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    PIR sensor with cylindrical coverage

    hi,

    I want to use pir sensor under a razor wire fence on my home's boundary which is a cylinder of 50 feet long. Instead of using 100 angle coverage I want pir sensing area of cylindrical shape of .5 meter diameter. How can I change my pir sensor's coverage area and pattern?

    thanks,
    ravi

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    how to change pir sensor coverage angle?

    hi,
    i know pir sensor coverage angle is 180 or 110 usually.
    is there a way to change the coverage angle?

    thanks



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    Re: how to change pir sensor coverage angle?

    A narrow coverage angle is established by using optics in front of the detector, e.g. plastic film fresnel lenses or parabolic mirrors. Sensors with a narrow angle of a few degrees are made for burglar alarms.

    A cylindrical sensing area isn't feasible, it's conical by nature. (Unless you are utilizing a surface mirror of 0.5 m diameter)



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    Re: how to change pir sensor coverage angle?

    You might be better off with an interruptor type sense,
    like they used to use on garage door safety systems
    (maybe still) - co-located emitter and detector, and a
    far-end mirror. The emitter has the beam shape optics
    and the detector some concentratring optics perhaps.

    I think getting 49-1/2' of passive infrared detection
    range is a real stretch. But a laser diode or well focused
    high power LED source, you can get much more range
    (because much more initial optical power).

    Infrared LEDs would make it human-invisible other than
    the hardware.



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    Re: how to change pir sensor coverage angle?

    Quote Originally Posted by dick_freebird View Post
    You might be better off with an interruptor type sense,
    like they used to use on garage door safety systems
    (maybe still) - co-located emitter and detector, and a
    far-end mirror. The emitter has the beam shape optics
    and the detector some concentratring optics perhaps.

    I think getting 49-1/2' of passive infrared detection
    range is a real stretch. But a laser diode or well focused
    high power LED source, you can get much more range
    (because much more initial optical power).

    Infrared LEDs would make it human-invisible other than
    the hardware.
    are you talking about laser based security alarm? can you please explain this "interrupter type sensor? any part name etc? thanks.



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    Re: how to change pir sensor coverage angle?

    By interrupter we mean that rather than look for IR (heat) radiating from an object to trigger the alarm, instead a beam of light is generated and targeted at a sensor along the path being tested. If a body comes between the light source and sensor it breaks the beam and therefore triggers your system. The advantage is much greater range from a very simple and inexpensive system and if you use IR LEDs as the source, it is invisible to the eye. The drawback is it works in straight lines so if the boundary has curves you have to bend the beam with mirrors or break it into smaller sections.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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    Re: how to change pir sensor coverage angle?

    Quote Originally Posted by betwixt View Post
    By interrupter we mean that rather than look for IR (heat) radiating from an object to trigger the alarm, instead a beam of light is generated and targeted at a sensor along the path being tested. If a body comes between the light source and sensor it breaks the beam and therefore triggers your system. The advantage is much greater range from a very simple and inexpensive system and if you use IR LEDs as the source, it is invisible to the eye. The drawback is it works in straight lines so if the boundary has curves you have to bend the beam with mirrors or break it into smaller sections.

    Brian.
    in short, is this something you are suggesting ?

    https://www.electronicshub.org/laser-security-system/

    I am a computer science student and novice in electronics. Hence looking for something with example.
    thanks.



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    Re: how to change pir sensor coverage angle?

    People are talking about photo electric sensor in through beam mode, see e.g. https://en.wikipedia.org/wiki/Photoelectric_sensor

    In contrast to your linked laser pointer / LDR sensor example, reliable sensors are using a modulated (pulsed) light source. This allows to suppress ambient light and simple tamper attacks.



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    Re: how to change pir sensor coverage angle?

