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Newbee needs help with design

  1. Feb 18, 2009 #1
    Hi everyone. I am trying to design a timed vibration device that I can use for my son. He has a mild form of autism and he seems to need continual sensory input. We are attempting all different type of strategies but I have an idea I would like to try but do not have the needed skills. So, here I am. What I am wanting to create is a cyclic vibration device that is small enough to be attached to the wire arm of his glasses similar in concept to a chochlear implant for the deaf. I chose the arm of his glasses because 1. the motor would be small enough to not be stupidly obvious. 2. it would be located at or rest against the mastoid bone which is located behind and/or below the ear. This would give a vibrational stimulus that is both "auditory" and physical/tactile. 3. He wears his glasses always and would not need to try to remember to carry something else that could be easily lost. So, I am envisioning a small offset vibrational motor (like the kind used in pagers) because they are small, require minimal energy, and do not produce a lot of heat energy. This could be powered by a watch battery if possible. Ideally, there would be something like an cyclical timer/ 551 chip / a slow filling capacitor that would act like a timer. All of the components would, hopefully, be embedded into a resin base in order to make it fairly durable. I am envisioning a mold that I can take the old battery out and easily put in a new one. I realize this may be a tall order but I would appreciate any help possible. Thank You
     
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  3. Feb 18, 2009 #2

    dlgoff

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    Welcome to Physics Forums midwest_medic. Can you give a little more detail? How often would you like the vibration to occur and for what length of duration? Do you have a frequency of vibration in mind? Are you wanting this on both sides of the head or just one side? Would a small speaker (or pizoelectric device) work instead of a motor?
     
  4. Feb 20, 2009 #3
    Hi, thanks for the welcome and q's. So, let's see...1-2 sec duration every 5-10 sec's. Frequency? hmmm, hadn't thought of that. I assumed (you know what that gets you. LOL) that the small motors in pagers were pretty much the same frequency. Micro vibrating motors operating 10k-50k rpm? Thinking of something like this when I began to envision:
    http://www.globalsources.com/gsol/I/Vibration-motor/p/sm/1008010618.htm
    or
    http://www.73.com/a/0185.shtml

    Yes, pizoelectric device would also work. Hope this helps. Again, thanks for your assistance.
     
  5. Feb 20, 2009 #4

    berkeman

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    Welcom, medic. I think the pager/cellphone buzzer is probably a good approach, as long as it vibrates with about the right amplitude for you (not too hard).

    To calculate the battery life, look at the Amp*Hour (Ahr) rating, and compare that to your circuit's current draw. Like, the motor you linked to is 90mA when running at 3V, so to get 10 hours of operation at 10% duty cycle would take a battery with this capacity:

    0.090A * (1/10) * 10hr = 0.09Ahr.

    So if you used two type N batteries (1000mAhr each) in series to make the 3V, you could get about

    1000mAhr / 90mA = 11 hours of motor running, or about a week of daytime operation.

    But if you use smaller watch/button batteries, you may end up having to change them pretty often. Can you maybe build this into a baseball cap instead of the glasses? Type N batteries are small, but not compared to glasses.

    http://en.wikipedia.org/wiki/Battery_(electricity [Broken])

    Also, for the timer circuit, it would probably be best to use a simple digital timer circuit, probably based on the 74HC4060 integrated circuit chip. The 4060 has a built-in oscillator (you can connect a crystal or RC circuit to it to define the oscillation frequency), and a long ripple divider chain, to get you low frequencies with long periods like the 1-10 seconds that you want. You could do a little simple logic to generate a 1-second pulse every 8 seconds, for example. Here's the datasheet for the 4060:

    http://www.fairchildsemi.com/ds/MM/MM74HC4060.pdf

    .
     
    Last edited by a moderator: May 4, 2017
  6. Feb 20, 2009 #5

    dlgoff

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    Last edited by a moderator: Apr 24, 2017
  7. Feb 20, 2009 #6

    berkeman

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    He's trying to stimulate the boy, not blow his head off! :eek:

    J/K. But you'd at least need to stuff that thing with epoxy or something to get the noise down to something more subtle, eh? The lower power is attractive.

    medic -- have you gotten a few things to try out to see how they feel and sound? Like your motor and dlgoff's buzzer/beeper?
     
    Last edited by a moderator: Apr 24, 2017
  8. Feb 20, 2009 #7

    dlgoff

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    Yea, I was going to mention that it would probably be too loud. I was mainly looking at the frequency and current spec. I was looking at other cell phone buzzers and they were also loud. Most of them had to be bought in large quantities from China.
     
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