wiring up LED's for in-house use

Just a thought, but would a simple, tiny box with a push button and a bright, white LED at the top and bottom of the stairs (set on the wall like a light switch) be enough? I'm thinking of a timed circuit that would turn on the LED only for a short time and use one AA or AAA battery. Some of those LEDs are pretty bright and could be aimed appropriately from the wall. If the timing was set to, say 1 minute, then it may meet your needs without routing, wiring, etc. Less time and money.

Unless you really just have to have the under-stair look, here.

Jon

bright,

light

LED

are

timing was

etc.

Ever thought of putting the leds in series and using an ordinary transformer like say 220-24V at say 100mA ? Or even a simple wall-warth accomodating the needed voltage ?

P

Asking the OP? Or me?

Jon

-

-> ->

-> >[SNIP]

-> >In our house we have two sets of stairs that are very dark. Even with

-> >the hallway lights on above them, it's still so dark that you can't

-> >see walking down them. I want to use LED's to light them.

-

-Ever thought of putting the leds in series and using an ordinary transformer

-like say 220-24V at say 100mA ?

Why use an ordinary transformer when a wall wart will do just fine. Find a

9-12V DC @ 500ma and go to town.

I'd suggest using a resistor per LED and wire in parallel. So if one LED goes out for any reason, the others still function.

-Or even a simple wall-warth accomodating the needed voltage ?

That's the right idea. Now the problem is reduced to how to get the power to the stairs.

BAJ

Buy a 'wall wart' from radio shack or wallmart that supplies 5VDC at 500mA.

Run a pair of wires down the stairway. Connect one of the wires to the positive output, and the other to the negative output of the wall wart. Wall warts generally use those little 'coax' plugs. You can buy coax sockets at radio shack, or just cut the wires coming out of the wall wart, and connect them to the wires running down the stairs.

Do not connect the wires to each other anywhere, and make sure they won't touch each other (that would be a 'short circuit').

At each step, connect the positive wire to a single 100 ohm resistor, then to the long lead of to a white LED. From the other lead of the LED, run a wire back to the negative wire.

Test the circuit, and make sure the wire isn't getting warm near the wall wart. If you use lamp wire, you shouldn't be able to feel it warm up. Speaker wire might be OK too. Generally, wire about the same size as the wire coming out of the wall-wart will be OK.

You can buy all the parts online at

or just buy the parts at radio shack.

--
Regards,
   Robert Monsen

"Your Highness, I have no need of this hypothesis."
     - Pierre Laplace (1749-1827), to Napoleon,
        on why his works on celestial mechanics make no mention of God.

All these will work, of course. But if it were me outfitting a stairs to make them safer to walk up or down, I'd probably rather avoid stringing wire, attaching it so that it is relatively permanent and safe as well as reasonably attractive, protecting the wiring from scuffs and cats and kids and so on, routing the edges of stairs, and having to find a nearby outlet. Etc.

Which is why I was curious if a different arrangement would solve the problem, satisfactorily.

Jon

I just got 50 11000mcd white LED's from E-bay for $12, the run on 3.5V

30mA. As Robert said, wire LED's in parallel with a 100ohm resister to each diode. They will only pull about 15mA each if you power with a cheap 5v wall adapter or an old computer power supply. If you used all 50 diodes you would only be pulling about 750mA. Something else to think about is alternate ways of turning it on... get a couple IR sensor and IR diode at the top and bottom of the stairs and when someone breaks the beam, a timer circuit (555) will turn the diodes on for a minute or so.

Why do you need to use the resisters?

That sounds wrong to me - I say series!

Not far from true! And the total light output would be anywhere from "7 watt nightlight" to something higher but probably less than that of a 15 watt lightbulb! And please note that 120 VAC 15 watt lightbulbs have half or a little less than half the efficiency of 100 watt ones!

- Don Klipstein ( snipped-for-privacy@misty.com)

It limits the current to a safe level. Without this, the LED would burn up. The limiting in those little key chain lights is the internal resistance of the button cells.

Well, you can't put 50 in series, but you might use

2 strings of 25 which only requires 2 resistors and a 200 volt bridge rectifier. 25 in series at 3.5 each is 88 volts. The peak line is 170 so you have 82 peak across the resistor. RMS of 82 is 58 so the resistor will be 2900 ohms for 20 mA RMS current. A 2 watt size should handle it.

-Bill

Have you gave a thought to having them on the ceiling pointing down? Then you could put them in some type of track u shaped, have the wires tucked inside and just nail or staple the track to the ceiling. No trip wires or chew toys for animals. It'll be like party lights going up the steps. Have your power coming off the light fixture so the existing switch will turn on everything. Wire up some white christmas tree lights to see if you like the idea before making a bunch of series/parallel cables.

--
-Ray