LED Flashlight and Battery Configuration

[BeachDude]

If I'm going to create a LED flashlight, and the majority of my LEDs
have a forward voltage of 3.5volts - which battery setup should I
choose?

1. ONE single 9volt battery connected to all my LEDS (in parallel)
with a resistor ahead of each LED.

or

2. THREE 1.2volt rechargeable AA battiers connected end to end until
the voltage is within the LEDs voltage needs. All the LEDS would
still be in parallel - however since the supplied voltage is more
closely matched to the LEDs, I probally wouldn't need much of a
resistor.

Is it better to get a voltage thats closer to the LEDs and use smaller
resistors, or is the convienence of a 9volt battery better? One
9volt sure beats a bunch of AA's. Then again, several AA batteries
sound like they would last longer collectivly than one single 9volt???

How much of my 9volt's capacity is wasted with the resistor (heat)
that could be used to power the LEDS? Should I even worry about
lost power thru the resistor??

Is there another way I've not considered? Basically I want to run my
LEDs in Parallel and have my batteries used to their full potential,
wasting the least amount of their capacity via heat.

Any suggestions?

 

[dan]

What's that Lassie? You say that BeachDude fell down the old
sci.electronics.basics mine and will die if we don't mount a rescue by
27 Jul 2004 19:29:04 -0700:

If I'm going to create a LED flashlight, and the majority of my LEDs
have a forward voltage of 3.5volts - which battery setup should I
choose?

1. ONE single 9volt battery connected to all my LEDS (in parallel)
with a resistor ahead of each LED.

or

2. THREE 1.2volt rechargeable AA battiers connected end to end until
the voltage is within the LEDs voltage needs. All the LEDS would
still be in parallel - however since the supplied voltage is more
closely matched to the LEDs, I probally wouldn't need much of a
resistor.

Is it better to get a voltage thats closer to the LEDs and use smaller
resistors, or is the convienence of a 9volt battery better? One
9volt sure beats a bunch of AA's. Then again, several AA batteries
sound like they would last longer collectivly than one single 9volt???

How much of my 9volt's capacity is wasted with the resistor (heat)
that could be used to power the LEDS? Should I even worry about
lost power thru the resistor??

Is there another way I've not considered? Basically I want to run my
LEDs in Parallel and have my batteries used to their full potential,
wasting the least amount of their capacity via heat.

Any suggestions?

just one

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