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Help needed... Toggle switch for LED lighting circuit

Discussion in 'Electronic Basics' started by Chris, Feb 18, 2006.

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  1. Chris

    Chris Guest

    Hi, Lee. You're going to have some difficulty with switch bounce, and
    also with people changing their minds, more than one person going down
    the stairs, and lots of other things. It's not going to be pretty when
    Grandma steps on the first stair, and your gizmo turns itself off.

    It might be better for you to set this up with a timer, so the LEDs
    will go on when someone steps on either step, delays on for a minute or
    two, and then goes out. Things are complicated a little by the total
    current you're switching (about an amp).

    There are many kits available that will give you an intermediate time
    delay. The Velleman K2579 is a good choice -- it will give you a
    consistent time delay of 0 to 15 minutes. It's based on the venerable
    LM555, and is a proven circuit with a circuit board and easy
    instructions. Once you build the kit, you can just wire your two
    pressure switches in parallel between the SW1 and the - of the power
    supply, where either one could initiate the delay. The 555 drives a
    relay that can switch 2 amps. Check it out before you buy:

    It's available from many hobbyist sources for around $15. And if the
    trip to the store or the minimal cost doesn't appeal, just make one
    yourself out of components from your junkbox.

    Good luck
  2. John Fields

    John Fields Guest

  3. JazzMan

    JazzMan Guest

    Probably not a bad idea to use an off timer too incase the
    presure plate gets missed on exit, otherwise the next user
    will turn the lights off when they hit the plate. Or,
    if you have a metal hand rail you could use a touch sensor
    in the rail to trigger the lights, or use an infrared motion
    sensor as is to trigger the lights. The motion sensor can
    be hidden in the tread face board or in an overhead fixture.

    Please reply to jsavage"at"
    Curse those darned bulk e-mailers!
    "Rats and roaches live by competition under the laws of
    supply and demand. It is the privilege of human beings to
    live under the laws of justice and mercy." - Wendell Berry
  4. ehsjr

    ehsjr Guest

    Dump the toggle idea and use PIR to sense when someone
    is on the staircase. Toggle is too easily defeated by
    human unpredictability.

  5. Bob Monsen

    Bob Monsen Guest

    Do you have the pressure mats already? If not, a cheaper alternative might
    be a sharp IR sensor, like a GP2D12. Mount it facing across the step,
    and you'll be able to get a voltage pulse when somebody steps on the stair.

    The timer idea some people have been suggesting is nice, except that if
    people decide to sit on the steps for any length of time, the lights will
    go out. Also, the LEDs on the top steps will be visible for people on the
    lower steps unless you shield them somehow.

    I have a dark hallway leading to a bathroom and a coat closet. The hallway
    has a light, but there is no switch for it; it uses a twist switch on the
    lamp itself. So, in order to find the bathroom at night, you had to feel
    around to the lamp. Sadly, the lamp had a glass shield that popped out if
    you pushed on it. So, the only real solution was to leave the light on all
    the time, which I disliked for various reasons. So, I used one of those IR
    sensors to sense when somebody was coming up the hallway, so I could turn
    on the light for 5 minutes, on a timer. There are several issues I have
    with the current circuit, though. There is no way to simply turn on the
    light and leave it on (no external switch). There is no way to adjust the
    length of time (without reprogramming the microcontroller that is used to
    time the delay). Also, the light flashes on unexpectedly for newcomers,
    which can be startling, since it is hard to see, and if you happen to be
    looking in the wrong direction, can be blinding. FYI. These are all easy
    to solve problems, but I haven't gotten around to fixing them yet (it has
    been a couple of years now... I post this as food for thought.

    Bob Monsen

    I know not with what weapons World War III will be fought, but World
    War IV will be fought with sticks and stones.
    Albert Einstein
  6. Rich Grise

    Rich Grise Guest

    Or one of those PIR yard lights - I think the turn-off delay is adjustable.

    Or, just turn it on whenever somebody steps on either of the mats, and
    leave it on for, say, 3-5x the time it normally takes to go up or down
    the stairs.

    Or, just leave the suckers on whenever it's dark inside. :) (like
    those photoelectric night lights.)

    Good Luck!
  7. cbm5

    cbm5 Guest

    Your idea does not account for multiple people on the stairs.
  8. Chris

    Chris Guest

    Hi, Lee. You've got quite a few good ideas from other posts. If you
    decide to go with the Velleman kit, though, you might just want to make
    a small addition when you install the circuit. Looking at the manual
    for the kit, it seems the switch is just tied directly to the 555 TRIG
    pin (turns on the 555 when grounded), with only a 1K pullup resistor on
    board. If you actually install that circuit, electrical noise may
    cause false triggering of the 555, leading to "nuisance ONs".

    You can pretty much get rid of that by adding two components, commonly
    available at Radio Shack or any hobbyist outlet, by tack-soldering them
    on the circuit board as shown (view in fixed font or M$ Notepad):

    | VCC
    | +
    | | Internal
    | .-. 1K Ohm
    | | | Pullup
    | | |
    | 22 Ohm SW1 '-'
    | FSW1 FSW2 ___ | To 555
    | .------o-----------|___|-o-------o--o---o-> TRIG
    | | | | Pin
    | | | --- .---o--o----.
    | \ o \ o ,01uF --- | |
    | \ \ | | |
    | \. \. .------------o---' ===
    | o o | GND
    | | | |
    | | | |
    | '------o----'
    (created by AACircuit v1.28.5 beta 02/06/05

    The .01uF cap and the 22 ohm resistor together will help prevent false
    triggering, and the 22 ohm series resistor will also help extend the
    life of the floorswitches FSW1 and FSW2.

    Good luck with your project. Have fun!
  9. nibbles

    nibbles Guest

    Hi all,

    I'm trying to create an LED lighting system for my staircase - which will
    have a row of 15 LEDs under each tread bullnose, that are switched on/off by
    pressure mats located at both top and bottom of the staircase.
    I intend to wire up the LEDs as 65 parallel arrays of 3 LEDs operating on
    12v @15ma/3.5v using a 100 ohm resistor for each (195 in total so lots of
    soldering to be done!).
    The above was calculated using the this online calculator so if my description isn't clear, pop them
    details into the calc' for a diagram.

    What I need help with is a simple(ish) diagram to operate the toggle
    function as mentioned above, eg; Switch on when someone steps on the bottom
    pad and off when they step on the top pad - or vice-versa.

    Any suggestions would be greatly appreciated.

  10. nibbles

    nibbles Guest

    Chris, you're an absolute star!

    A timer setup was my first option in mind, but I thought it would be neater
    to have the light switced off by the user too, I was thinking that there
    must be some way of crating a toggle circuit that could only be switched
    on/off by the opposite switch... But hey, the timer idea is probably more
    functional and easier to implement.
    Also those Velleman kits are great and well within my scope of understanding

    Thanks again
  11. nibbles

    nibbles Guest

    Thanks everyone for all the ideas, theres a few that I hadn't considered
    there - I especially like the idea of the touch sensor in the hand rail as I
    will be fitting a stainless steel rail soon.
    Any ideas on setting such a system up, coupled with the off timer?
  12. Jasen Betts

    Jasen Betts Guest

    SPDT is a fairly simple switch, a bedlamp switch won't do it,
    but many others will.
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