Hey guys, I'd like to add a green LED to the pickguard when the guitar is "on". I'm installing a killswitch (mini switch), when it's in the "on" position I'd like a green LED to come on. I know I have to use resistors but I don't know the voltage of the current coming in from the amp. If I know the voltage, I should be able to google the right resistor, correct?

Any help you guys can provide?
There's an example of the wiring you need in one of the first few posts in the wiring thread
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Quote by obeythepenguin
Damn, that was fast. AlexW1989, thanks to you I can finally get to sleep again at night...
2P2T switch.
one side used for killswitching, the other for the led's.
however, you will need a 9v and the right resistors/leds, or the leds will burn out, ect.

but its defenatly doable.
Quote by Scowmoo

You deserved this, Matt.
current coming in from the amp?

use a 4.7k resistor, limits the current to about 50mA, so it burn out your LED
you might want to wire it so the LED comes on when the guitar comes off... the LED will be on a lot less, and it'll save batteries
^ why the hell would you want a 4.7k resistor? 300-400 ohms is usually closer to the right value for a standard LED.

lets just take the first green led on smallbear, kingbright L53GD. pull up the spec sheet and see the typical forward drop is 2.2V at 20mA. take our 9V and subtract 2.2 to get the voltage overthe resistor (6.8V). divide the voltage by the current and we come up with 340 ohms. id probably go with a bit higher to limit the current a bit more, but anything around there works.

how to wire it up, well that depends on if you want the LED to automaticly turn off when you remove your cord from the guitar. simple to do, just takes a few inches of extra wire. just have your DPDT switch, 390 ohm resistor, green LED, a stereo jack and some wire.
No current is coming in from the amp at all. For an LED, you're going to have to use a battery.
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& if you use the right battery (ie 1.5V), then you'll not not a current limit resistor (though you'll need to have a test run with your LED to see if it'll be bright enough for you)
Last edited by HankMcSpank at Jan 10, 2010,