Question about wiring household outlet to 5v LEDs.

[InlineFive]

Originally posted by: yellowfiero
You don't need DC to run LEDs. They will run perfectly fine in AC, they just flicker very fast (like a flourescent tube).

Wiring 24 in series would be fine, but remember, as soon as one dies, the whole string dies with it (i.e. dies open circuit).

If these 5V LEDs have internal dropping resistors (5V types usually do, since the forward voltage drop for GaAs LEDs is about 2.2VDC), then current limiting would not be required.

I still would not recommend doing it this way, as the OP indicated he is a novice in wiring, and he would be playing with potentially lethal voltages.

Get a 6.3V filament transformer from RS, and do it that way. HTH

What does a transformer filament do? If it only provides a total of 6.2v that's not enough for a bunch of LEDs.

-Por

 

[DrPizza]

*YES* you can wire diodes to AC. They each have their own internal resistance, so 20 or so should do the trick just fine.

<--- physics teacher.

I have, for a classroom demonstration, wired 2 LED's to the end of an extension cord that I cut off - 2 different colors, 1 in each direction. When I plug the cord in, it looks orangeish, because one diode is yellow/green and the other is red. But, in a darkened room, when I spin the extension cord around in a circle above my head, students can clearly see that only one is on at a time (because of persistance of vision, it makes a circle of alternating arc segments of red and yellow light.)
Using the rate that I'm spinning the cord (so many revolutions in 10 seconds) along with the number of arc-segments seen in one complete circle, students can easily calculate that the electricity is 60 Hz with fairly good accuracy.

btw, I'd recommend shrink tubing (whatever it's called) for the exposed wires - it's quite easy to work with. It's like small innertube shaped stuff that you put over the bare wires... apply a little heat and it shrinks to make a nice covering. Also, I've touched live 110 many times... I have yet to win a Darwin award. I'd have to be standing in a puddle or grabbing the sink or something to have much of a chance for that to happen. Interestingly, there's a cool physics demonstration: Get a large beaker of distilled water - insert live wires into beaker - insert hand into beaker - nothing should happen. Personally, I don't have the guts to do that.

 

[dullard]

DrPizza, I always thought you were a math teacher.

Be careful that your diodes do have an internal resistance. I've been fiddleing with LEDs for a while at work (actually it is a coworker who is doing it and I've helped get him the electrical connections done). We blew out quite a few LEDs by hooking them directly up to the proper voltage power supply. We never knew that LEDs were current driven and not voltage driven (ie the voltage they require will vary over time). Thus you must look at your voltage and look at the LED current and hook up a resistor in series to limit that current so that it could never surpass the LED maximum current. Once we realized we needed resistors the LEDs stopped blowing. I think LEDs should be advertized by their current and not voltage since that makes it confusing to those of us who aren't educated in electronics.

These internal resistance LEDs sound interesting, I'll have to search for some.

 

[Anubis]

how about you tell us why you are doing this

 

[InlineFive]

Originally posted by: Anubis
how about you tell us why you are doing this

Neat lights for my bedroom.