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Discussion in 'Electronic Components' started by voodoochile, Jul 21, 2006.

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  1. voodoochile

    voodoochile Guest

    Hi guys,

    I wonder if anyone can help me with this simple problem I have as art of my
    school project..

    I am trying to turn an electrical current on and off down a wire via a
    wireless signal on a key fob.

    The cable is connected to a light. All I need to do is switch it on and
    off -remotely.
    Yes, I have seen remote light dimmers, but all I need to do is switch the
    light on and off (not dim) and make the circuit as cheap and easy as

    Can anyone tell me what the simple circuit diagram should look like, and
    what components need to be on the pcb etc?

    Plus if anyone can - what the circuit in the key fob should look like.
  2. JeffM

    JeffM Guest

  3. If you can't do it already, how do you justify your insistence that it is

    Does it have to be secure from misfiring from other sources of signals?
    Does it have to work round corners or through walls, or are you ok with

    And JeffM, you're a moron, I have some sympathy with your reason for
    posting but all you seem to do is show up like a dumb policeman. Some
    things are worth it, like that apparently deliberate attenpt to infect
    people with Redlof virus in that other post, but if you're going to slap a
    newcomer in the face you might at least offer something contructive and on
    topic. You didn't even suggest he might cross-post instead of multipost,
    let alone have something to say about his subject.
  4. voodoochile

    voodoochile Guest

    Thanks for the support.

    Yes the device is okay with line of sight.
  5. We need more details, what voltage, what current, and (as 'lost'
    pointed out) how robust it needs to be.

    It sounds like this is something you have to build yourself, is that
    true? If not, there are lots of car alarm systems with keyfobs, and
    Radio Shack used to sell X-10 switches with small (RF) remotes.

    Lots of ideas come to mind, 40KHz IR remote receivers, photocells,
    etc, but I cna't tell from here how applicable any of them are.
  6. Hey, didn't you just say that in some other newsgroup?
  7. Eeyore

    Eeyore Guest

    Yes - he went and multi-posted his msg.

    Ironic really.

  8. Ok I'll make the starting assumption that this is an educational thing to
    be a proof of concept, so the simplest possible answer is ok, you can see
    its weaknesses and move to better ideas from there.

    (Btw, if you reply like this, below the quoted text, it's clearer. Unlike
    email, many people might answer, so this way it's clearer to read from top

    If you're switching a light, you can maybe get away with using light itself
    as a switch if the main light does not flood your sensor. The keyfob in
    this case need have nothing but a baterry, a switch, a resitor and an LED
    chosen for narrow viewing angle and high brightness. The sensor would be a
    phototransistor (to save you needing another transistor as a gain stage)
    with a coloured filter over the front to match the wavelength of your LED.
    The phototransistor output would trigger a bistable circuit to latch the
    off/on state, and output to a triac to control the lamp current. (That's
    assuming it's mains current you're switching, which could be a wrong
    assumption for a basic educational project, but never mind..)

    Once you look for better ideas you'll want a pulse coded signal to
    eliminate false trigerring, or radio to allow indirect signal paths. Either
    of these are best handled with dedicated IC's, and I have no idea if this
    is permissible in your project. If it's required that you fully understand
    the logic and the part's behaviour, you might be better sticking to designs
    that use discrete components not IC's. If you figure out a neat way
    yourself, you'll learn more and probably get better grades from examiners,
    so long as you don't overlook standard methods already available to you.
  9. Aka: A Flashlight. 8*)
  10. Yep :) They even make those in keyfobs, is what made me think of it.. Very
    nice simple idea. Does need the narrow beam though, and the narrowband
    light. That way you can use the intensity of the narrow waveband and a
    suitable colur filter to displace some of the difficulty of making filters
    in electronics. The main problem is that you'd need a very narrowband
    dichroic filter to make the simple idea effective beyond proof of concept,
    and that's costly, and more about optics than electronics.

  11. No, he MULTI-REPLIED. There is a subtle difference.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  12. Don Bowey

    Don Bowey Guest

    How subtle is it when the reply as actually a new original post?
  13. Actually, he is replying to the existing post, the reference line
    does list the original message ID.

    But, he doesn't keep the original subject in the header, so it
    can look like he's starting new threads. I find that annoying, at
    the very least because it's not immediately clear which post he
    is replying to. I thought the proper way of doing it was to
    put in a new subject, but include the old, such as
    Spam (was: newbie question)
    or something to that effect.

    Then one knows the original thread just by looking at the subject
    header, and it's clear he is making a point about the original post
    rather than just posting nonsense (that it can look like to those
    who are unaware of what he's doing). I think it's also clearer about
    what's gong on. Announcing that something is spam or shouldn't be
    cross-posted, well it's too late for the original post. But it
    might help the newcomers, at least the ones who actually read
    the newsgroups before posting, because then they'd learn that
    such practices are at the very least frowned upon. Otherwise,
    it's too easy for them to take the bad practices of some as example.

    If someone wants to punish the original poster, then it can all
    be done simply by reporting him. The point of making it public
    is to try to limit further practice by others, and I don't think
    the removal of the original subject from the reply helps
    this process.

    He's also be in a far better position when he's announcing
    spam if he included a link to Mark Zenier's guide to the hierarchy,
    because that well explains where ads are supposed to go.

  14. Don Bowey

    Don Bowey Guest

    Good thoughts, thanks.

    But S.E.D should be S.E.D.P.HP, where P= Politics, and HP= Horse Puckey.

  15. Eeyore

    Eeyore Guest

    What's horse puckey ?

  16. Don Bowey

    Don Bowey Guest

    To get all the valuable nuances of the term, you should watch some of the
    "MASH" TV series. It appears to be an old military expression.
  17. JeffM

    JeffM Guest

    The point of making it public is to try to limit further practice by others
    Valid point. My thinking that everyone views in a threaded manner
    is a dangerous assumption.
    I guess there are also some newsreaders
    that don't keep threads together when the Subject line changes.
    (The original Google Groups was notorious for that.)
  18. Eeyore

    Eeyore Guest

    I've seen quite a number of those but don't recall the term.

    Over here we do however sometimes talk about ppl talking 'horse manure' - similar

  19. Don Bowey

    Don Bowey Guest

    Yes, that's it.

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