question about RBG LED for crystal chamber

[lelegossalas]

Hello,

In the CF manual, I don't see the voltage output for crystal chamber RGB LED, only max current info (18mA). I guess that it is 3.3V like other accent pads ?

While looking for the led to buy, most of them have at least one channel with 3.3V. I only foung one under 3.2, but light intensity appears low (40-70mcd, vs 450-700 for 3.3 LED). I don't know how to calculate the resistor for 3.3V led, and not sure it is possible by the way (as I know, 3.3V pad less 3.3V LED ==> 0 ohm ==> no current control).
But some members use (or have tried to) some 3.3V.
Can you confirm it is possible (or not), and how to calculate resistor ?

I have read that there might be some trouble when channels have very different light intensity.
Depending on the available space of the chamber, maybe should i use alternative scheme using 3 red, green and blue LEDs with similar caracteristics ?

Thanks.

[Jedi_Corellian]

Hey lelego,

You may want to try reaching out to someone in the Custom Saber Shop forums or anyone within the S.A.B.E.R Guild or VIP forums.

Hope this helps!

[lelegossalas]

Hey,

Thanks for you reply, forum looks quiet. I guess that's summer holiday effect, everybody is on the beach :)

I think I'll probably do some LED testing, that will be the best.
All I need is to know if I can order 3.3V LED, I'll try your suggestion. Latching AV switches with ring LED sold by TCSS also use 3.3V LED.

I have tested one online resistor calculator that says 1 ohm, but i'm not sure result is reliable in this case.

[Scarecrow]

The output for the PWM signals (color channels) is 3.3V @ 18ma.  The accent pads put out the same.  If you want to resistor your 3.3V leds then you can calculate for 10ma.  I don't resistor mine and I haven't run into any trouble.  Do so at your own risk.  If you use two of the same leds in your crystal chamber then you shouldn't run into any issues with varying brightness.   

[Jedi_Corellian]

Hey,

Thanks for you reply, forum looks quiet. I guess that's summer holiday effect, everybody is on the beach :)

I think I'll probably do some LED testing, that will be the best.
All I need is to know if I can order 3.3V LED, I'll try your suggestion. Latching AV switches with ring LED sold by TCSS also use 3.3V LED.

I have tested one online resistor calculator that says 1 ohm, but i'm not sure result is reliable in this case.

Absolutely not a problem. Yeah, the forums do seem a bit quiet lately...Hope all goes well with LED's!

[lelegossalas]

My holidays have just started, now I will be able to work hard on my project and make all orders I need :)

The output for the PWM signals (color channels) is 3.3V @ 18ma.  The accent pads put out the same.  If you want to resistor your 3.3V leds then you can calculate for 10ma.  I don't resistor mine and I haven't run into any trouble.  Do so at your own risk.  If you use two of the same leds in your crystal chamber then you shouldn't run into any issues with varying brightness.   

Well, if the soundboard has a protection system not to drive higher than 18mA, and if the 3.3V LED is 20mA or higher, no resistor should work.
CF manual says Accent LED should have "forward voltage lower or equal to 3.3V", so I think that's OK. Maybe because of my technical english and my low knowledge in electronics, this point is not clearly described for me.

I dont think I will try unresistored, unless erv confirms there is no danger for the board (LED is cheaper and more easy to get, so doesnt really matter; even if better to keep it safe, of course).

[Scarecrow]

There is no danger to the board, just the led.  Hopefully, Erv will chime in so you can get started on your build.  There's nothing like the sense of accomplishment when you fire one up for the first time.