LEDs and Battery Drain

[zeppman]

Hey guys-

What is the difference in battery life between a dpdt circuit with no status LED and a 3pdt circuit with status LED?

Oh...and I finally got my compuRoss to work!!  It was a bad transistor after all...hours of frustration for a transistor.  But it sounds great!  I plan on building another..but with 1% resistors, an LED (if it doesn't suck current) and an attack switch.  Thanks for everyone's help

[brett]

RG Keen's Milleniums don't suck any significant power except to light the LED.  A 2.4k resistor reduces the current to 3mA, making a typical 9V battery last a longggggg time.   With a high-brightness LED you might even get away with a larger value resistor and less current.  Best of all, buy a wall-wart and forget batteries  :wink:

cheers

[KORGULL]

Depends on how bright you make the LED. Use a high value resistor in series with the LED to limit current consumpton. Make the LED as dim as you can stand it.
I've read that in many circuits the LED indicator consumes more current than the actual effect circuit.

[Mark Hammer]

LEDs are rated in terms of millicandles with respect to brightness.  Traditional  red LEDs tend to be in the 250mcd and under range.  High brightness LEDs can often be in the 2000mcd and up range.  One of the nice things about these LEDs is that while they are capable of being very bright with the same amount of current as the older types, they are capable of being equally bright with substantially LESS current.  I can easily get away with an 18k current limiting resistor (compared to those in the 2k2 and under range) using a superbright LED.

What is "bright enough"?  Depends on a number of factors.  plastic domes that diffuse the light tend to be more easily visible than clear domes that let you see the anode and cathode until the light starts to get realy intense.  You can make the clear plastic types more diffuse with a small piece of emery cloth or steel wool to buff the surface.  I also find that LEDs appear brighter against dark surfaces and surrounds.  So, use one of those black plastic collets, or heck just *paint* a black "bull's eye" around where you install the LED, and use a darker colour of paint for the chassis.  Of course, the down side is that black lettering doesn't look very visible against darker colours.

In general, whatever you can do to increase the contrast between the LED and its surroundings will let you get away with larger value current-limiting resistors, helping to reduce current drain and increasing battery life.  Most certainly, avoid use of separate LEDs for on vs off status.

[Mike Burgundy]

I use ultra-brights (2kCd and up) and a 4k7 resistor (!), 10k(!!) and 22k (!!!) or even more (!!!!) and still get results that are a bit on the bright side - brighter than my commercial pedals anyway.
I take a file to the LED to roughen up the surface enough to diffuse the light so it's visible from all sides - these ultra-brights tend to have a pretty serious focus. Works a treat.
If you use really, really bright LEDs you can get away with *really* low currents. I already managed to get one setup in which my meter couldn't distinguish between effect off (but powered) or effect on - with LED. What I do with these (if I bother to get them *just* right) is I first get them just as bright as your standard commercial pedal, and then give 'em a rather big tad more - ever play outdoors? This still leaves them very lean currentwise, though.

[zeppman]

so where do I get very low current LEDs... I just want something to indicate an on off status.  What color is draws the least current?

[STOMPmole]

They have a great selection at http://www.lsdiodes.com/.  Smallbear also sells super-bright LEDs.