Crystal Chamber RGB LED resistors

[Darth Nurse]

Ok, so after doing the calculations for a RGB LED for my crystal chamber, I wind up with the following:

PRIZM 3.5 using the PWM legs from the main LED pads which output 3.3v

Common cathode LED @ 10mA

RED 2V = 150ohm 1/8w resistor

Blue 3.2V = 10ohm 1/8w resistor

Green 3.2V = 10ohm 1/8w resistor

Now, with those numbers, is it worth locating and using a 10ohm 1/8w (or 1/4w) on the B&G? I see TCSS does not carry a 10ohm in 1/4w. Or, is it close enough to run without on those two legs?

[Darth Nurse]

No one has thoughts on this?

[Cire Yeldarb]

well I can tell you that if your calculations are correct, you would NOT want to run the die without the 10ohm resistors... 1 ohm you can probably get away with skipping, but not 10ohm

[Darth Nurse]

well I can tell you that if your calculations are correct, you would NOT want to run the die without the 10ohm resistors... 1 ohm you can probably get away with skipping, but not 10ohm

That's what I am looking for, discussion of the threshold to skip the resistor (or run one, etc...). That to me is not something that I have found discussed when talking about saving space or wiring in general.

The closest thing is the store is an 18ohm 1/4w.

[NanoRex]

You should be fine if you leave out the resistors for the blue and green. It's only the red that really needs it.

[rlobrecht]

You should be fine if you leave out the resistors for the blue and green. It's only the red that really needs it.

Doesn't this only apply to the Rebel or Cree high power LEDs we use for blades, not for accent LEDs?

I would probably say that if the calculation tells you to run a resistor greater than 0.5 ohm, you can't skip it. That said, those resistors are so small, why bother to skip it? A 10 ohm resistor is large, but you will definitely need that one.

[CET]

Personally, I just use a dyna-ohm resistor for my crystal chambers. Then again, I'm not sure what kind of LED you're using. I typically use 20mA LEDs. I'm considering doing an RGB crystal chamber with an RGB 20mA LED. I think the dyna-ohm would still be appropriate. I would just need 3 of them.

[Darth Nurse]

Personally, I just use a dyna-ohm resistor for my crystal chambers. Then again, I'm not sure what kind of LED you're using. I typically use 20mA LEDs. I'm considering doing an RGB crystal chamber with an RGB 20mA LED. I think the dyna-ohm would still be appropriate. I would just need 3 of them.

Dyna-ohms are nice but large. The resistor for the B and G will be smaller.

[CET]

Dyna-ohms are nice but large. The resistor for the B and G will be smaller.

You're right, 1/8 watt resistors will definitely take up less space. I just hate having even more types of resistors floating around my tiny workshop. Call it laziness.

[Darth Nurse]

I got in some of the 1/4w resistors, and they are VERY small. Much smaller than I anticipated, so it looks to be a non-issue.