Hooking up LED lamps to 12 volt source

[Norm]

 Some of my LED lamps use 6volts(4AA alkaline

batteries, some only require 2AA batteries for

each lamp now can I simply for example put 2 LED

lamps each requiring 6 volts in series to a 12

volt battery.....(Duh!) I know it might sound

dumb but I'd hate to ruin $16 worth of lamps

by doing it.

  Thanks for taking the time to answer this

anyone.

  Any reason for making your own set of lamps

just to save money....or is it mostly for the fun

of it?

            ( :>) Norm.

[wooferhound]

These links should be really useful for connecting LEDs to any voltage, and any number of LEDs in series.

http://www.otherpower.com/otherpower_lighting_leds.html

http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm

http://www.fieldlines.com/user/commanda/stories

[Capt Slog]

Very like the calculator that Woofer posted, but this is the one I use..

http://led.linear1.org/led.wiz

[Electron Skipper]

Actually a better solution to Norm's situation is to be found here:

http://www.zetex.com/3.0/appnotes/apps/an44.pdf

Downside is they are an SOT-23-5 configuration so sharpen your soldering iron tip.

Digikey actually carries the 2 items mentioned in the application note.

http://www.zetex.com/3.0/pdf/ZXSC300.pdf

http://www.zetex.com/3.0/pdf/ZXSC310.pdf

Are their datasheets, but the figure 3 circuit of the application note provides the means of lowering the supply voltage to the chips, and with efficiences better than 85% are well worth looking at.

[Electron Skipper]

I forgot to add that these are less than a buck each with price breaks at 25 units.

[commanda]

Any reason for making your own set of lamps

just to save money....or is it mostly for the fun

of it?

A 12 volt battery used in an RE situation, could be anywhere between 11 and 15 volts.

Online calculators are all well and good, but don't assume a 12 volt battery is 12.000 volts.

I wrote a mini-thesis on this subject a while back; the last part is here:

http://www.fieldlines.com/story/2007/10/31/848/94375

but has links to the first 4 parts.

I build all my own stuff on the theory that if I built it, I can fix it.

Generally speaking, lamps designed to run on AA batteries won't handle the much greater voltage range of a real RE situation.

Amanda