Motion Sensor/timer for Kinetic sculpture

Discussion in 'The Projects Forum' started by Simon Sawyer, Nov 3, 2017.

  1. Simon Sawyer

    Thread Starter New Member

    Nov 3, 2017
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    Hello everybody,

    I am a sculptor based in London and in the process of making a sculpture that requires a vacuum cleaner to turn on and off at regular intervals coinciding directly with a pendulum.

    I have been considering two possible options for this:
    1. A timer: I can work out how long each swing takes and use as timer to activate and deactivate the vacuum. I've had a look at timed relay switches (and actually bought one) but my electronic knowledge is so minuscule that I've got the relay to work, but it requires an additional switch of somekind and I cant figure out what!
    I like the idea of using this method as I'm hoping that control circuit can be hidden in the 'body' of the sculpture, keeping it looking as simple as possible.

    2: a beam break or similar: I have been reading up about PIR's etc but as the pendulum is does not give of heat, a beam break would be most likely be better. The pendulum would break the beam at the bottom and trigger the vacuum to start which would be on timer. I've had a look for motion activated bathroom lights as I thought this might be a (relatively) simple adaption to make; instead of trigger a light, it'd trigger a vacuum. The only issue is that appear to only be PIR's that work on infrared, and the on time minimum is 30s or so which is way to long. (I'd probably need 5-7s max)

    I'm hoping that someone can help as I've been scrabbling around desperately trying work it out using my (very very!) basic knowledge of electrical components and electronics. I've had a look through previous forum posts and have found things that might be similar, but I can't for the life of me figure it out!

    I realise that this may be a bit of a pain but hopefully there's a relatively simple solution that a noob such as myself can build! Anyway, Any help would be greatly appreciated,

    thanks
    Simon
     
  2. DickCappels

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    Aug 21, 2008
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    PIR sounds like it might be hard to control while something like a cheap red laser beam being interrupted by the pedulum would be more certain. Depending upon the ambient lighting detecting the laser beam unambiguously can be very simple to being complex.

    Can you tell us about what the pendulum looks like and the ambient lighting conditions?

    Another method to consider if your pendulum is magnetic is to use a magnetomiter to sense the pendulum. That would add a lot of complexity, the led or laser being preferred over it.

    You might also want to incorporate a timer to start your vacuum cleaner at the right phase of the swing. Hmmmm...reliability concerns come to mind about repeatedly starting the vacuum cleaner.

    The Foucult Pendulum in the image below probably uses a similar detector to keep the pendulum swinging. The reason I mention this pendulum is that its path relative to the earth varies constantly because of the earth's rotation. Could this effect affect your project?

    upload_2017-11-3_19-5-21.png
    https://www.geophysik.uni-muenchen.de/outreach/foucault-pendulum <= Link to live video feed & article about the pendulum
     
  3. Simon Sawyer

    Thread Starter New Member

    Nov 3, 2017
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    Interestingly my i was talking about Foucault with my dad the other day. The phenomenon wont affect in this case as the swing is only limited to one cycle, however i had a lot of fun reading about it. It's incredible to think that the the earth's rotation can be made visible with something so simple!
    the pendulum is a snooker ball, and the environment is not yet determined. I do know it'll be inside, in a room. The pendulum and vacuum will be housed in a simple steel structure, Imagine the narrow goal post shape to suspend the pendulum and a hoover a set distance away to catch the ball at the top of it's swing.

    I've carried out tests in my studio switching the hoover on and off manually and it works, i just don't fancy standing in a gallery for the entirety of an exhibition flicking a switch!
     
  4. DickCappels

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    Aug 21, 2008
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    There will be a delay between the time you switch on the vacuum cleaner and the time it is sucking hard enough to hold the pendulum. However, you can probably to well to just have a delay from the time the pendulum is released until it is time to start up the motor provided that the acceleration of the earth's gravity stays constant throughout the exhibition ;-)

    An adjustable delay would be pretty easy, If the vacuum cleaner runs from 220 VAC 50 Hz time granularity would be 10 millisecond if the power is switched on at an AC zero crossing -makes for cleaner and more reliable switching.

    Just guessing, can the timing be pretty sloppy? It seems the vacuum cleaner just needs to be off long enough for the pendulum to get away and then up to speed again before the pendulum comes back. Is that right?

