"Wayne.B" wrote in message
...
On 29 Dec 2005 17:47:55 -0800, "
wrote:

If I remember
right, it was less than 1/2 of a 12 watt bulb. I am speccing 1 watt
resistors for it though (6 resistors in parallel each in series with an
LED).

=========================================

How many LEDs in series would it take to use no resistors at all?

Six 1 watt resistors per LED sounds like a lot of wasted power to me.


1 watt resistor can dissipate 1 watt of power across it, does not mean there
will be that much power. We always used 1/4w resisters.

OK, my recollection from a web site about LED use said to figure a
voltage drop of 3.4 volts for the white ultrabrights leaving about a 9
volt drop for the resistor. At 600 ohms, this gives about .015 amp
through each resistor and LED. Yes, the correct resistor wattage is
less than 1/4 watt but I hate blowing resistorswhen odd things happen
and space saving is not a consideration here. Radio Shack had nothing
even as alrge as 1/4 watt less than 1000 ohms.

wrote in message
oups.com...
OK, my recollection from a web site about LED use said to figure a
voltage drop of 3.4 volts for the white ultrabrights leaving about a 9
volt drop for the resistor. At 600 ohms, this gives about .015 amp
through each resistor and LED. Yes, the correct resistor wattage is
less than 1/4 watt but I hate blowing resistorswhen odd things happen
and space saving is not a consideration here. Radio Shack had nothing
even as alrge as 1/4 watt less than 1000 ohms.

That's what I really dislike about the "new" Radio Shack. I suspect once
their inventory of discrete components are gone, you won't be able to buy
*any* resistors, capacitors or anything there.

Eisboch

wrote:
OK, my recollection from a web site about LED use said to figure a
voltage drop of 3.4 volts for the white ultrabrights leaving about a 9
volt drop for the resistor. At 600 ohms, this gives about .015 amp
through each resistor and LED. Yes, the correct resistor wattage is
less than 1/4 watt but I hate blowing resistorswhen odd things happen
and space saving is not a consideration here. Radio Shack had nothing
even as alrge as 1/4 watt less than 1000 ohms.


It'd be more efficient to put 2 or 3 LED's in series with one resistor
so more of the power goes to lumens rather than heating resistors.

-rick-