Wiring up LED with 3PDT

[shredaholic]

I'm going for true bypass switching on my MXR Flanger clone, and have an ultrabright green LED and 3PDT switch for it. On some diagrams, before the positive lug of the LED there is a 1k or 1k5 resistor - is this necessary, and what's it for?

 

[DWVINKY]

Re: Wiring up LED with 3PDT

That resistor is for current limiting. If it wasn't there, the LED would be real bright for about two seconds, and then it would open up.

 

[shredaholic]

Re: Wiring up LED with 3PDT

Thanks! I thought it might be to do with the current going in.

 

[ErikH]

Re: Wiring up LED with 3PDT

The brighter the LED, the more current draw from the battery. The rule of them I go by with the limiting resistor is start with 10K and adjust from there to taste depending on how bright you want it. 10K seems to be good because the draw is minimal from the LED yet still bright enough to see it. Ultrabrights usually need a larger value.

 

[shredaholic]

Re: Wiring up LED with 3PDT

The thing is, itll be powered by a 240>9v adaptor, so I guess all I'll have to worry about is not using too many pedals from the same source.

 

[ErikH]

Re: Wiring up LED with 3PDT

Yeah, just watch the current draw from all the pedals, but that LED will be in that equation as well. The bigger the limiting resistor (dimmer the LED) the more mA's available for the other pedals.