    Do you know how long one cycle is?
     
  5. Simon Sawyer

    Thread Starter New Member

    Nov 3, 2017
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    Haha i hope the gravity does stay the same, some kind of centrifugal gravity chamber would definitely put a spanner in the works so to speak!

    I've done some tests with an approx 2.5m pendulum, the cycle is 3s give or take a millisecond here or there. Timing can be sloppy just as long as the vacuum is up to speed by the time the pendulum returns that's fine. Doing it manually I'd switch the vacuum on when the ball was at the lowest point of swing, on the first part of the cycle. This worked perfectly.

    Ideally i'd like to be able to adjust the timing so that i could shorten or lengthen the pendulum. I'm still at the testing stage and want to work out whats most aesthetically pleasing!
     
  6. gerty

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  7. Simon Sawyer

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    Nov 3, 2017
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    Hi Gerty,
    I was looking at these, but the vacuum is mains 220v. I also don't have the foggiest idea how to use it! I tried looking things up on line, but its a totally foreign language to me!
     
  8. shortbus

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    Is the vacuum/hoover sound part of the sculpture? The reason I ask is wouldn't it be better to have a vacuum tank and a solenoid valve turn it on when the vacuum is needed? This would cut down the time needed to get the vacuum necessary to catch the ball.

    If the vacuum isn't a essential part of the sculpture, could you use a metal(steel) ball and a electro magnet to catch it?

    The timing from the pendulum could be controlled with a "photo interrupter". https://www.sparkfun.com/products/9299 With it and a disc at the pendulum's pivot point with a slot or hole to do the timing.
     
  9. Simon Sawyer

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    Nov 3, 2017
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    Hi Shortbus,

    Yeah the hoover's part of it. There's a version in the pipeline for a magnetic version, but currently i'm wanting to keep it as low-fi as possible. The photo interrupter looks fun!
     
  10. DickCappels

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    Perhaps the best solution is the timer that gerty suggested in post #3.
     
  11. shortbus

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    How about using the metal ball/ electromagnet And the same time the magnet is energized a recording of a hoover running is turned on. While actually using a vacuum sounds easier, in the end turning on both a electromagnet and sound recording will be easier.

    Here's some more information on photo interrupters and how they work. http://www.rohm.com/web/global/electronics-basics/photointerrupters/what-is-a-photointerrupter/
     
  12. DickCappels

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    Perhaps the best solution is the timer that gerty suggested in post #3.
    • It is already assembled. All you have to add is a 5V power supply and some AC connectors.

    • It will be far easier for you to figure this out and connect it properly than it would be to build something from scratch.

    • It is probably the least expensive solution that you will be able to find beyond flicking the switch manually.

    • It is probably a lot safer than something one of us were to wire by hand.
    The complete instructions are on that web page (and copied here for convenience)

    upload_2017-11-3_21-45-12.png
     
  13. gerty

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  14. Bernard

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    What gives the pendulum a kick to start it swinging?
     
  15. Simon Sawyer

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    Nov 3, 2017
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    ah that's great Gerty! I'll look for something similar here in the uk.

    thanks.:)
     
  16. Simon Sawyer

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    Nov 3, 2017
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    Hi Bernard,

    It's not an auto start. Initially it'll have to be set manually, i.e ball put into the hoover nozzle. It's more about the perpetual nature of it than anything else. Although some kind of start feature would be something to work on!
     
  17. Bernard

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    Hoover seems to take about 1/2 sec. to power-up & 2 sec to release. Capture range seems to be about a cm, so need a very slow decay rate, aerodynamicaly clean with good bearing. With a 2 m, +-, pend. with a 2.5 " hollow steel ball, 40 deg. full swing, Hoover Sprint, manual timing of 2.5 sec on, 4 sec off, completed 5 cycles.
    Looks like open cycle timing should work. Fire up a 555 with 2 pots & relay & should be good to go?
    Looks like timer module, Post # 6 & 12 allows a loop mode, great.
     
    Last edited: Nov 4, 2017
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  18. be80be

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    The op is not in the US He can switch just the hot side of the vac.
    there 220 is like are 120 one hot and neutral
     
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  19. gerty

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    Don't know how I missed that the first time....
     
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