Re: Installing an LED

On Fri, 08 Dec 2006 11:10:23 -0600, John Fields
<jfields@xxxxxxxxxxxxxxxxxxxxx> wrote:

On Fri, 8 Dec 2006 11:36:40 -0500, "Gus Chiggins"
<guschiggins@xxxxxxxxxx> wrote:

Hello all. I was directed here from the alt.guitar.effects group. What I
would like to do is wire an LED to a Roland FS-1 foot switch pedal. The
pedal switches between two channels on my guitar amp and I would like to put
an LED on it so I know when it's on a specific channel. Thanks in advance
for any help.

---
Post a schematic to alt.binaries.schematics.electronic or post it to
a web page somewhere and supply the link.

It's only gonna work (well) if it's switching DC voltage
rather than just re-channeling an audio signal.

IF it's switching voltage around then :

--> # <--
| | |--(Resistor)---(LED) ---
| | | |
| | | |
| | | |
o | o Gnd
u V+ u
t i t
1 n 2

This will light-up when "out2" is selected but be
dark when "out-1" is selected. If you get one of
those 2-color LEDs from Radio Shack you can hook
one leg to "out-1", the other to "out-2" and run
the ground leg to the ground wire through a single
resistor.

The value of the resistor depends on how much
voltage there is on "V+ in". For 5 volts DC the
resistor should be no less than 250 ohms, preferably
a standard 330 ohm. For 12 vdc, use a 660 ohm. The
idea is to get just below 20 milliamps going through
the LED (12/660)= 0.018 amps = 18 milliamps

If "V+in" is an *AC* voltage - especially 120 volts -
don't even THINK about using an LED unless you know
how to cope - better to use a 120v regular bulb or
neon light instead.

If an AUDIO signal goes through the switch, you might
get an LED to register *something* - but it will do
so by bleeding-off some power from your signal.

.

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