Thread: Blue LED question

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Does anyone have a guess of how long 2 blue LED's will burn off 1 9V battery before the battery dies?

A VERY long time.

I have the same set up for a skull. I took the skull camping this summer twice for long weekends (not me and the skull only....there were others about!). I have yet to replace the battery.

Last year I burned for 3-4 hours a night for about 14 nights on one battery running two red super bright leds.

Hope that helps!

A very, very long time.

Well...if they last anything like the pair of super-bright red LED's I've been testing in my ghost, they should remain bright for well over 100 hours...then they'll begin to dim...

I've had this pair running since the first week of October, and at this point, they're only visible in rather dark conditions - but they have been running CONSTANTLY since October 4th or 5th...
Oh...and that's with a bit of hot glue over them, to disperse the cone of light, which keeps them bright, but diffuses the light over a broader area...

I'll be replacing the battery and hanging the ghost this weekend...

thanks guys!

Just remember to use an appropriate resistor. It'll keep the LEDs from burning out (yes, this can actually be a concern, especially with the blue ones), and it'll prolong the battery run-time.

I have a page where I wrote out the equations, assuming you know the voltage of the LEDs (usually on the package if you got them from radio shack):

(Installing LEDs)

And also here's a web-calculator you can use, so you don't have to use any math.

(LED Calculator)