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Common Clear to IR material?

Discussion in 'Electronic Design' started by amdx, Jan 21, 2013.

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  1. amdx

    amdx Guest

    I'm modifying the sensor below to limit it's detection area.

    I have put it in another housing and it is looking through a 1/2" hole.
    Now to protect it from the weather, I want to cover the hole.

    Well... I have found most common household items are opaque to infrared.

    Thinking plastic here.

    Any idea what the common wavelength of these IR motion sensors is?

    Any thought about a common item I might have or can get tomorrow
    that will be clear to IR? (and hold up to weather)

    I did find one* plastic lid to one of the wife's bowls that does a
    pretty good job. It is not labeled with an identifier, so now I'm very
    curious what it is. I will work with it tomorrow and see if I have the
    range I need.

    * she's got a cupboard full of many types of lids only one passed my test.
    PS. What is LLDPE?
    Low Low?
  2. MrTallyman

    MrTallyman Guest

    Reference the IR data sheet I posted a link to the other day.
  3. gregz

    gregz Guest

    I always used exposed Kodachrome.

    I set up mine again. Seems most sensitive dead on. I had to cut down on
    thevolume after trying duct tape, which does not work very well. Used
    something like 25k in series with speaker. I'd like another if I could get
    same channel.

  4. gregz

    gregz Guest

    The last couple of days with high winds cause cause my unit to trip. First
    problem, sensor was not mounted tight. It will still trip occasionally.
    First time I have really played with the thing after owning it for several

  5. amdx

    amdx Guest

    Yes, they are very loud and tape does not work to cut the volume, btdt.
    I'm using the receiver to trigger a call switch on a walkie talkie.
    This is so I can be 300 feet away and get an alert.
    What channel do you have?
  6. amdx

    amdx Guest

    I have kept the original Fresnel lens in place, but only because
    earlier testing showed me I had to!
    I then found out why.

    Maybe the plastic lid I have is HDPE.

    I could not make it work with polystyrene, I tried several PS objects
    and none worked. I was ready to use a CD case.

    If the lid I have doesn't pass tomorrow's testing, I'll be searching
    for HDPE to test.
    The black bag won't last long outdoors, but as a last resort, it
    would be easy to replace and stretch a couple rubber bands around every
    three months.
    Thanks, Mikek
  7. Jasen Betts

    Jasen Betts Guest

  8. Jasen Betts

    Jasen Betts Guest

    perhaps you can get a sample of IR reansparent roofing sheeting
    like Ampelite coolite
  9. mpm

    mpm Guest

    Just wondering out loud.....
    Would a Rosco photography filter work here?
    One of these might have the curve you're looking for. (??)


    Only $2.50 for the whole book (a couple hundred plastic gel filters, various colors)
  10. Owen Roberts

    Owen Roberts Guest

    On motion sensor prototypes at work a layer of 2" wide, inexpensive,
    thin, clear plastic packing tape was used. . This was to cover a one
    inch hole on a metal project box. The stuff that is 1.50 a roll at
    Walmart works fine. They did not even bother to remove the adhesive.
    Works well on sensing people. The battery powered sensors have been
    outside for four months now, in a Ohio winter, with no failures.

    A overhead transparency of the non inkjet kind would be fine as well.
    They are a little thick, so you may see some attenuation.

    The Roscoe filters are usually gelatin based on a clear substrate. .
    The water in the gelatin would adsorb at 10 microns, blocking the

  11. amdx

    amdx Guest

    I did some testing today. The unit was set under the stairsteps at
    the outdoor entrance to my business. I then looked like a nut walking up
    and down the steps and listening for the alarm. It work... almost.
    It triggered over 80% of the time maybe 90%. But it didn't work 100%.
    So, I took off the plastic lid cover I had installed for weather
    protection. The unit then work flawlessly. Oops, I had a false alarm,
    nope there were two sparrows that tripped it. :)
    I can probably make it work without the weatherproofing. I have not
    removed the cover from the original unit and it now has additional
    covering. I may need to make a weep hole in case any water does blow in.
    Some back story,
    I'm in a Marina with plenty of car and foot traffic. I needed to limit
    the area to prevent false alarms. This thing would trigger on a car 40ft
    away. One half of my possible mounting locations are eliminated
    because I can't point it towards where I work for obvious reasons.
    The opposite direction has auto and foot traffic. So I have a small
    operating area. But what I did today makes me think it wiil work good.

    I'll try a layer of black plastic bag when I get it all going.

    Thanks all, Mikek
  12. Um, isn't standard exposed photographic film largely infrared transparent?

    Many thanks,

    Don Lancaster voice phone: (928)428-4073
    Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
    rss: email:

    Please visit my GURU's LAIR web site at
  13. tm

    tm Guest

    It is to near IR but not to LW IR, i.e. 2 to 12 nm.

    BTW, you can check the NIR with some digital cameras. Use your tv remote as
    a source and insert the material to see the loss.
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