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Touch sensor to activate light for set amount of time

Discussion in 'Sensors and Actuators' started by 3n008, Dec 20, 2015.

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  1. 3n008

    3n008

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    Dec 20, 2015
    I need to create a circuit where a touch sensor (activated by pressure of a non conductive object) will trigger a light to to turn on for a set amount of time.

    I am a total newcomer to circuits (although I remember some of the basics from high school AP physics).

    I have been researching on Google and Youtube, and have come across some great tutorials but I still have some questions which probably seem very basic so please bear with me.

    1. My first question has to do with the touch sensor. I found this online:
    https://www.adafruit.com/products/1075?gclid=CMee4YLJ68kCFc9gfgodZSIFOQ

    From what I gather, when force is applied, this acts like a switch and will complete a circuit. When the force is removed, the circuit is then incomplete. Is this correct?

    2. My second question has to do with triggering a light, or basically completing the circuit for a set amount of time. I haven't found anything about this online but I assume there is some component that can help me do this. If someone could point me in the right direction that would be great.
     
  2. Alec_t

    Alec_t

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    Jul 7, 2015
    Welcome to EP!
    No. It varies its resistance in response to force. You would then have to use that resistance change to turn a transistor on/off and hence control a circuit load.
    If you just want something to switch on or off when you touch it there is a much cheaper solution, relying on skin resistance of a finger. But if the object exerting the force must be non-conductive, then why not use a sensitive micro-switch, e.g. lever-actuated?
    How long do you want the light to stay on?
    What type of light? Battery or mains power?
     
  3. 3n008

    3n008

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    Dec 20, 2015
    Thanks for the reply.

    I googled for micro switches. Sounds like that is what I need. A lot better than a touch sensor.

    To be more clear about my project, I need to activate this circuit when a golf ball rolls over the switch.

    So actually I need this setup to control a number of things. In one instance it might be a light that would remain on for a few seconds, in another instance it might be some device that plays a sound affect, and in another instance it would turn a motor on for about 30 seconds.

    I am not sure if it will be battery or mains power at this point.
     
    Last edited: Dec 21, 2015
  4. hevans1944

    hevans1944 Hop - AC8NS

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    You could just drill a hole and mount a photo-transistor or photo-diode under it, using ambient light to illuminate it. When the golf ball rolls over the hole it will temporarily block light to the sensor beneath the hole causing a change in sensor output. The amount of change will depend on how much ambient light is present and the particular photo-sensitive device and circuit you use. I would NOT recommend using a light-dependent resistor (LDR) for this because their resistance varies all over the place as a function of illumination intensity. Depending on how many golf ball sensors you need, a photo-transistor may be all you need. A small Microchip PIC micro-controller, one per sensor, can be used to detect the change in sensor signal and provide a time-controlled output function to energize a relay, a MOSFET, or an isolated solid-state switch. You could build a circuit board containing a photo-sensor, the PIC, and output device (transistor, electromagnetic relay, MOSFET, solid-state switch, whatever) with a foot-print about the size of a coin using SMDs. Two wires in for DC power, two wires out to switch the load.

    Unless you can find a boatload as surplus for a few pennies each, micro switches are way overkill for sensing the passage of a rolling golf ball. And they can be finicky to mechanically adjust for reliable operation.

    What, exactly, are you building? A miniature golf course?

    Hop
     
    Martaine2005 likes this.
  5. 3n008

    3n008

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    Dec 20, 2015
    Hi, I'm building a prototype for a patent, not a miniature golf course. I am lacking the funds now to hire an electrical engineer AND deal with patent lawyer fees. Fortunately I think the technology is simple enough for me to EVENTUALLY figure out, so I am having a go at this myself.

    Thanks for the idea regarding a photo transistor.

    Now looks like I need to Google about all the things you mentioned to try to learn how to put them all together.
     
  6. GPG

    GPG

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    Sep 18, 2015
    You can get interrupted or reflective optical sensors.
    Google both terms. Also the emitter can be coded to reduce the effects of incident light .Remote controls all do this. Most remote controls output the code on a carrier further reducing incident signals and allowing higher peak power/range.
     
    Last edited: Dec 21, 2015
    hevans1944 likes this.
  7. hevans1944

    hevans1944 Hop - AC8NS

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    Welcome to the real world where patents don't really help the little guy at all. With a phalanx of well-paid lawyers, large corporations scoop up patents and use them to silence competition or bury technology unfavorable to their current business model. You do have a business model, don't you? Without a well-oiled business model the sharks will eat you alive. Even with a good business model, you can fail for lack of financing for production after sales roll in.

