted another awesome tutorial on the NBV3 with flash on clash. Starting at the 8:55 mark he talks about 1 resistor vs. 2 with a BBW LED. Being the lowly padawan that I am, I'm just going to leave this hear to prompt a discussion.

[Forgetful Jedi Knight]

This is simply going to be a case of Masters disagreeing. Madcow isn't technically wrong, but I feel the way I teach it is easier on beginners.

[Greenie]

That's how I wire mine. It's a tutorial for beginners from the master, he wouldn't show us if it wasn't right.

[Silver Serpent]

FJK and I prefer to teach the "every die gets a resistor" method. It's a general rule, and you can always use it. Madcow has shown that there are exceptions to the rule where you don't *always* need to use a resistor on each die, and he is correct.

I prefer to teach the general rules first, and let people learn the exceptions later. Resistors, LEDs, soldering, wiring diagrams, etc. can be terribly confusing for someone who has zero experience with these things. If you try to teach the exceptions at the same time you teach the general rules, you'll get padawans wiring up reds and blues with a single resistor on a 7.4v application, and then wondering why our (misunderstood) advice caused them to blow up their sabers. I'd rather err on the side of caution, since I never know how much electronics experience a newcomer brings with them. When I see a post count <10 and a request for resistor help, I'm going to assume they've never done this before.

[Madcow]

Excellent input all.

Also keep in mind that even though I have been doing this for over 17 years I am NOT a trained electrician, and some in this hobby are. There's no problem learning from different perspectives. I am a big believer in the "there's more than one way to skin a cat" philosophy.

[rlobrecht]

FJK and I prefer to teach the "every die gets a resistor" method. It's a general rule, and you can always use it. Madcow has shown that there are exceptions to the rule where you don't *always* need to use a resistor on each die, and he is correct.

Very well said.

[Greenie]

SS, that explaination is the best answer. I am a trained electrician and sometimes I forget to consider other peoples skill level. (my bad?)

[Noyl Wendor]

I personally dig both perspectives. More often than not I go with resistor on both leds. There are the occasional times when I go with one.
I've been at this a while too, but when it comes to most of it I consider myself noob status still. So many things to learn I dont know, it's hard to consider my self skilled. Once I figure out a way to do something in building a saber, I look for other techniques. Helps to grow the arsenal of knowledge

[FenixFire]

This is simply going to be a case of Masters disagreeing. Madcow isn't technically wrong, but I feel the way I teach it is easier on beginners

FJK teaches the safest most foolproof way.

The single resistor (mass production method) theoretically and in most cases it is probably ok to wire with a single resistor as long as the following variables are met. (Speaking from product design not saber building experience.)
1. Both dice are the same manufacture (MFG also needs to demonstrate consistent quality)
2. Both dice are the same color, exact bin
3. Both dice are from the same build/date code (mfg line and daily run) small differences may be present from line to line.

Worst case if these are not met one LED might have a higher power draw than the other and create a runaway voltage condition blowing one or both LEDs. More likely one will light slightly over driven and the second either won't light or will light fairly dim.

If space is a premium, then consider the single resistor if you can verify each LED has the same voltage drop. If you can't you need to ask yourself if a $20 LED is worth a $0.25 resistor.

[snilam]

ask yourself if a $20 LED is worth a $0.25 resistor.

^^^this