Turn on LED when plug is inserted.

[Sanguinicus]

Hello all. I'm building the RG Keen 'Spyder' power supply. At the 9V outputs, I'd like to have an LED light up when a plug is inserted in the 2.1mm jack. There was a previous thread about this same topic but I'm afraid I can't wrap my head around the methods that were explained. I'm after a diagram (not schematic) of how it could be connected; I don't understand how the switch works. Here's a really rough scribble I did in paint of how I think it should be done. It's not complete though, because I have no idea how to do it.

Any feedback would be great.

[slacker]

I haven't seen the original thread so I don't know if this was one of the methods discussed, but this will do what you want.



With nothing plugged in A and B are connected together so both have 9 volts on them, this means both sides of the LED have the same voltage so no current flows through it and it will be off. When a plug is inserted it disconnects B from A, B is now connected to nothing so current can flow through the LED and it turns on.

[Sanguinicus]

Thanks mate. This kind of looks like what I scribbled on an envelope in a moment of clarity about 5 minutes ago 

[slacker]

No problem, just saw the other thread and this is exactly what Alex suggested. To answer your last question from the other thread the LED will turn on when you insert the plug, doesn't matter if the other end is connected to anything or whether the pedal at the other end is on or off. It just shows you something is plugged in.