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btnhfan
12-17-2005, 10:38 AM
I was wondering if anyone knew of any leds to use for home. Im looking to get uv ones for a table.

The ones from oznium would work right?
You just have to wire them in series to get 120v right?

JimJ
12-17-2005, 01:26 PM
No different than wiring them for a car...except you'd probably need a wall-wart power supply as they aren't designed for AC.

btnhfan
12-18-2005, 08:51 PM
Really?

How bout any of these?
Or is it the same thing...

http://www.superbrightleds.com/leds.htm

thylantyr
12-18-2005, 10:21 PM
You would probably need to do this as a bare bones solution to making it work.

You insert a generic diode like 1N4003 and place it in series with the LED because
the LED reverse voltage is only rated for 5V. These 1N4003 are rated for 200V.

AC input -> 1N4003 -> LED -> resistor

Diagram 1
http://library.thinkquest.org/16497/projects/beginner/p3/led-diode.gif

The diode and LED have a polarity and notice how they have it wired.
Diode cathode to LED anode.

Replace the 3V battery in the circuit with 120v AC.

Last, recalculate the new resistor value for the increased voltage.

AC volts peak = 120v rms x 1.414 = ~ 170.

Figure out what the nominal LED current is to safely operate it. Lets use
0.02 amps.

The shortcut math that is 99% accurate is;

170v / 0.02 A = 8500 Ohm resistor.

Replace that 470 Ohm resistor in that drawing with one that is 8500 Ohm,
but this resistance value is not common so you can round up to 10,000 Ohm.

Since the AC mains are alternating, the LED will be turning off/on many times
per second. It may be doing this so fast that you may not notice it.

Diode specs;
http://www.fairchildsemi.com/ds/1N/1N4001.pdf

If you want to make a better circuit, there is more ways. This is the bare bones
method.

If you have more than one LED then you insert them in series and because there is
a small voltage drop across each LED and diode, eventually you will have to redo the math
to get an appropriate resistor so you don't get severe dimming.

btnhfan
12-19-2005, 12:36 AM
Hmmm

So i need a diode for each led?

req
12-19-2005, 01:42 AM
if you scoop one of these
http://www.allelectronics.com/matrix/DC_Wall_Transformers.html

6 Vdc 1.5 amp 2.5mm co-ax positive C DCTX-615 4.25 3.25

you can hook 2 led's together [in series iirc?] each time for 3v each, and then wire each group of 2 leds in parallel off the power transformer (lop the end off) and since your LED's pull just about 20ma each - you can hook just around 75 of them to each transformer :)

that way you dont need any resistors, and they are well under their 3~3.5v limit. throw a potentiometer on there and you got yourself a dimming switch! :D

and then just run them whereever ya want. get a little toggle switch to put inline on the - wire and your all set.

hope that helps.


also

http://www.lsdiodes.com has the BEST leds on the planet. period.

btnhfan
12-19-2005, 02:56 AM
Awesome.


I think thats what I will do.

Just gotta work on my soldering skills now.

thylantyr
12-19-2005, 11:14 AM
Hmmm

So i need a diode for each led?

You only need one diode per loop. If you have 1 LED or 100 in series, one diode
is fine. The real question is.. Why do you need to operate the LED's from a 120 volt AC source? The AC/DC adapter method is more politically correct.

btnhfan
12-19-2005, 12:05 PM
Yea thats what Im doing now.

Realized that.

req
12-19-2005, 11:38 PM
yay!

i win thylantyr!!! :D

i beat you! MAUAHHAHAH!!! :2thumbs: