Check my math please?

[MikeC13]

...I'm pretty confident about everything else this involves, but math has always been my weak link.

Source voltage: 3.7v Li-Ion
R=V/I -
Tri-Cree Royal Blue: (3.7v - 3.4v) / 1A = .30 ohm
Tri-Cree White: (3.7v - 3.15v) / 1A = .55 ohm
Blue accent for crystal: (3.7v - 3.2) / 1A = .50 ohm
Green accent for power indication: (3.3v - 2.2v) / .25 = 4.4 ohms

P=R*I^2 -
.30 * 1 = .30
.50 * 1= .50
.55 * 1 = .55
4.4 * .0625 = .275

Therefore (sticking to TCSS stock resistors)
Tri-Cree royal blue: .47 ohm .5 watt (blade)
Tri-Cree white: .5 ohm 3 watt (FoC circuit) (will a slight overdrive be a problem in a momentary use circuit? Can I adjust the fdrive to compensate if needed?)
Blue accent: .47 ohm .5 watt (crystal)
Green accent: 4.7 ohm 5 watt (board power indicator)

Am I on the right track with this?

[darth_chasm]

I don't think you want 1A for the blue accent. If it's a 3-5mm you want 30mA max. Otherwise seems fine to me. Be aware that 5w resistors are quite big. Plan your space accordingly.

[MikeC13]

I was going to use a 5mm blue I have left over from an old r/c project.

So (3.7v - 3.2v) / .30 = 1.67 - 2 ohm 1 watt?

I have planned some space between the crystal chamber and heat sink, as long as we're not talking about an abnormally huge component.

Thanks for helping, much appreciated...

[darth_chasm]

Sorry looking over this again and you are a decimal off on your accent LEDs. Should be 0.025, 0.03. So move the decimal over to the right.

Generally, the white rectangle 5w ones are around 3/8 w & h and between 3/4 to 1 inch in length. But in this case you won't need 5w

I should hold my replies till after work ;)

[MikeC13]

Decimals is where I always get confused. Thank you for helping me.

Revision 2.0:

Tri-Cree Royal Blue: (3.7v - 3.4v) / 1A = .30 ohm
Tri-Cree White: (3.7v - 3.15v) / 1A = .55 ohm
Blue accent for crystal: (3.7v - 3.2) / .03 = 16.66 ohms
Green accent for power indication: (3.3v - 2.2v) / .025 = 44 ohms

RB - .30 * 1 = .30
W - .50 * 1= .50
B - 16.66 * .0009 = .015
G - 44 * .000625 = .0275

That puts all wattage requirements under 1/2 watt, so no big resistors.

It just figures that the Radio Shack right near me recently closed for good :mad:

[Forgetful Jedi Knight]

The 1/4W resistors will be fine for your purposes. What are you running the accents off of (sound board)?

[MikeC13]

I was thinking of using the 3.3v aux pad to power the green for a board is powered indication, and splicing off of the LED output for the blue (crystal) so it shares the pulsing effect of the blade. Board will be a Nano Biscotte...

[Forgetful Jedi Knight]

OK. Most accents run at 20mA as a FYI, and that's what the accent pads put out. That's what you should use for your calculations, not that it'll make much of a difference.

[MikeC13]

Thanks for your input FJK. I've been trying not to bother you guys when about everything you'd need to know is either here or a quick Google away, but I wanted to make sure I get this part right. The resistor values I can't get from TCSS I have saved in eBay. Of course, the few resistors I already have on hand don't come close to my needs.

I have to say, this is a fascinating pursuit. I'm enjoying the change from strict metal work. It feels good to knock the dust off my brain :rolleyes: