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Power for 12 LED?

I want to make something and decorated with LED lighting for my girlfriend's birthday present.

I will need to light up 12 LED, which has typical forward voltage around 3.5V, and I wonder what is minimum number of batteries (AA/AAA) I need to use and will still give a reasonable brightness please?
Can it be less than 3 batteries? As it doesn't really make sense to have a lot of batteries in a small present.

Thank you very much 

omnibot6 years ago
Yes, It can be done with 3 batteries or less with a joule-thief.
I often use these simple circuits to drive lots of LEDs. By winding on really small thoroids I've upgraded my headlamps and flashlights. I use 10-100kOhm potentiometers (variable resistors) in place of the usual 1k resistor to make them more flexible.
Re-design7 years ago
You might do it with 4 batts.  It depends on what the currant usage is .

Go here and fiddle around.