MOTM

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?

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.

>> Also, It's not an electrical reason, but looking at UV and bright blue
>> LEDs is not that great for your eyeballs. You'll also probably drop 
>> the
>> resale value of your modules, or maybe not. It's also impossible to
>> find the MOTM style led in blue, aqua, or UV.
>
> Yeah, look out for the bright LEDs. The red ones in my Waldorf Micro-Q 
> are
> *NASTY*. I angled my rack just to avoid looking at them. Anything with 
> a
> diffused lense should be OK, but the clear ones are eye killers.

Yeah, I remember those! For an extremely misguided example of LED 
torture check out the new Access Virus "Polar". 
http://www.access-music.de/

Ugh.

--mikes

I have substituted the green Lumex leds (from Digikey) for many
of the red leds when I build MOTM modules.  I generally prefer more
green and use the red leds for indicators such as clipping.

I bought extra leds and reuse the housing to mount bicolor and blue
leds.  I have to trim the tabs inside the housing for these
leds to fit.  The Chicago bicolor leds fit and work just great.

These alternate leds are the standard dome shape and are too long
and extend out of the housing.  I simply grind off the top of the
led to flatten them and create a nice diffused surface. I then use
sandpaper in a rotary motion to smooth them off and leave a circular
pattern on the surface.

I use bicolor to indicate signal polarity such as on the MOTM-320
LFO.  They aren't as bright as the MOTM bicolors but look quite good.
I use blue to indicate MIDI for my Roland Sound Canvas module and my
Expressionmate Ribbon module.  I wouldn't want a whole panel of blue.
It would be hard on my eyes.

Dave

--- In motm@yahoogroups.com, "musik_arbeiter" <nickca@g...> 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?