High brightness led: lowering consumption to preserve battery life?

[neurino]

I have a dumb question: I'm building a battery operated true bypass looper that will have 3 leds.

I have only hi-brite ones (~18/20mA each) available coming with their own 9V resistor.

I was thinking about placing a single res, adjusting to taste, to limit consumption and preserve battery life like this:



Will it work evenly on the 3 leds, independently from switches?

Will battery life be improved?

Or will it be better to double/triple each led resistor value?

[theehman]

Each LED having it's own resistor is definitely the best way to go if they're being switched on/off.

I always use a 1K5 resistor on my LEDs.  That runs the current down to about 5mA and it's still plenty bright without being blinding.  Try breadboarding the LEDs with different values of resistors till you find the largest resistor that will still allow the brightness you want.

[neurino]

Thanks, I was trying to be grasping in parts count 

[davent]

I regularly run the high brightness LED's at well below 1ma and they are still plenty bright, but test like said earlier to find what's enough brightness to meet your needs. I put a 1k resistor in series with a 10k-25k pot to test for brightness then replace the combo with a single resistor of the determined value. (The 1k prevents shorting out your led while testing.)

dave

[PRR]

> a single res

Shared resistor, the more lights are on, the dimmer each one is.

Generally you want 3 lights to be significantly "more" than 1 light, so you don't have to see and count.

> hi-brite ones (~18/20mA each)

IMHO, you do not want to run LEDs (specially hi-brit) at 20mA on most stages. As Dave says, 1mA is often ample; and 20X the battery life.

> grasping in parts count

No added parts; just right-size the ones you have:



> coming with their own 9V resistor.

Ah. Wrong part. No matter, add a few K ohms in series with each one.

[neurino]

Thank you guys, I'll go adding resistors in series to each led, maybe testing on breadboard first.

[DavenPaget]

Thank you guys, I'll go adding resistors in series to each led, maybe testing on breadboard first.

Yep , parallel resistors bog down the whole chain and is quite dangerous , since if 1 LED blows , other parallel LED's have to take the lost load , the point is , the Voltage is kept down by the Current usage over Resistance .
I don't how to categorize it under , whether as increased voltage failure or cascade failure .