    As for patent prototypes, these are not necessary (at least for a US patent). All you need is a clear description, such that an ordinary person skilled in the art of whatever your patent describes, can reproduce whatever it is you seek to patent. In return for "spilling the beans" and letting the whole world know about your "invention" you are granted exclusive rights for a limited period of time to make, manufacture, promote, sell, yada, yada, yada in the country that grants your patent. If you want "protection" around the world (China comes to mind) you must file a zillion more patent applications.

    Now here's the rub, and where the little guy always loses: You must aggressively defend your patent against all infringement using your own funds. That means your patent must be providing oodles of dough first, before it is "stolen" and commercialized elsewhere. Good luck with that.

    Is there a viable alternative to patent "protection" of your intellectual property? You bet! It is called a "trade secret". You build it and they will come, but you do not divulge how you built it. There is an entire industry out there devoted to protecting (and also reverse engineering) trade secrets. You should investigate whether your idea can be "protected" the same way before spending a lot of time and money securing a patent. In the rapidly changing world we all live in now, sometimes it only takes a few weeks for today's brilliant idea to become tomorrow's has-been. The idea is to get your product to market first, make a pile of cash from it, then move on to the next great idea. Do this after your first idea has been "stolen" and driven into the ground by price competition from unlicensed knock-off products. Remember, in securing a patent, you basically tell all and practically invite theft of your idea.

    BTW, at least in the United States, you can file for a patent without the services of a patent attorney. Takes a lot of due diligence on your part to find out how, but it can be done.
     
    Martaine2005 and Alec_t like this.
  8. Alec_t

    Alec_t

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    Everything Hop says above about US patents applies to UK and European patents too. In particular, there's no legal requirement for a working prototype. But if you're determined to apply a patent, make absolutely sure that you don't publicly disclose anything you plan to patent-protect, until your application has been filed with the patent office. Such prior disclosure would invalidate the patent.
     
    Last edited: Dec 21, 2015
    hevans1944 likes this.
  9. davenn

    davenn Moderator

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    and as an observation ... since you would likely to be using all standard technology ... ie ... nothing new and revolutionary, it unlikely to be patentable anyway
    since a zillion people have already played with that way to do things

    D
     
    Martaine2005 likes this.
  10. hevans1944

    hevans1944 Hop - AC8NS

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    What you can patent or not all depends on your particular patent examiner and what you are claiming to have invented that is different from prior art. If you are denied on your first attempt, you can make changes (usually in your claims) that may satisfy the patent examiner or a different examiner. It can be an expensive process if lawyers are involved, with no guarantee of success. Here is an example: my former supervisor and I filed for a patent that, if awarded, would be assigned to our employer. The patent application describes a novel high-voltage, high-current, high-speed, optically triggered switch that switches on much like a silicon controlled rectifier, except with nanosecond IR illumination. The work was a result of research paid for by US taxpayer dollars and was a spin-off of earlier (unsuccessful) government research at Sandia National Laboratories (SNL) which was also paid for with taxpayer dollars in the 1990s. Our initial patent application was denied and the patent examiner cited "prior art" at SNL as the reason.

    My former employer may or may not decide to pursue the patent by changing some of the claims. There is no doubt that prior art exists, but our device is rather unique and not at all like the SNL devices. It was so unique that it won a 2015 R&D 100 award from R&D Magazine for innovative research. Neither my former boss nor I are promised any monetary reward if the patent is eventually granted. After all, our salaries were paid at the time for the work being done, so (at least in Ohio) this is regarded as "work for hire" by our employer to which we voluntarily assigned the patent rights. It would be interesting if our PCSS device eventually evolves into a commercial product, but I doubt that I will have any involvement in that. Still, it was a pleasant way to end my career as of December 31, 2014.

    Best luck to @3n008 on your endeavors.
     
  11. 3n008

    3n008

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    Dec 20, 2015
    I think the reflective optical sensor is the best option given the physical requirements I need.

    I googled and found this:
    https://en.wikipedia.org/wiki/Photoelectric_sensor

    And this product:
    http://www.galco.com/buy/IDEC/SA1E-PP2?source=googleshopping&gclid=CJ_Z8fzU88kCFYaCfgodBDkGkw

    The output is either PNP or NPN.

    Could I set up the Microchip PIC micro-controller to detect a change in the signal and have the rest of my setup be as Hevans described?
     
  12. GPG

    GPG

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    Sep 18, 2015
    Last edited: Dec 24, 2015
  13. AnalogKid

    AnalogKid

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    Jun 10, 2015
    Is the golf ball rolling down a tube or tunnel or chute of some kind? In other words, is it confined to a narrow space as it passes the sensor?

    ak
     
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