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Thread: Finding the right sensor for a photography project

  1. #1
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    Finding the right sensor for a photography project

    Hello

    I have been feeding crows by placing walnut kernels on my window sill for a few months. I thought it would be an easy and fun project to place a digital camera next to the window, and let it automatically take a photo whenever a birds flies by to take the snack with him.

    My first try was using a laser and a light sensor. The walnut was placed to break the laser beam and as soon as the birds would remove the walnut, the camera would be triggered. This didn't work too well, because the birds seemed to not like the laser-light and stopped getting the snacks.

    So my current thought is, I should use something different to trigger the camera. Like a switch that activates when the walnut is removed. A low pressure sensor or just a button which is easily released by a small weight (a walnut weights about 2-3 gram). I looked online, but couldn't find a switch for what I am looking for. I was also looking for pressure sensors but they usually work from 10 gram+. Maybe I'm just looking for the wrong components.

    Does anybody have a suggestion on what components could help me to achieve this?

    I have a Teensy 3.6 and 3.2.

    p.s. This is my first post in this forum, so I hope I did everything right

    Thanks
    Sam

  2. #2
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    Maybe place the mutt on top of a mems microphone? as soon as the mutt is being moved this should cause a use contact sound. Trigger the camera from a sound level detector?


    PDont think you even need an MCU for this

  3. #3
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    Why not use IR beam break? And you could use a remote control IR receiver as a way to reject external/extraneous IR. Shield the beam from the crow's sight.

    Another approach, create a small platform that is held up by springs from a base and have a contact that closes when there is enough weight on the base. Maybe use a microswitch. The springs are sized to allow closure at about the weight of crow.

  4. #4
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    Maybe place the mutt on top of a mems microphone? as soon as the mutt is being moved this should cause a use contact sound. Trigger the camera from a sound level detector?
    I didn't think about this before, interesting idea. However, I'm not sure if the reaction time will be fast enough. Will try it!

  5. #5
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    Why not use IR beam break? And you could use a remote control IR receiver as a way to reject external/extraneous IR. Shield the beam from the crow's sight.

    Another approach, create a small platform that is held up by springs from a base and have a contact that closes when there is enough weight on the base. Maybe use a microswitch. The springs are sized to allow closure at about the weight of crow.
    Also had the idea with the IR beam. However, I'm not sure if this would work in bright daylight.

    The microswitch is basically what I had in mind. I will try to find some less bulky ones and give it a try! Thanks

  6. #6
    Senior Member+ MichaelMeissner's Avatar
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    I don't know if a Teensy 4.1 is up to the task, but I am reminded of this youtube video from a 2012 conference about using Python to recognize squirrels and then train water guns at said squirrels (and of course the reactions of the squirrels):


    There are smart cameras that are supposed to allow you to choose things to look for without overwhelming the microprocessor:

  7. #7
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    Quote Originally Posted by SamKre View Post
    Also had the idea with the IR beam. However, I'm not sure if this would work in bright daylight.
    If you use light "tunnels" on both emitter and receiver you can eliminate extraneous radiation (i.e. light and IR). The two tunnels have to be aligned. I have used drinking straws and epoxy.

  8. #8
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    What about a PIR motion detector? It emits nothing that could distract or blind the birds.
    https://learn.adafruit.com/pir-passi...-motion-sensor

    I also thought about placing the snacks on a condutive plate and connect this to a sensor input, but then there will be very weak oscillating electric signals on the snacks. Even stronger signals with https://github.com/AdrianFreed/FastTouch
    Maybe this distracts the birds. So electrical sensing may not really be an option.

  9. #9
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    Quote Originally Posted by SamKre View Post
    Hello

    I have been feeding crows by placing walnut kernels on my window sill for a few months. I thought it would be an easy and fun project to place a digital camera next to the window, and let it automatically take a photo whenever a birds flies by to take the snack with him.

    My first try was using a laser and a light sensor. The walnut was placed to break the laser beam and as soon as the birds would remove the walnut, the camera would be triggered. This didn't work too well, because the birds seemed to not like the laser-light and stopped getting the snacks.

    So my current thought is, I should use something different to trigger the camera. Like a switch that activates when the walnut is removed. A low pressure sensor or just a button which is easily released by a small weight (a walnut weights about 2-3 gram). I looked online, but couldn't find a switch for what I am looking for. I was also looking for pressure sensors but they usually work from 10 gram+. Maybe I'm just looking for the wrong components.

    Does anybody have a suggestion on what components could help me to achieve this?

    I have a Teensy 3.6 and 3.2.

    p.s. This is my first post in this forum, so I hope I did everything right

    Thanks
    Sam
    I think a neat approach would be to build your own switch with some brass sheet stock from the local hobby shop:

    Code:
      
    T___________NUT_
              ^____________G
    The 'T' is a terminal for a switch input on your Teensy. Set the input to INPUT_PULLUP mode and connect the other 'G terminal to Teensy ground. You should be able to adjust the brass nut holder so that the switch is closed when the nut is in place and open when the crow removes the nut. This switch would only take the brass stock, a piece of board and two screws. The rest is software-which should include debouncing and possibly multiple exposures depending on how fast you can trigger your camera.

    I may try to capture some pics of my own with my OV7670 library for the T4.1. The goal would be to use the motion detection function to watch for the birds. I would also have to put in a time gate as the motion-detection algorithm gets a lot of false triggers at dawn and dusk, when the camera output is noisy as the OV7670 tries to adjust auto exposure for the changing lighting conditions.

    Instead of getting pics of crows, I might point the camera at my wife's hummingbird feeder. If I start putting out walnuts, I'll attract squirrels, and they cause very noisy barking fits by our dog.

    If the pictures are more important than the project, you could just buy a $40 trail camera with motion detection, Hi-def JPEG pictures and SD card storage.

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