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Motion sensing

Discussion in 'Sensors and Actuators' started by Gerald Brown, Aug 1, 2021.

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  1. Gerald Brown

    Gerald Brown

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    Nov 8, 2017
    We have a need to design and develop of source a sensory circuit that detects when an aluminum tube of 1.5" diameter crosses or approaches the sensor. The aluminum tube should be initially detected at a distance of 15 feet with a very narrow pattern from the sensor to prevent false triggering. Ideally the sensor should be IP68 weather rated.

    All advice is greatly appreciated.
    Gerry
     
  2. Bluejets

    Bluejets

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    Oct 5, 2014
    Does the tube approach from just one direction?
    If so, is that direction on the same plane or a z axis?
    Is there any other movement in the vicinity of the detect zone of 15ft?
    How large is the tube in height?
    Are there environmental restrictions imposed if any type of light sensing is involved?
    Does the tube need to locate directly on the sensor itself?
    Is there any other obstacle in the path of the tube both before and after the desired movement?
     
  3. Gerald Brown

    Gerald Brown

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    Nov 8, 2017
    I appreciate your questions. In fact, the sensing device (alarm) will horizontally approaching as stationary aluminum tube which is perpendicular at 90 degrees to the approaching sensor device. The tube is approximately 1.5 inches in diameter, possible larger, and ten feet in length, again, at the same vertical elevation as the sensor and directly ahead. The intent is to design a circuit with sensor that is somewhat directional to minimize false indications and provide a substantially high db audio warning of predicted collision. Movement or the sensor toward the aluminum cross member tube is minimal, usually no more than one to two miles per hour.
     
  4. Gerald Brown

    Gerald Brown

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    Nov 8, 2017
    Sorry, I didn't answer a couple of your questions. Yes, approach is from a single and perpendicular direction to the tube. There is no other movement generally in the vicinity of the tube. No environmental restrictions to the type of light involved but the device will normally operate in full sunlight. No, no obstructions of any type between the sensor and aluminum tubing.
     
  5. Bluejets

    Bluejets

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    Oct 5, 2014
    Operating in full sunlight can make any type of light sensing more complex.
    Suns rays tend to interfere with just about everything along those lines and needs probably a lot of work to be consistent.

    Arduino "time of flight" minature (radar) sensors are dead accurate and with a relatively small sense angle that can be worked with but only up to around 2 metres.

    Again Arduino, ultrasonic sensors can be used up to (claimed) 4 metres and narrowing the send and receive would need some work.

    Biggest problem is your requirement for IP68.
    Nothing here comes close and any type of enclosure would intefere with the signal.

    Only other thing I can think of would be some type of mechanical connection on the tube referencing the finish point via an encoder.
    In this instance IP68 would be possible.
     
  6. Gerald Brown

    Gerald Brown

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    Nov 8, 2017
    I suspected the IP68 ambition could present a challenge. It may be best to provide an explanation of the actual goal. Our boat has a bimini cover that can be raised for shade and is supported by a 1.25" square aluminum frame. The boat is normally stored upon a Shore Station that hydraulically lifts the boat when not in use to prevent fouling. The Shore Station is covered by a vinyl cover, itself supported by an aluminum tube framework, including cross members. It is easy to forget to lower the bimini cover when returning to the Shore Station which causes damage, most often to the bimini support frame or fixtures. My goal is to create a warning device that would audibly announce the approach to the Shore Station if the bimini is in the raised position. Providing an alert when the boat is ten to twelve feet away from the Shore Station is adequate because the approach is normally at idle speed of about one mile per hour. This distance would provide adequate warning of an impending contact between bimini and Shore Station to avert damage. This is a single location application, that is, I'm only concerned with a single specific marine craft and it's home Shore Station. The sensor or parts of the sensor could be mounted on the Shore Station or boat. I did wonder about the possibility of a fairly directional emitter being attached to the Shore Station that would direct a beam outward to be intercepted by a receiver attached to the bimini which would only be triggered if the bimini is raised. Hopefully this provides a better overview of the application. Gerry
     
  7. shumifan50

    shumifan50

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    Jan 16, 2014
    I would be tempted to use a gps module as these are accurate to 10m and your project, seemingly, would be comfortably serviced by that level of accuracy. Once the alarm gets triggered, it can be reset so it does not trigger again until you have gone out of range. The gps modules available allows uart etc interfaces and would be a lot cheaper than boat repairs. Include a button to register 'home' in case you move around. These modules also, typically, provide speed and altitude, the latter being useless for your project. I don't know whether Microchip have libraries for their micro-processors, but Arduino does. My personal preference would be an ESP32 processor that also provides wifi, which could be accessed from your mobile phone/device, which might be useful for other purposes.
    Most important is that the gps antennas are weather proof and can have quite long interface cables, so the micro can be inside the cabin.
     
  8. Bluejets

    Bluejets

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    Oct 5, 2014
    Possibly think about using an off-the-shelf passive infrared detector, angled such that it will only detect the top of the bimini.
    Note that most of these units detect at an angle to the incoming traffic, not straight on as one might imagine.
    They also do not like direct sunlight on the front lense so may need "shading" however they are completely weatherproof.(not waterproof)

    Only issue is the tide goes up and down.

    To overcome that, there are 12v versions which one could mount on the raised bimini to detect the shore station.
    However, then there are the waves to contend with.

    Does everyone approach the shore station with their eyes shut...?? :):)

    pirSensor.jpg
     
  9. Gerald Brown

    Gerald Brown

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    Nov 8, 2017
    No, eyes wide open, memory less so. I ordered one of the automotive back up sensors. Four button sensors and control box with audible and LED alerts for $18, not a bank breaking gamble. It may be lacking on range, would like to sense at 15' distance or so but will test it without drilling holes for sonic buttons. When used in automobiles or trucks, these are wired to activate with back up lights. I instead need for this to activate only in forward and when the bimini is in the raised position. Docking a 108 inch wide pontoon boat in a framework that has only four inches clearance on each side is the focus, much like "greasing" a landing for a pilot. The mental focus is on alignment and whether the bimini is raised or not quickly becomes secondary to preventing damage to the pontoons when entering an aluminum framework of the Shore Station. I have a friend, opthalmologist actually, who has done the same thing multliple times...my lower IQ isn't solely to blame.
     
  10. Bluejets

    Bluejets

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    Oct 5, 2014
    Same pensioners club eh?....:):)

    I think you'll find your sonic device will have a rather large "viewing angle" , whereas the pir sensor I mentioned can be "blinkered" ( much like an old draught horse in the horse and buggy situation)
    I have seen some which will actually have small clip in front sensor "blinker panels" expressly for that particular senario.
    Failing that any old piece of black tape with a half decent sticky bit would do as an experimental temporary fix.
    Also you can adjust most for a range up to 12 metres and there is sensitivity adjustment on the more expensive units. ($50 plus)
     
    Last edited: Aug 7, 2021
  11. Gerald Brown

    Gerald Brown

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    Nov 8, 2017
    Bluejets...you are totally correct. Set the sonic up in my shop to test. The viewing angle isn't as negative as the maximum range. I don't know if this is a lower powered unit or if all are similar. Are there any specific PIR units that you recommend to test. There is another technology that I've wondered about, the pedestrian detection and "vehicle following" radar type units installed on the front of many new automobiles? I don't know pluses and negatives of these or if a way to adapt to my application. They have greater range obviously and good weather/water protection.
     
  12. Bluejets

    Bluejets

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    Oct 5, 2014
    They'd be the same as what you have already tried(ultrasonic).
    The PIR I showed is only around $20 mark so would be ok to test with, possible be the final coice as well.
     
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