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bob golding:
hi ghurd,

i reckon 350 mA divided by 18 comes out at 19.5mA per led. cant see were you get 55 mA from? they dont seem to be running hot. the resistors  get warm but thats because they are 1/8 watt ones i just had kicking about. think i wil get some of those 12 volt compacts from the dans if my cold cathodes dont do the job. played with my 6 peltiers today. they are giving out about 15 watts just sitting on the stove with a heatsink sitting on top. very pleased with them,looking forward to rigging them up properly with fans and clamping them tightly. fans draw 2 watts each so  should  still have about 10 or 12 watts to play with hopefully.
cheers

bob

ghurd:
For 12 volts, wire 3 LEDs in series.  For 18 LEDs, that's 6 strings of 3 LEDs.

Just 1 resistor per string. 20ma per string.


strings at 20ma is 120ma.  Same ma to each LED, so same brightness.
ma goes down to 120ma.  Saves 2/3 of the power.


Wasted power in your resistors is about 4 times what it would be wired this way, so the resistors won't get warm either.
Glad to hear about the peltiers.  Thats on the list when the money gets better. I would love to see some numbers for that!  I have a couple ideas to do away with the fan. To compicated to explain, but easy to do.
For the fan, How about a 5v 150ma laptop fan? Moves some air, low corrent, run it direct from 1 additional electricialy seperate peltier? Maybe even 2 from a single peltier?
G-

tawa:
Whoa, wait a minute. Are you saying that peltiers give off electricity if you apply heat? I thought only special prototype chips did that? (Aren't peltier plates the ones that have one cold and one hot side if you apply electricity?)

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