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Problem, Solution = gerbils??

Discussion in 'Electronic Design' started by Randy Day, Jul 12, 2004.

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  1. Alan

    Alan Guest

    What about strapping a Gerbil to the fan? Works for both types of
    sensors :)


    Jenal Communications
    Manufacturers and Suppliers of HF Selcall
    P O Box 1108, Morley, WA, 6943
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  2. Clint Sharp

    Clint Sharp Guest

    How 'bout something like a Scalextric with a filament bulb mounted on
    each car's roof. Not only do you fool the sensor, you can have fun at
    the same time.
  3. I suggest trying a single automotive tail-lamp bulb modulated at 2-3Hz
    (555 + MOSFET driver). You don't really need to simulate motion with
    the pyroelectric sensors- in fact they have to turn motion of the
    target into an AC signal with their Fresnel lens.

    Best regards,
    Spehro Pefhany
  4. Well, thank you for that information. The usual new bldg has these
    sensors installed by the electricians, and then all the instructions are
    discarded along with the leftover packaging, so absolutely *no* one has
    a clue as to how these work and what to do with them. Isn't that
    crazily amazing..
  5. Now that takes some chutzpa. Using the PIR excuse for playing around
    with toys. But, yeah, that's a good idea. Gotta figure out how to
    power the light bulb, tho.
  6. I've got an IRF630 and a 2SK2135(?) laying around, maybe I'll make up a
    power flasher. I guess a 555 isn't really needed, just a flip-flop. I
    don't need full brightness, so I guess 6 to 9V would be enough supply V,
    assuming that the FETs will turn on enough at that voltage. The bulb
    should last about forever. Maybe a wall wart would handle the power.
    I might connect two lamps in series to get lower brightness.
  7. That was actually what I was thinking. Note to self: Be clear in solution
    definitions lol

  8. Duct tape a gerbil to the pendulum. Just be careful that you don't order
    the duct tape and gerbils from the same outlet, or you'll end up on
    someone's watch list. ;-)
  9. PaulCsouls

    PaulCsouls Guest

    How about a police car/fire engine light. They used to make helmets
    for kids with those lights on them. Or one of those toy robots.

  10. Steve Sousa

    Steve Sousa Guest

    in message ..
    What about one of those lamps that flicker like a candle?
  11. John Fields

    John Fields Guest

    A 100 watt incandescent lamp turned on and off periodically will do
    it. The trick is, you have to locate the lamp on one side or the
    other of the PIR motion detector's sensitive region so that the heat
    from the lamp will only get focused on one of the PIR sensor's two
  12. Jeff Wisnia

    Jeff Wisnia Guest

    There's no manufacturer's name on them to lead you to a web site where
    you can find or ask for information about them?

  13. Well, I went out there today and went on a walk-thru of the new bldg
    with the other honchos. I found that the light switches have _two_
    small buttons, side-by-side, labeled "I" and "II". These are set up so
    that one of them lights the center tube of the three-tube fluo light,
    and the other lights the two outer tubes of the fluo light. So you can
    press both buttons for all three. Unfortunately there's no way to
    rapidly toggle these on and off, because they're like a ball point pen,
    they're click on, click off. And they're small enough so that if you're
    trying to hit them quickly, you're likely to press the wrong one, or
    both of them.

    So it looks like your idea of rapidly toggling these, sadly, isn't going
    to work. And _every_steenking_room_ has them! Damn!
  14. Hey, YEAH! That's a good idea! Actually, I've found the perfect
    candidate. As we were doing the walk-thru, we saw this small gray-brown
    spot of fur fly by, below our feet. It was a little field mouse that,
    for some reason, ran inside. Well, later, there he was again, flitting
    down the hallway, more scared of us than we were of him! EEK!

    Looks like we need to get a cat or two. The exterminator put traps
    outside each building, but apparently, from this experience, they're not
    doing the job!
  15. The ones I've seen have two electrodes in neon gas, and don't produce
    enough IR to do the job.
  16. For the last half hour, I've been googling for motion sensing light
    switches, and I still haven't come across anything that looks remotely
    like the ones in this new bldg. I'm going to keep searching until I
    find one that at least _looks_ like them. So far, I know that they're
    not Leviton, Zenith or GE.
  17. Ah-HAH! I'm finding out more and more about these sensors. So even tho
    they're only three leads, ground, power and output, they have more than
    a single sensor inside? That's good to know, thanks. Maybe that's why
    J.T. suggested two lights spaced 3' apart.
  18. John Fields

    John Fields Guest

    Yes. AFAIK there are three types of materials used in the sensors:
    lithium niobate, poled polyvinylidene fluoride, and a ceramic of some
    sort. Almost all of them internally use two tiny rectangular sensors
    which generate an electrical signal when they're heated, (or cooled)
    and they're connected differentially so that if they're both heated or
    cooled at the same rate the net output from the pair will be zero. A
    lens is used in front of them so that as a warm object moves across
    them the image will be focused when it hits them, and as the spot
    traverses the pair it generates the desired output, which is usually
    cap-coupled and severely bandwidth limited and eventually used to
    makes the yes-no decision about whether to turn on the lights, or
    detonate the bomb, or whatever.

    That's good to know, thanks.

    You're welcome. :)
    More than likely, but you can do it just as well with a single
    off-normal lamp, and I'd put it farther away from the center line than
    18 inches just to make sure it's not hitting both sensors equally.

    My 100 watts is probably way overkill, too, since we humans radiate
    about 100 watts from a rather large area, so you could for sure get by
    with less from a point-ish source like an incandescent lamp.
  19. Guy Macon

    Guy Macon Guest

    I have done a lot of work with security system PIR sensors.
    The typical design uses a single sensor and a molded multiple lens
    array so that the sensor "sees" what you would see if you punched
    a few holes in a sheet of cardboard and held it a couple of feet
    in front of you. The "motion sensing" is really a warm body
    either being in front of the "hole" or between two of them. The
    sensor then takes the signal. low pass filters it so that no 60Hz
    gets through, takes out the DC with a series capacitor, then
    rectifies the signal and runs it into a comparator threshold
  20. Rich Grise

    Rich Grise Guest

    on Monday 12 July 2004 04:51 pm, Watson A.Name "Watt Sun - the Dark Remover"
    Then again, you could just stay awake. ;-)
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