    Quote Originally Posted by FvM View Post
    People are talking about photo electric sensor in through beam mode, see e.g. https://en.wikipedia.org/wiki/Photoelectric_sensor

    In contrast to your linked laser pointer / LDR sensor example, reliable sensors are using a modulated (pulsed) light source. This allows to suppress ambient light and simple tamper attacks.
    is this be good for me ? https://www.autonicsonline.com/produ...=755&limit=200



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    Re: how to change pir sensor coverage angle?

    That is exactly the thing but it only has a range of 10m (about 30 feet) so you would need more than one to give the 50' length you need.
    With a little effort you could make one with the same or longer range for a fraction of the cost.

    Brian.
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    Re: how to change pir sensor coverage angle?

    Quote Originally Posted by betwixt View Post
    That is exactly the thing but it only has a range of 10m (about 30 feet) so you would need more than one to give the 50' length you need.
    With a little effort you could make one with the same or longer range for a fraction of the cost.

    Brian.
    what is tweak required for increasing range ?
    moreover I need a circuit for using this sensor for my task. any idea where I can get the circuit diagram?



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    Re: how to change pir sensor coverage angle?

    I wouldn't 'tweak' a commercial product, I would start from scratch.

    I assume this is just a one-off project and not for mass marketing so I would suggest you get hold of an old scrapped TV or VCR and salvage the remote control receiver from it. It will work just as well as any commercial detector product and they normally have the necessary pulse filtering built into them. For the transmitter you need a high output IR LED and an NE555 timer IC. The range is mostly determined by the radiation angle and detection angle of the optics, you need lenses or reflectors to focus the beam as narrow as possible.

    The idea is the NE555 produces high current pulses at about 38KHz frequency and these drive the IR emitter LED. The LED flashes 38,000 times a second!
    The receiver sees the presence or absence of the pulses and gives you a high or low output that can be used to sense whether the beam has been broken or not.

    The reason for pulsing at high frequency is that IR light can come from many sources, including sunlight so you need a method to distinguish your beam from background sources. In the IR receiver modules there is a filter to reject anything that isn't flashing at that speed and a timer circuit that keeps the output steady between the pulses if they are present.

    You will find it easiest to use a laser LED to produce a sharp narrow beam instead of a normal LED and optics but they normally operate in visible red light so the beam would be easy to see.

    Brian.
    PLEASE - no friends requests or private emails, I simply don't have time to reply to them all.
    It's better to share your questions and answers on Edaboard so we can all benefit from each others experiences.



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    Re: how to change pir sensor coverage angle?

    Quote Originally Posted by betwixt View Post
    I wouldn't 'tweak' a commercial product, I would start from scratch.

    I assume this is just a one-off project and not for mass marketing so I would suggest you get hold of an old scrapped TV or VCR and salvage the remote control receiver from it. It will work just as well as any commercial detector product and they normally have the necessary pulse filtering built into them. For the transmitter you need a high output IR LED and an NE555 timer IC. The range is mostly determined by the radiation angle and detection angle of the optics, you need lenses or reflectors to focus the beam as narrow as possible.

    The idea is the NE555 produces high current pulses at about 38KHz frequency and these drive the IR emitter LED. The LED flashes 38,000 times a second!
    The receiver sees the presence or absence of the pulses and gives you a high or low output that can be used to sense whether the beam has been broken or not.

    The reason for pulsing at high frequency is that IR light can come from many sources, including sunlight so you need a method to distinguish your beam from background sources. In the IR receiver modules there is a filter to reject anything that isn't flashing at that speed and a timer circuit that keeps the output steady between the pulses if they are present.

    You will find it easiest to use a laser LED to produce a sharp narrow beam instead of a normal LED and optics but they normally operate in visible red light so the beam would be easy to see.

    Brian.
    yes i will built it from scratch.
    as i said i m not from electronics background. i do not have such scrapped tv or vcr. at max i can do is if any circuit diagram is available, i can implement that using breadbord, soldiering iron etc.
    so i am looking for some exisiting design. and it will run 24x7 so circuit and components should be durable and optimized in term of electricity consumption.
    where can I get such diagram? any book, tutorial, site etc for such things?
    thanks



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