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wiring up LED's for in-house use

Discussion in 'Electronic Basics' started by Jason, Nov 20, 2004.

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  1. Jason

    Jason Guest

    I'm looking for some direction here. I've come up with an idea for a
    home project. But don't know where..or exactly WHAT I need to get to
    make it happen.

    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. But routing
    a groove under the overhang on the stairs (these are hardwood stairs
    mind you) and putting an LED in each groove, I think it would light
    them up well enough and look pretty slick at teh same time.

    The problem is I'm not sure where or what I need to get to make it
    happen. The LED's and such are simple. But the power supply is what's
    giving me problems. Basically I want something safe and as low power
    as possible, only what's needed. I can't seem to find anything that
    looks to be more than a hobby/science project level device. I want
    something that I can just wrap my wires around and safely plug into an
    outlet somewhere.

    Can anyone lend some suggestions here? I would greatly appreciate it.
     
  2. 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
     
  3. peterken

    peterken Guest

    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
     
  4. Asking the OP? Or me?

    Jon
     
  5. Byron A Jeff

    Byron A Jeff Guest

    -
    --> On 19 Nov 2004 17:43:33 -0800, (Jason) wrote:
    ->
    -> >[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
     
  6. 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

    <http://www.goldmine-elec.com/default.htm>

    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.
     
  7. 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
     
  8. Rich Grise

    Rich Grise Guest

    Sure! Just work from the basement! ;-)

    My first thought was, if the OP isn't "stuck" on LEDs, what about those
    light strings like they use in movie theaters? A string of xmas lights
    could work in that app. Lead dress is always just an aesthetics problem. :)

    You could even use some of those outdoor low-voltage things, and junkyard
    car reverse/back-up light things, but now we're talking construction
    project. ;-)

    Good Luck!
    Rich
     
  9. Ray

    Ray Guest

    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.
     
  10. 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 ()
     
  11. Zack

    Zack Guest

    Why do you need to use the resisters?
     
  12. Lord Garth

    Lord Garth Guest

    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.
     
  13. Bill Bowden

    Bill Bowden Guest

    That sounds wrong to me - I say series!

    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
     
  14. Ray

    Ray Guest

    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.
     
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