MOTM

At 5:30 AM +0000 2004/11/15, musik_arbeiter wrote:
>Is there any electrical reason why I couldn't simply swap the red LEDs
>on my 101 and 390 modules for blue ones, or possibly some other nice
>color like ultraviolet or sea green? Would I have to do anything
>besides just soldering one in place of the other?

In most cases you can't just swap the LEDs. The biggest problem with 
blue LEDs is that they are much brighter than your typical red or 
green LED (although there are also high brightness red and green LEDs 
available). To decrease the brightness, you'll need to increase the 
current limiting resistor substantially. I will typically increase a 
1.5K resistor to 15K when swapping from a red to a blue LED to keep 
from going blind. If you've ever seen the blue LED on the back of an 
Andromeda, you'll know what I mean (I keep mine covered up with black 
electrical tape).

The 101 is even trickier to do an LED swap because the forward 
voltage drop across the LED is different and changing the current 
limiting resistor affects performance. So you can't just swap LEDs 
and change resistors. I've got some notes on using a blue LED with a 
101:

http://www.tellun.com/motm/mods/motm101/motm101.html

I can't comment on the 390 because I haven't built mine yet, but I 
will likely change the LEDs in it as well when I get around to 
building them.

BTW, careful with violet LEDs because they do generate ultraviolet 
light which is bad for your eyes.